مواضيع طبيه متنوعة

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  1. منير الشيخ

    منير الشيخ قلم فضي

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    Stroke in Chinese
    [Editorial]
    Hachinski, Vladimir MD, DSc

    From The University of Western Ontario, Department of Clinical Neurological Sciences, London Health Sciences Centre – University Hospital, London, Ontario, Canada.
    Received and accepted April 25, 2006.
    Correspondence to Vladimir Hachinski, MD, DSc, The University of Western Ontario, Department of Clinical Neurological Sciences, London Health Sciences Centre – University Hospital, 339 Windermere Road, London, Ontario, N6A 5A5, Canada. E-mail Vladimir.hachinski@lhsc.on.ca
    Despite steady progress, stroke remains a leading cause of death and disability in China. The availability of high quality current information on stroke represents one of the most effective weapons in treating and preventing this great scourge. We are delighted of the launching of Stroke in Chinese.

    We welcome the joint Editors, Professors Ming Liu and Lu Chuan-Zhen. Professor Liu graduated from the West China University of Medical Sciences, Chengdu, China. She was a World Health Organization (WHO) Research Fellow at the Universities of Edinburgh, London and Oxford. Currently, she is Professor of Neurology at Sichuan University and Director of Stroke Research Unit. Professor Liu’s main interests are prevention and treatment of stroke and evidence-based neurology.

    Professor Lu graduated from the Shanghai First Medical College. He was a Fellow in Immunology and subsequently Visiting Professor at the Karolinska Institute, Sweden. Professor Lu held an International Neurosciences Fellowship from the WHO Forgaty Foundation at the University of Chicago. He is Professor and Chairman of the Department of Neurology, Chairman and Director of the Institute of Neurology, Shanghai Medical University and Chairman of the Chinese Association of Neurology. His research interests include experimental ischemia, clinical stroke and cognition.

    Stroke in Chinese represents a first step toward a growing dialogue in an increasingly coordinated effort to prevent and treat stroke in the country where it has the greatest impact.

    Key Words: stroke

    Accession Number: 00007670-200606000-00001
     
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  3. منير الشيخ

    منير الشيخ قلم فضي

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    ORIGINAL RESEARCH COMMUNICATION

    Effect of prenatal food supplementation on birth weight: an observational study from Bangladesh 1,2,3
    Rubina Shaheen, Andres de Francisco, Shams El Arifeen, Eva-Charlotte Ekström and Lars Åke Persson
    1 From the ICDDR,B: Centre for Health and Population Research, Dhaka, Bangladesh (RS and SEA); the Department of Epidemiology, Umeå International School of Public Health, Umeå University, Umeå, Sweden (RS); the Global Forum for Health Research, Geneva, Switzerland (AdF); and International Maternal and Child Health, Uppsala University, Uppsala, Sweden (E-CE and LAP)

    2 Supported by the Bangladesh Integrated Nutrition Project.

    3 Address reprint requests to R Shaheen, Reproductive Health Unit, Public Health Sciences Division, ICDDR,B: Centre for Health and Population Research, Bangladesh, GPO Box 128, Dhaka 1000, Bangladesh. E-mail: rubina.shaheen@epiph.umu.se and rubina@icddrb.org.



    ABSTRACT
    TOP
    ABSTRACT
    INTRODUCTION
    SUBJECTS AND METHODS
    RESULTS
    DISCUSSION
    REFERENCES


    Background: National nutrition programs in Bangladesh have included prenatal food supplementation to reduce maternal and child malnutrition. The knowledge base is weak regarding the effect of prenatal food supplementation on the birth weight (BW) of infants in populations in whom low BW is prevalent and regarding any variation in effect based on maternal nutritional status.

    Objective: We examined whether observational data support an effect of daily prenatal food supplementation on BW by considering the duration of supplementation and whether the effect is modified by maternal postpartum weight (a proxy of prepregnancy weight) groups.

    Design: A cohort of undernourished pregnant women (n = 777) who received prenatal food supplementation (608 kcal/d) was followed. The association between the uptake of food supplements and BW was analyzed after adjustment for potential confounders (n = 619 with complete information). Differential effects in lower and higher maternal postpartum weight groups were examined.

    Results: The average BW was 2521 g. On average, the women received daily supplements for 4 mo, which resulted in an increase in BW of 118 g (1.0 g/d). The strongest effect was found for births occurring in January and February. There was a linear dose-response relation between duration of supplementation and BW for women with higher postpartum weights (42 kg, above the median). In women with lower weights (<42 kg, below median), a shorter duration of supplementation (<4 mo) had no such dose-response relation with BW, but there was a linear dose-response relation for longer durations of supplementation.

    Conclusions: The association between duration of prenatal food supplementation and BW varies with maternal postpartum weight. A large effect was observed after the season with food insecurity (mid-August to mid-November).


    Key Words: Food supplementation • pregnancy • birth weight • maternal weight • season • Bangladesh


    INTRODUCTION
    TOP
    ABSTRACT
    INTRODUCTION
    SUBJECTS AND METHODS
    RESULTS
    DISCUSSION
    REFERENCES


    Low birth weight (LBW), ie, BW < 2500 g, is a global public health concern (1). The problem is most prominent in South Asia, where one-half of the world's LBW babies are born (2). LBW is a reflection of intrauterine growth restriction and of a high frequency of preterm delivery (3). LBW results in a high occurrence of child morbidity (4), impaired development (5-8), and mortality (9).

    Prenatal food supplementation has been used as one of the strategies to improve fetal development in societies where food insecurity, maternal malnutrition, and LBW are prevalent (10-15) as well as in the poor segment of affluent societies (16). Such interventions have reportedly had mixed results (10-19), although due consideration should be given to variations in the amount and composition of supplements, maternal nutrition status, seasonal variation in food security, and other factors that may influence the effect on fetal growth and maternal nutritional status (20). Thus, the knowledge base is still weak regarding the effectiveness of such interventions.

    It has been suggested (21), and later supported by empirical data (22), that the effect of food supplementation is partitioned between the mother and the fetus, depending on the nutritional status of the mother, which may be best represented by her prepregnancy weight. Interestingly, the positive effect of food supplementation on fetal growth is suggested to be lower in most malnourished mothers and larger in mothers with moderate malnutrition (22).

    Mean BW frequently varies with season (23-26), which reflects variations in household food security and maternal weight over the year (23). Consequently, the effect of prenatal food supplements on BW may vary with season. In the Gambia the effect of food supplements on BW was higher after the season characterized by food insecurity, ie, June to October (11, 12, 14).

    The Bangladesh Integrated Nutrition Project (BINP) was initiated with the long-term goal of improving nutritional status so that malnutrition would cease to be a public health problem (27). As a part of this initiative, BINP and its successor—the National Nutrition Project (NNP)—have offered a comprehensive health and nutrition program to pregnant and lactating women and children aged <2 y, including prenatal food supplementation to women with a body mass index (BMI; in kg/m2) < 18.5. Benefiting from this ongoing program, we followed a cohort of 777 pregnant women and examined whether observational data support an effect on BW of a daily prenatal food supplement (608 kcal) that increases the total dose by increasing the number of days of supplementation and is modified by maternal postpartum weight.


    SUBJECTS AND METHODS
    TOP
    ABSTRACT
    INTRODUCTION
    SUBJECTS AND METHODS
    RESULTS
    DISCUSSION
    REFERENCES


    Study site and subjects
    The study was conducted in Shaharasti, one of 7 upazilas (subdistricts) in the Chandpur district, Bangladesh. Shaharasti is located adjacent to a river that annually causes moderate to severe flooding in the surrounding area. The main occupation in the area is agriculture, and the main crops are rice, wheat, potatoes, and sugarcane.

    The BINP initiated its nutrition-related activities in Shaharasti, including food supplementation during pregnancy, in 1996. Four of 9 unions (administrative units in each subdistrict, each with a population of 20 000) in the subdistrict were randomly selected for this study.

    The BINP activities were performed at Community Nutrition Centers (CNCs; 52 in the study area) operated by Community Nutrition Promoters, who were women with children and a minimum of about 8 y of schooling. The centers were located in the villagers' houses, and the program activities were run during the morning from Saturday through Thursday. Each CNC covered 1200 persons, and the promoter made regular household visits to identify pregnant women and invite them to participate in the activities. Pregnant women with a BMI < 18.5 were eligible to participate. Usually, Community Nutrition Promoters invited the women to participate in the food supplementation program early in pregnancy. Participating women were invited to visit the CNC 6 d/wk and received health and nutrition education, food supplementation, and iron-folate supplementation (provided monthly, 2 tablets/d; each tablet containing 60 mg Fe and 250 µg folic acid) according to national recommendations. Compliance with the iron-folate supplementation was not monitored.

    The preparatory field activities of the study started in November 1998, and BW was measured from December 1998 to October 1999. In 1998 there was a severe flood throughout Bangladesh; the flooding in Shaharasti was excessive through October 1998. BINP activities in the field were stopped during peak flooding and restarted in mid-November 1998. Women participating in the BINP program with calculated probable births (based on last menstrual period) between December 1998 and October 1999 were invited to take part in this study (n = 777; Figure 1). The fieldworkers regularly visited the 52 CNCs to identify new enrollees. The Ethical Review Committee of ICDDR,B approved the study. Informed written consent was obtained from each participant.





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    FIGURE 1. Study participation.




    Food supplementation
    Village women employed by the program prepared the food supplements using local products. The prepared food was provided in plastic packets to be mixed with water. The daily supplement contained 80 g roasted rice powder, 40 g roasted pulse powder, 20 g molasses, and 12 mL (6 g) soybean oil, which provided 608 kcal and 17.9 g vegetable protein (11.5% of total energy). The supplements were usually eaten at the CNC, but were often brought to the participants' homes for consumption in the third trimester.
    Measurements
    Information on participation in the food supplementation program was retrospectively collected by the fieldworkers, who conducted 3 structured interviews at the participants' homes. The respondents were requested to report how many days they had consumed the supplement. Different important events in the preceding months were used to improve recall. Additional questions were asked to resolve any missing information on supplement intakes. Information on general dietary intakes was not collected.

    Standard procedures were followed for anthropometric measurements, and the training of fieldworkers included standardization of measurements (28). The women's weights were measured after birth with a precision of 100 g (model 770; SECA, Hamburg, Germany), and length was measured by using a portable scale with a precision of 1 mm. Ninety-seven percent of the analyzed maternal postpartum weights were assessed within 7 d after birth, at the same time as BWs were measured. A notification system was established for births. Efforts were made to measure BW as soon as possible, preferably within 72 h; 23% were measured within 24 h and 85% within 72 h. BW was measured by using a SECA beam scale (model 725) with a precision of 10 g. BWs measured later than 24 h after delivery, but within 7 d of delivery, were transformed to SD scores by using the distribution in this material as standard. The SD scores obtained were transformed back to the corresponding BWs.

    Gestational age at birth was determined on the basis of the date of the last menstrual period. A local calendar sharing Bangla, Arabic, and Gregorian months and dates in parallel and special religious events was used to ensure the accuracy of the dates. Information on maternal age, parity, work (working hours per day), education, and household income was collected in the first interview.

    Analyses
    Participation in the supplementation program was analyzed by including characteristics of women with and without complete data on days of supplementation, BW, and maternal postpartum weight. Descriptive information on distribution of days of supplementation and BW was presented, and differences in mean values by season of birth were analyzed by analysis of variance with an F test. Associations between these 2 variables were analyzed by linear regression, and stratification for season was done. The main goal was to determine possible dose-response relations between days of supplementation and BW and to determine whether any dose-response relations varied by maternal weight, in this case by postpartum weight. BW was plotted as a function of days of supplementation, and lowess moving average lines (29) were fitted for higher and lower maternal postpartum weight groups (postpartum weight median value <42 = 1, 42 = 0). This was followed by multivariate linear regression analyses based on the observations made on the lowess curves, and statistical analysis was done to test the dose-response relation between days of supplementation and BW. Adjustments were made for potential confounding of the dose-response relation. Potential confounding was considered for any cofactor with a P value < 0.20 for any linear or nonlinear association with BW and total days of supplementation. Confounding by the measured variable was excluded if its influence on the effect estimate was <10%. Analyses were done by using the STATISTICAL PACKAGE FOR SOCIAL SCIENCE (version 12.01; SPSS Inc, Chicago).


    RESULTS
    TOP
    ABSTRACT
    INTRODUCTION
    SUBJECTS AND METHODS
    RESULTS
    DISCUSSION
    REFERENCES


    Participation
    Of 777 women in the supplementation program, 619 with complete information on supplementation during pregnancy, BW, postpartum maternal weight, and gestational age at birth were included in the analysis. No differences in maternal, infant, or socioeconomic characteristics were found between those with or without complete data, except for some differences in maternal height (women with complete data were slightly taller), month or season of birth (women with complete data were better represented in the period from December to February), and days of supplementation (women with complete data had slightly shorter periods of supplementation) (Table 1).




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    TABLE 1 Characteristics of the participants with complete and incomplete information on days of supplementation, infant birth weight, postpartum maternal weight, and gestational age at birth1




    Supplementation
    On average, the women started to receive food supplementation at week 15, and the mean (±SD) number of days of food supplement intake was 116 ± 40. Provided that the whole daily supplement was consumed (intake not supervised), the average intake was 70 000 kcal. Compliance with supplementation varied considerably over the year; the lowest values were for those born between January and February (83 d). For 201 (32%) of 619 women, the measurements for supplement intake were based on 3 interviews (2 during pregnancy and one after childbirth); for 173 (28%) of 619 women, the measurements were based on 2 interviews (1 during pregnancy and 1 after childbirth); and for 245 (40%) of 619 women, the measurements were based on 1 interview after childbirth. The number of interviews did not vary by maternal postpartum weight group (< 42 and 42 kg; P = 0.60).
    Birth weight
    Mean (±SD) BW was 2521 ± 382 g, and 48% of the infants had a low BW (<2500 g). The boys had a mean (±SD) BW of 2556 ± 399 g, and the girls had a mean (±SD) BW of 2486 ± 358 g. There was a marked seasonal variation in BW; the lowest mean (±SD) weights were in the period from January to February (2424 ± 397 g), and the highest weights were in the period from March to October (2550 ± 373 g) (P = 0.001).

    Dose-response analyses
    Overall, a longer supplementation period was associated with a higher BW (Figure 2). For each day of supplementation, BW increased by 1.0 g/d (adjusted for gestational age at birth; P = 0.007). The subset of women who gave birth during January and February had an increase in BW of 2.2 g/d of supplementation (n = 140; adjusted for gestational age; P = 0.053).





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    FIGURE 2. Duration of prenatal food supplementation plotted against infant birth weight. Lowess curves for higher (42 kg, above median) and lower (<42 kg, below median) maternal postpartum weight groups are shown. For total duration of supplementation <120 d, there was an interaction between duration of supplementation and maternal postpartum weight group (P = 0.059); for total duration of supplementation above the median, the lines are parallel when assessed by multiple regression analyses.




    The lowess curve from a scatter plot of days of supplementation and BW showed a clear dose-response relation (Figure 2). This was also the case for the subset of women with a postpartum weight above the median (42 kg). Women with a postpartum weight below the median (<42 kg) showed no effect of daily food supplementation on BW unless it was continued beyond 4 mo.
    In a regression analysis based on the pattern of effects visualized in Figure 2, we first considered supplementation up to 120 d and the effects on BW in women with higher and lower postpartum weights (Table 2). Potential confounders were evaluated according to the analysis plan. Women with higher postpartum weights (42 kg) had an increase in BW of 3 g/d of supplementation, whereas no positive effect on BW was observed in the women with lower postpartum weights. For a longer duration of supplementation (>4 mo), women in both postpartum weight groups showed a dose-response relation of an increase in BW of 1.8 g/d of supplementation. Women with a lower postpartum weight, however, had a linear dose-response relation in parallel with but 113 g lower than the other group.




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    TABLE 2 Dose-response analyses for subgroups defined by duration of prenatal food supplementation: outcome variable is birth weight (g)1





    DISCUSSION
    TOP
    ABSTRACT
    INTRODUCTION
    SUBJECTS AND METHODS
    RESULTS
    DISCUSSION
    REFERENCES


    On the basis of this observational study of pregnant women participating in a food supplementation program in Bangladesh, there was an overall dose-response relation of daily food supplementation (608 kcal) that resulted in an increase in BW of 1 g/d, which varied considerably by postpartum weight. BW was least affected in the most malnourished women. Greater effects were found for births during January and February after a period of food insecurity in the community.
    Data were collected prospectively by trained fieldworkers. Information on compliance with the supplementation regimen was obtained by repeated dietary recalls, including logical controls of information by questioning about missing information and by using a local calendar of events. Anthropometric information was collected after proper training, standardization of instruments, and retraining over the study period. Most BWs were measured within 72 h of childbirth. Efforts were made to obtain the accurate date of the last menstrual period, including the use of different calendars and a list of local events.

    The issue of reverse causality, ie, that women who had longer pregnancies had the chance to consume the supplement for a longer time, was addressed by adjusting the multivariate analyses by gestational age at birth.

    The external validity of the demonstrated effect size was limited; we showed that factors such as maternal nutritional status and season (most likely a proxy of food security) influenced the size of the effect. Thus, the program may have another effect in a different setting or in another year in the same geographic area. However, the finding of differential effects in women on the basis of postpartum weight is most likely to be shown in other settings and other seasons.

    The average effect of supplementation (70 000 kcal; no supervised intake) was an increase in BW of 118 g. This effect is comparable with the 136-g overall improvement in BW observed in a study in the Gambia (14) and with the 100-g improvement in BW observed in a study in East Java (13). The average effect found in our study is somewhat lower than the estimates calculated by Lechtig et al (10) a few decades ago: an increase in BW of 25–85 g/10 000 kcal of a balanced supplementation. The lower effect may have been because the actual consumption was lower than the average of 70 000 kcal. Nevertheless, the overall effect obtained in this study was reasonably large, which has potentially significant positive consequences for child health.

    Several explanations are possible for the results found in this study. First, for the effect of food supplementation on BW to be visible, the distribution of risk in terms of giving birth to LBW babies and responsiveness in terms of the potential for improvement in BW was favorable in the study population, ie, maternal weight was low, there were enough women who were considered marginally malnourished in the local context, and food was insecure in the study area. Second, the food supplement offered by the BINP was a low-protein, high-calorie food that was found to be more effective at improving BW than were the alternatives (17-19). Third, compared with women in different trials, the women in this observational study had the opportunity to start the supplement early in pregnancy, which increased their total dose.

    Recently, the effect of the BINP on childhood underweight has been questioned (30). The authors based their conclusions on an ecologic analysis of prevalence of underweight in intervention and nonintervention areas. Such a crude design does not provide a satisfactory basis for judging the effectiveness of the program. Our data on individual supplementation and BW indicated a substantial effect on BW, although it varied with maternal nutritional status and season.

    The results also need to be discussed in the context of BINP performance, as reported by the World Bank (31). The report suggests that the program might have been more successful if it had restricted its attention to the most malnourished women, improved targeting to reduce type II error, and tried harder to discourage leakage and substitution. Although we were unable to answer questions related to leakage (ie, whether the supplements intended for the study subjects were shared with others) and substitution (whether the supplement replaced usual dietary intake), our results suggest that targeting based on a BMI < 18.5 results in a detectable positive effect of supplementation on BW when the biological plausibility of such an effect is likely. However, contrary to the report, we showed that a positive effect is possible in relatively well-nourished women who are marginally malnourished in the local context but who may be considered severely malnourished in the global context; in most malnourished women, no such effects occur. Our results support the seasonal effects presented in the BINP report.

    Our study provides evidence for relatively large effects at the beginning of the year—an improvement in BW of 183 g after an average of 83 d of supplementation. The usual period of relative food insecurity in Bangladesh is from mid-August to mid-November, ie, 2–5 mo before births in January and February (32-34). Flooding usually occurs in August–September, but during the study year flooding was excessive and of a longer duration. The relatively large effect of supplementation may have been related to the excessive flooding during the months before the study onset and to the pronounced food insecurity that followed.

    The association between days of supplementation and BW varied by maternal postpartum weight group. This finding may have different explanations. Prenatal food supplements consumed by underweight women are partitioned to both the mother and fetus. Winkvist et al (22) have suggested that both mother and fetus may benefit from a supplement. Maternal prepregnancy weight and the dose of the supplement determine the size and partitioning of the effect that preferably should be evaluated over an entire pregnancy cycle (21, 22, 35). Our study lacked information on maternal weight change and was limited to the period from pregnancy to childbirth. The differential effect on BW by lower and higher maternal postpartum weight groups may fit with the principles suggested by Winkvist et al (22). Ideally, we should have had used prepregnancy or early pregnancy weights in the analysis. However, we used maternal postpartum weight as a dichotomous stratification variable with an arbitrary division into 2 groups. Any misclassification into lower and higher maternal weight groups that may have happened through differential pregnancy net weight gains probably had no major influence on the results.

    Eligibility for prenatal food supplementation in Bangladesh is limited to women with a BMI < 18.5. This arbitrary criterion should be reexamined because women with a BMI approaching 18.5 in this study had a clear positive effect of food supplementation.

    To conclude, we have shown an association between prenatal food supplementation and BW that varied with maternal weight and season. The relatively large effect observed occurred mainly after a period of food insecurity in the study area. These findings may be important in determining which population groups should be targeted for prenatal food supplementation programs. It is possible that malnutrition will cease to be a major public health problem because improvements in BW have positive effects across generations, ie, female newborns with higher BWs will become well-nourished women who later give birth to infants with higher BWs. There is a need to understand the effect of prenatal food supplementation on perinatal mortality because evidence of the direct effect of prenatal food supplementation on mortality is still limited in the context that the relation between size at birth and infant mortality is primarily due to the close relation between birth weight and gestational age at birth.



    ACKNOWLEDGMENTS

    ICDDR,B acknowledges with gratitude the commitment of BINP to the Centre's research efforts. We thank Zeba Mahmud (BRAC) and Saskia Osendarp, Ruksana Haider, George J Fuchs, and SK Roy (ICDDR,B) for supporting us in various ways in completing this research project.

    RS contributed to all stages of the study, including the data analysis, and developed the first draft of the manuscript. AdF contributed to the planning phase and the writing of the manuscript. SEA, E-CE, and L&Aring;P contributed to the data analysis and the writing of the manuscript. All authors read different versions of the manuscript and agreed to the final version. None of the authors had a conflict of interest.


    REFERENCES
    TOP
    ABSTRACT
    INTRODUCTION
    SUBJECTS AND METHODS
    RESULTS
    DISCUSSION
    REFERENCES




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    Received for publication December 26, 2005. Accepted for publication February 10, 2006.
     
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  5. منير الشيخ

    منير الشيخ قلم فضي

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    ORIGINAL RESEARCH COMMUNICATION

    Effect of n–3 long-chain polyunsaturated fatty acid supplementation of women with low-risk pregnancies on pregnancy outcomes and growth measures at birth: a meta-analysis of randomized controlled trials 1,2
    Hania Szajewska, Andrea Horvath and Berthold Koletzko
    1 From the Department of Paediatric Gastroenterology and Nutrition, The Medical University of Warsaw, Warsaw, Poland (HS and AH), and Dr von Hauner Children's Hospital, Ludwig Maximilians University of Munich, Munich, Germany (BK)

    2 Reprints not available. Address correspondence to H Szajewska, Department of Paediatric Gastroenterology and Nutrition, The Medical University of Warsaw, Dzialdowska 1, 01-184 Warsaw, Poland. E-mail: hania@ipgate.pl.



    ABSTRACT
    TOP
    ABSTRACT
    INTRODUCTION
    MATERIALS AND METHODS
    RESULTS
    REFERENCES


    Background: It is hypothesized that the intake of long-chain polyunsaturated fatty acids (LC-PUFAs) throughout pregnancy is important to maternal health and fetal and infant development.

    Objective: The objective was to evaluate systematically the effect of LC-PUFA supplementation of pregnant women's diets on pregnancy outcomes and growth measures at birth.

    Design: We searched MEDLINE, EMBASE, CINAHL, and the Cochrane Library through August 2005 and also searched the references in reviewed articles for randomized controlled trials (RCTs) comparing LC-PUFA supplementation with placebo or no supplementation.

    Results: Of 6 included RCTs, only 1 was judged to be at low risk of bias. Supplementation with n–3 LC-PUFAs in these 6 RCTs (1278 infants) was associated with a significantly greater length of pregnancy [weighted mean difference (WMD): 1.57 d; 95% CI: 0.35, 2.78 d; findings stable on sensitivity analysis] than in control subjects. We found no evidence that supplementation influenced the percentage of preterm deliveries, the rate of low-birth-weight infants, or the rate of preeclampsia or eclampsia. We found no significant difference in the 6 RCTs (1278 infants) in birth weight (WMD: 54 g; 95% CI: –3.1, 111 g) and no significant difference in 5 RCTs (1262 infants) in birth length (WMD: 0.23 cm; 95% CI: –0.04, 0.5 cm), but, in 4 RCTs (729 infants), there was a significant increase in head circumference (WMD: 0.26 cm; 95% CI: 0.02, 0.49 cm; significance was lost on sensitivity analysis).

    Conclusions: n–3 LC-PUFA supplementation during pregnancy may enhance pregnancy duration and head circumference, but the mean effect size is small. The implications of these findings for later growth and development remain to be elucidated.


    Key Words: Nutrition • feeding • development • long-chain polyunsaturated fatty acids • supplementation • pregnancy


    INTRODUCTION
    TOP
    ABSTRACT
    INTRODUCTION
    MATERIALS AND METHODS
    RESULTS
    REFERENCES


    Two long-chain polyunsaturated fatty acids (LC-PUFAs)—docosahexaenoic acid (DHA, 22:6n–3) and arachidonic acid (AA, 20:4n–6)—are important to fetal and infant growth and development. In the cerebral cortex and retina, DHA constitutes a large percentage of the phospholipid fatty acids [(FAs) 1, 2]; AA, which is also essential for normal growth and development (3), is the precursor of eicosanoids (4, 5). These FAs, which are essential components of membrane phospholipids, are deposited in relatively large amounts in the central nervous system during brain growth. Deposition is especially high during the last trimester of pregnancy and first months of life (6, 7), when an insufficient amount can lead to adverse effects or irreversible damage (8, 9).

    DHA and AA are members of the n–3 and n–6 families of FAs, respectively. Because humans do not possess desaturase enzymes that are capable of inserting either the n–3 or the n–6 double bonds, both can be derived only from the diet and thus are regarded as essential. DHA may be obtained directly from dietary fish oils or from the precursor -linolenic acid (18:3n–3); the usual precursor of AA is dietary linoleic acid (18:2n–6) from plant sources. When fish oil is provided in the diet, eicosapentaenoic acid (EPA, 20:5n–3) will be supplied, as well as DHA.

    Both n–3 and n–6 FAs required for the fetus are supplied to the fetus during pregnancy by preferential placental transfer (5, 10, 11, 12). Although both precursor essential FAs and preformed LC-PUFAs can be transported, there is a preferential transfer of the latter form (5). The fetus and newborn infant depend, therefore, on a maternal supply of DHA and AA. It has been proposed that an additional supply of LC-PUFAs, particularly DHA, during pregnancy or lactation or both would improve an infant's later cognitive and visual development (13, 14). It has also been suggested that a greater intake of LC-PUFAs, particularly that of DHA and EPA obtained from fish and fish oils, may have a beneficial effect on pregnancy outcomes (15).

    Several studies, many of them observational, have assessed the effect of LC-PUFA supplementation of the diet of pregnant women on pregnancy outcomes. Most studies undertaken had the aim of improving pregnancy outcomes—ie, preventing preeclampsia, prolonging gestation, preventing preterm birth, and improving fetal growth (15, 16). The rationale for the supplementation was to modify the balance of production of prostaglandins involved in the initiation of labor, and thus these studies exclusively used n–3 LC-PUFAs, precursors of the 3 and 5 series eicosanoids (15, 16). However, no firm dietary recommendations can be based on the available evidence (17).

    In this study, we sought to explore the potential beneficial effects of supplementation of pregnant women with LC-PUFAs on pregnancy outcomes and fetal growth by conducting a systematic review and meta-analysis of randomized controlled trials (RCTs).


    MATERIALS AND METHODS
    TOP
    ABSTRACT
    INTRODUCTION
    MATERIALS AND METHODS
    RESULTS
    REFERENCES


    Criteria for inclusion of studies
    Studies included in this review had to be RCTs or quasi-RCTs comparing LC-PUFA supplementation with placebo or no supplementation in healthy pregnant women. After an initial assessment of the included trials, we decided to focus our attention on pregnancy outcomes and growth measures at birth. In addition, we extracted any data related to adverse events. Trials in women with high-risk pregnancies were not included. A high-risk pregnancy was defined as one in which a condition places the mother, the developing fetus, or both at higher-than-normal risk for complications during or after the pregnancy and birth (eg, a preterm delivery during an earlier pregnancy, intrauterine growth retardation, pregnancy-induced hypertension, or multiparity). Trials in which precursor essential FAs (-linolenic and linoleic acids) were used in the intervention group were not included, because intake of the precursors is far less effective with respect to LC-PUFA deposition in fetal brain. Trials with only biochemical outcomes were not included.

    Search strategy to identify studies
    The search strategy included the use of a validated filter for identifying RCTs (18), which was combined with a topic-specific strategy using PubMed's MeSH terms—eg, FA or omega or n–6 or n–3 or eicosapentaenoic acid or EPA or docosahexaenoic acid or DHA or arachidonic acid or LC-PUFA or long-chain FA or essential FA or fish oil. The full search strategy is available from the authors on request.

    We performed a computerized literature search of MEDLINE (from 1966 to August 2005), EMBASE (from 1980 to August 2005), the Cumulative Index to Nursing and Allied Health (CINALH) (from 1982 to August 2005), and the Cochrane Library (issue 2, 2005). We supplemented this search by examining published reviews and position papers. Additional sources were references in reviewed articles. We imposed no limit with respect to the language of publication, but certain publication types (ie, letters to the editor, abstracts, and proceedings from scientific meetings) were excluded.

    Methods of the review
    Trial selection
    One of us (AH) initially screened the title, abstract, and key words of every report identified by the search strategy; this reviewer then retrieved the full text for potentially relevant trials and for reports whose relevance was not clear. Two of us (HS and AH) independently applied the inclusion criteria to each potentially relevant trial to ascertain its eligibility. If differences in opinion existed, they were resolved by discussion.

    Quality assessment of trials
    Two of us (AH and HS) independently, but without being blinded to the authors or journal, assessed the quality of the studies that met the inclusion criteria. We assessed the use of the following strategies associated with good-quality studies: generation of allocation sequences and allocation concealment; blinding of investigators, participants, outcome assessors, and data analysts (yes, no, or not reported); intention-to-treat analysis (yes or no); and comprehensive follow-up. The generation of allocation sequences was considered adequate if the resulting sequences were unpredictable (eg, computer-generated random numbers) and inadequate if the resulting sequences were predictable (eg, according to case record number). Allocation concealment was considered adequate when the randomization method used did not allow the investigator or the participant to identify or influence the intervention group before enrollment of eligible participants in the study. The quality of the allocation concealment was considered unclear when randomization was used but no information about the method was available and considered inadequate when inappropriate methods of randomization were used.

    Methods for blinding were considered double-blind (neither patients nor care providers or assessors knew which treatment was given), single-blind (either patients or care providers or assessors were aware of treatment), and open (all parties were aware of treatment). With respect to an intention-to-treat analysis, a positive finding on the reviewers' part meant that the authors had specifically reported undertaking this type of analysis or that our own study confirmed this finding or both. Conversely, a negative finding meant that authors did not report the use of intention-to-treat analysis, that we could not confirm its use on study assessment, or both. To evaluate the completeness of patient follow-up, we ascertained the percentage of participants excluded or lost to follow-up. Completeness of follow-up was considered to be adequate if 80% of participants were included in the final analysis and assumed to be adequate when there was no mention of losses to follow-up. We defined the categories of risk of bias by the number of criteria judged inadequate in each study: low risk of bias (1 inadequate criterion), medium risk of bias (3 inadequate criteria), and high risk of bias (> 3 inadequate criteria).

    Data extraction
    Two of us (AH and HS) independently performed data extraction by using standard data-extraction forms. When important data were not reported or were unclear, as in the case of studies by Smuts et al (19, 20), we contacted the corresponding authors of the primary studies for clarification. Discrepancies between reviewers were resolved by discussion. For dichotomous outcomes, we extracted the total number of participants and the number of participants who experienced the event. For continuous outcomes, we extracted the total number of participants and the means and SDs. In one RCT (21), participants were randomly assigned to 3 groups: an intervention group that received fish oil, a control group that received olive oil, and another control group that received no oil supplementation. Because the objective of our review was to compare supplementation with placebo or no supplementation, we combined both control arms into a single control group according to the method of Hogg and Craig (22). We compared the extracted data to identify errors. One reviewer (HS) entered the data into REVIEW MANAGER for WINDOWS software (REVMAN version 4.2; The Cochrane Collaboration, Oxford, United Kingdom) for analysis.

    Statistical analysis
    We used the REVMAN software for all statistical analyses. The weighted mean difference (WMD) between the treatment and control groups was selected to represent the difference in continuous outcomes with 95% CIs. The dichotomous outcomes for individual studies and pooled statistics are reported as the risk ratio (RR) between the experimental and control groups (with 95% CI). To pool the data, we used either a fixed effect or random effects model approach, according to the heterogeneity in outcomes across studies; this was analyzed by using Cochrane's Q statistic with = 0.05 for statistical significance and by using the statistic I2, which is derived from Q and which describes the proportion of total variation that is due to heterogeneity beyond chance. Sensitivity analyses assessed the robustness of results after removal of studies that were judged to have a high risk of bias. To test for publication bias, we used a test for asymmetry of the funnel plot proposed by Egger et al (23). This test detects funnel plot asymmetry by ascertaining whether the intercept deviates significantly from zero in a regression of the normalized effect estimate (estimate divided by its SE) against precision (reciprocal of the SEE) weighted by the reciprocal of the variance of the estimate, as ascertained with the use of STATSDIRECT software (version 2.3.8; StatsDirect Ltd, Sale, United Kingdom).

    Description of studies
    We initially identified 21 articles. The characteristics of the included trials are summarized in Table 1. Six RCTs (14, 19, 20, 21, 24, 25), with 1278 participants, met our defined inclusion criteria. All were fully peer-reviewed publications. When studies had groups assigned both randomly and nonrandomly, the nonrandomized arm was not considered further in this review. Investigators in one trial (14) reported supplementation during pregnancy and lactation, but we included in this review only that data related to supplementation during pregnancy. Investigators in other trials reported supplementation with either DHA alone (18, 19) or in combination with eicosapentaenoic acid (EPA; 14, 21, 24, 25) in healthy pregnant women. The duration and the sources and amounts of n–3 LC-PUFA, DHA, and EPA supplied varied between trials. The highest doses—1183 mg DHA and 803 mg EPA/d and 920 mg DHA and 1280 mg EPA/d—were used in the studies by Helland et al (14) and Olsen et al (21), respectively. In the remaining studies, the dose of DHA was 150–200 mg/d. On the basis of the dose of supplementation, studies could be divided into 2 groups: a group with higher—1000 mg/d—(14, 21) and a group with lower—200 mg/d—(19, 20, 24, 25) DHA intake. The trials differed in the starting time of intervention, beginning as early as week 15 of gestation (24) or as late as week 30 of gestation (21). Trials with all LC-PUFA (n–3 and n–6) supplementation were considered for this review. However, none of the trials used n–6 supplementation in the intervention group. Thus, the remainder of this review applies only to n–3 LC-PUFA supplementation.




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    TABLE 1 Characteristics of included trials1




    The characteristics of the excluded trials, including the reasons for exclusion, are summarized in Table 2. In brief, trials were excluded because they were not RCTs, the population was the same as reported in another study, or only biochemical data were reported. They also were excluded if there was no report of any of our defined outcomes, if they were abstracts of subsequently published randomized controlled trials, or if they were duplicate publications.



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    TABLE 2 Characteristics of the excluded studies




    The quality of methods of the included studies
    The results of the quality assessment of the methods of included studies are shown in Table 1. We assessed the risk of bias as low in only one trial (21). Only 2 trials (21, 25) used an adequate method to conceal allocation. The method used in the remaining 4 trials (14, 19, 20, 24) was unclear. Five trials (14, 19, 20, 21, 24) were described as "double-blinded", and 1 trial (25) was open. An adequate description of the intention-to-treat analysis was provided in only one RCT (21). Withdrawals and dropouts were described adequately in all studies. Three trials (20, 21, 25) included an adequate proportion (ie, 80%) of participants in the final analysis, and 3 trials (14, 19, 24) included an inadequate proportion.

    RESULTS
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    ABSTRACT
    INTRODUCTION
    MATERIALS AND METHODS
    RESULTS
    REFERENCES


    Duration of pregnancy
    n–3 Supplementation was associated, as compared with no supplementation in control subjects, with significantly greater duration of pregnancy (WMD = 1.57 d; 95% CI: 0.35, 2.78 d) in 1278 participants of 6 RCTs (14, 19, 20, 21, 24, 25; Figure 1). There was no heterogeneity (chi-square = 5.61, P = 0.35, I2 = 10.8%), and significance was stable on sensitivity analysis (WMD: 1.59 d; 95% CI: 0.31, 2.87 d).





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    FIGURE 1. Weighted mean difference (WMD) and 95% CI of the duration of pregnancy in women supplemented with n–3 long-chain polyunsaturated fatty acid as compared with women who received no supplementation or placebo. Values for individual trials and pooled data (fixed-effect model) are shown.




    Other pregnancy outcomes
    We found no significant difference between supplemented and nonsupplemented subjects in the percentage of preterm deliveries (ie, < 37 wk gestation; RR = 0.67; 95% CI: 0.41, 1.10) of 861 infants from 3 RCTs (19, 20, 21) or in the rate of low birth weight (ie, < 2500 g; RR = 0.66; 95% CI: 0.34, 0.26) in 328 infants from 2 RCTs (19, 20). There was no significant difference between supplemented and nonsupplemented subjects in the rate of preeclampsia or eclampsia (RR = 0.73; 95% CI: 0.22, 2.37) in 328 women from 2 RCTs (19, 20) or in the rate of cesarean delivery (RR = 1.17 (95% CI: 0.79, 1.74) in those women and in 669 women from 3 RCTs (14, 19, 20). In addition, there was no significant difference between supplemented and nonsupplemented subjects in the rate of gestational diabetes (RR = 0.73; 95% CI: 0.22, 2.37) in 328 women from 2 RCTs (19, 20). In 4 RCTs (14, 19, 20, 25) involving 685 participants, no significant difference between supplemented and nonsupplemented subjects was found in the placental weight (WMD: 10.9 g; 95% CI: –10.4, 32.2 d). For all studied outcomes, there was no significant heterogeneity between the studies, and findings were stable on sensitivity analyses.
    Growth measures in newborn infants
    In the 6 RCTs (1278 infants), we found no significant difference in birth weight between supplemented and nonsupplemented control subjects (pooled WMD: 54 g; 95% CI: –3.1, 111 g; Figure 2). There was no heterogeneity (chi-square = 7.69, P = 0.17, I2 = 35%), and this finding was stable on sensitivity analysis (WMD: 59 g; 95% CI: –0.2, 119 g).





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    FIGURE 2. Weighted mean difference (WMD) and 95% CI of the birth weight (in g) of infants born to women who during pregnancy were supplemented with n–3 long-chain polyunsaturated fatty acid as compared with the infants born to women who received no supplementation or placebo. Values for individual trials and pooled data (fixed-effect model) are shown.




    Five RCTs involving 1262 infants showed no significant difference between supplemented and nonsupplemented subjects in the length at birth (pooled WMD: 0.23 cm; 95% CI: –0.04, 0.5 cm; Figure 3). There was no heterogeneity (chi-square = 5.67, P = 0.23, I2 = 29.4%), and again, this finding was stable on sensitivity analysis (WMD 0.26 cm, 95% CI: –0.02, 0.5 cm).




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    FIGURE 3. Weighted mean difference (WMD) and 95% CI of the birth length (in cm) of infants born to women who during pregnancy were supplemented with n–3 long-chain polyunsaturated fatty acid as compared with the infants born to women who received no supplementation or placebo. Values for individual trials and pooled data (fixed-effect model) are shown.




    Supplementation was associated in 4 RCTs (729 infants) with significantly greater head circumference of the infants in the supplemented group, as compared with those of the nonsupplemented control group (pooled WMD: 0.26 cm; 95% CI: 0.02, 0.49 cm; Figure 4). There was no heterogeneity (chi-square = 4.60, P = 0.20, I2 = 34.8%). The significantly greater head circumference of the infants in the supplemented group was lost in sensitivity analysis (WMD: 0.26 cm; 95% CI: –0.02, 0.53 cm).




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    FIGURE 4. Weighted mean difference (WMD) and 95% CI of head circumference (in cm) at birth of infants born to women who during pregnancy were supplemented with n–3 long-chain polyunsaturated fatty acid as compared with that of infants born to women who received placebo or no supplementation. Values for individual trials and pooled data (fixed-effect model) are shown.




    Publication bias
    We found no evidence of publication bias in any of the comparisons of the 6 included trials.
    Adverse events
    A narrative synthesis of the data on adverse events was undertaken. Of the 6 trials included in the review, adverse effects were reported in only 3 (14, 20, 21). Helland et al (14) reported similar rates of withdrawal because of patients who felt discomfort while taking the supplement (43.1% in the cod liver oil group and 38.7% corn oil group). These investigators reported supplementation during both pregnancy and lactation; separate data on the incidence of adverse effects with supplementation during pregnancy were not reported. Olsen et al (21) showed that the proportion of women who reported belching and unpleasant taste attributed to the oil capsules was significantly (P < 0.001) greater in the fish-oil group than in the control groups (70% compared with 20% and 42% compared with 7.4%, respectively). There was a trend regarding blood loss at delivery, which was greatest in the fish-oil group and lowest in the olive-oil group (P = 0.1, analysis of variance); the difference between the fish-oil and olive-oil groups was significant (P = 0.04). There were no significant differences between groups in other possible side effects of the fish oil, such as prolongation of labor or the need for a surgical delivery. In a study in which DHA was consumed from eggs, Smuts et al (20) reported that the proportion of mothers who experienced 1 adverse event was significantly (P < 0.01) higher in the regular egg group than in the supplemented group (38% and 25%, respectively). Serious adverse events occurred in the high-DHA egg group no more often than was expected for the population, and the 2 groups had the same number of total serious adverse events. Consequently, serious adverse events were not clearly linked to DHA supplementation. Neonates born to supplemented and unsupplemented women did not differ significantly in rates of adverse events or serious adverse events.

    DISCUSSION
    The results of this analysis indicate that n–3 LC-PUFA supplementation during pregnancy may increase the duration of pregnancy by an average of 1.6 d. Furthermore, n–3 LC-PUFA supplementation during pregnancy was associated with a trend toward greater growth measures at birth; however, this difference was significant only for head circumference, which was an average of 0.26 cm greater in the supplemented group, but significance was lost on sensitivity analysis.

    These findings are based on the pooled results of included trials. However, only one trial (21) was of high quality with respect to fulfilling all criteria for method quality. In that RCT, supplementation with fish oil was associated with a significantly greater duration of pregnancy (WMD: 2.77 d; 95% CI: 0.8, 5 d) and significantly greater birth weight (WMD: 97 g; 95% CI: 8, 186 g) than were seen in the control subjects. A difference of this magnitude in birth weight appears to be of little of clinical importance for most healthy babies; however, such a shift in the birth-weight distribution of a population may affect the proportion of infants born with a low birth weight, which is associated with greater risks with respect to long-term child health (40, 41). In the 2 RCTs that involved infants with a birth weight < 2500 g (n = 328), there was only a nonsignificant trend toward a reduction in the proportion of low-birth-weight infants with supplementation. Therefore, the question as to whether n–3 LC-PUFA supplementation can affect birth weight deserves further attention in future studies with larger numbers of subjects. n–3 LC-PUFA supplementation during pregnancy had no clear effect on other pregnancy outcomes—including rates of gestational diabetes, preeclampsia or eclampsia, and cesarean delivery—or on placental weight. Whereas no benefit existed for these pregnancy outcomes, neither was there an indication of any safety concerns with respect to the use of n–3 LC-PUFA supplementation to enhance the n–3 PUFA supply to fetal tissues or for other reasons. To minimize bias, we chose to include only RCTs in our review (42). However, it is noteworthy that some observational studies, mainly in populations with high consumption of seafood, have suggested that greater marine n–3 LC-PUFA intake during pregnancy promotes longer gestation and higher birth weight (15, 43, 44); other studies did not confirm these findings (45).

    The conclusions from our review apply only to women whose pregnancies are not high-risk pregnancies. Available results from RCTs involving women at high risk of preterm birth indicate that fish-oil supplementation during pregnancy has a small effect of prolonging gestation; no such effect was observed in women with twin pregnancies (46). There appears to be no benefit of fish-oil supplementation in increasing birth weight or preventing preeclampsia in women with high-risk pregnancies (46). A full-scale systematic review is needed to ascertain the effect of supplementation in that patient population.

    This review focused on the effect of LC-PUFA supplementation during pregnancy on pregnancy outcomes and infant growth measures. Available studies suggest no beneficial or harmful effects on infants' visual function (47) or cognitive development (26) as a result of LC-PUFA supplementation during pregnancy. However, one cannot exclude the possibility that longer supplementation is needed. Results from one RCT showed that the children of women who supplemented their diet with DHA during both pregnancy and lactation scored higher on standardized intelligence and achievements tests (Kaufman Assessment Battery for Children) at 4 y of age than did the children of women who supplemented their diets with FAs that did not contain DHA (26). Because these conclusions are based on limited available evidence, further studies are needed to examine this issue.

    Limitations
    We acknowledge several limitations to this review. The sample sizes in some trials, as well as the number of trials for some comparisons (eg, low-birth-weight infants and preeclampsia or eclampsia), were very small. The pooled sample sizes were also small, and, thus, there was little statistical power; consequently, we cannot exclude chance as an explanation for the results of many comparisons. Marked variability among study populations, baseline n–3 LC-PUFA status, and the interventions tested may have decreased the sensitivity for detecting possible effects. The quality of the methods and the quality of reporting results varied and sometimes were poor. As discussed earlier, potential limitations include unclear or inadequate allocation concealment, no intention-to-treat analysis, and no blinding. The findings are, therefore, likely to be affected to various degrees by selection, attrition, or performance biases (or all). In our meta-analysis, the statistical tests of the homogeneity (total consistency) of the results were nonsignificant. However, it is important to stress that the power of the statistical methods that investigate heterogeneity is limited, particularly for meta-analyses based on a small number of studies, as in this case. Consequently, the results of our meta-analysis, particularly those regarding pregnancy outcomes, should be viewed with caution. Similarly, given the small number of studies, statistical conclusions abouts the publication bias may be flawed.

    Conclusions
    Some evidence exists that maternal LC-PUFA supplementation is associated with a small increment in the duration of pregnancy; however, the implications of this finding for later growth and development are not clear. Further studies that have larger sample sizes and that take confounding factors into account are needed to examine the effects of such supplementation on growth measures and the rates of low birth weight.



    ACKNOWLEDGMENTS

    BK conceptualized this review, and all authors helped write the protocol. AH identified articles for inclusion in the review. HS and AH extracted the data and also assessed study quality. HS assumed the main responsibility for the analysis and for writing of the review, although all authors contributed to (and agreed on) the final version. None of the authors had any personal or financial conflict of interest.


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    ABSTRACT
    INTRODUCTION
    MATERIALS AND METHODS
    RESULTS
    REFERENCES




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    de Groot RH, Hornstra G, van Houwelingen AC, Roumen F. Effect of alpha-linolenic acid supplementation during pregnancy on maternal and neonatal polyunsaturated fatty acid status and pregnancy outcome. Am J Clin Nutr 2004;79:251–60.[Abstract/Free Full Text]
    de Groot RH, Adam J, Jolles J, Hornstra. Alpha-linolenic acid supplementation during human pregnancy does not effect cognitive functioning. Prostaglandins Leukot Essent Fatty Acids 2004;70:41–7.[Medline]
    Haugen G, Helland I. Influence of preeclampsia or maternal intake of omega-3 fatty acids on the vasoactive effect of prostaglandin F-two-alpha in human umbilical arteries. Gynecol Obstet Invest 2001;52:75–81.[Medline]
    Helland IB, Smith L, Saarem K, Saugstad OD, Drevon CA. Maternal supplementation with very-long-chain n–3 fatty acids during pregnancy and lactation augments children's IQ at 4 years of age. Pediatrics 2003;111:e39–44.[Abstract/Free Full Text]
    van Houwelingen AC, Sorensen JD, Hornstra G, et al. Essential fatty acid status in neonates after fish-oil supplementation during late pregnancy. Br J Nutr 1995;74:723–31.[Medline]
    Montgomery C, Speake BK, Cameron A, Sattar N, Weaver LT. Maternal docosahexaenoic acid supplementation and fetal accretion. Br J Nutr 2003;90:135–45.[Medline]
    Olsen SF, Soorensen JD, Sechere NJ, et al. Fish oil supplementation and duration of pregnancy. A randomised controlled trial. Ugeskr Laeger 1994;156:1302–7.
    Otto SJ, van Houwelingen AC, Hornstra G. The effect of supplementation with docosahexaenoic and arachidonic acid derived from single cell oils on plasma and erythrocyte fatty acids of pregnant women in the second trimester. Prostaglandins Leukot Essent Fatty Acids 2000;63:323–8.[Medline]
    Salvig JD, Olsen SF, Secher NJ. Effects of fish oil supplementation in late pregnancy on blood pressure: a randomised controlled trial. Br J Obstet Gynaecol 1996;103:529–33.[Medline]
    Sorensen JD, Olsen SF, Pedersen AK, Boris J, Secher NJ, FitzGerald GA. Effects of fish oil supplementation in the third trimester of pregnancy on prostacyclin and thromboxane production. Am J Obstet Gynecol 1993;168:915–22.[Medline]
    Sorensen JD, Olsen SF, Secher NJ, Jespersen J. Effects of fish oil supplementation in late pregnancy on blood lipids, serum urate, coagulation and fibrinolysis. A randomized controlled study. Fibrinolysis 1994;8:54–60.
    Koletzko B. Early nutrition and its later consequences: new opportunities. Adv Exp Med Biol 2005;569:1–12.[Medline]
    Barker D. Fetal origins of coronary heart disease. Br Med J 1995;171–4.
    Higgins JPT, Green S, eds. Cochrane handbook for systematic reviews of interventions 4.2.4. In: The Cochrane Library. Chichester, United Kingdom: Wiley & Sons, Ltd., 2005.
    Olsen SF, Olsen J, Frische G. Does fish consumption during pregnancy increase fetal growth? A study of the size of the newborn, placental weight and gestational age in relation to fish consumption during pregnancy. Int J Epidemiol 1990;19:971–7.
    Olsen SF, Grandjean P, Weihe P, Videro T. Frequency of seafood intake in pregnancy as a determinant of birth weight: evidence for a dose dependent relationship. J Epidemiol Community Health 1993;47:436–40.[Abstract]
    Oken E, Kleinman KP, Olsen SF, Rich-Edwards JW, Gillman MW. Associations of seafood and elongated n–3 fatty acid intake with fetal growth and length of gestation: results from a US pregnancy cohort. Am J Epidemiol 2004;160:774–83.[Abstract/Free Full Text]
    Olsen SF, Secher NJ, Tabor A, Weber T, Walker JJ, Gluud C. Randomised clinical trials of fish oil supplementation in high risk pregnancies. Fish Oil Trials In Pregnancy (FOTIP) Team. Br J Obstet Gynaecol 2000;107:382–95.
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    Received for publication October 26, 2005. Accepted for publication February 22, 2006.
     
  6.   مشاركة رقم : 4    ‏2006-06-18
  7. منير الشيخ

    منير الشيخ قلم فضي

    التسجيل :
    ‏2002-12-28
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    Fruit and vegetable intakes and bone mineral status: a cross-sectional study in 5 age and *** cohorts1,2,3
    Celia J Prynne, Gita D Mishra, Maria A O'Connell, Graciela Muniz, M Ann Laskey, Liya Yan, Ann Prentice and Fiona Ginty
    1 From the Elsie Widdowson Laboratory, MRC Human Nutrition Research, Cambridge, United Kingdom

    1 From the Elsie Widdowson Laboratory, MRC Human Nutrition Research, Cambridge, United Kingdom.

    2 Supported by Project Award N05044 from the Food Standards Agency.

    3 Reprints not available. Address correspondence to CJ Prynne, Elsie Widdowson Laboratory, MRC Human Nutrition Research, Fulbourn Road, Cambridge, CB1 9NL, United Kingdom. E-mail: celia.greenberg@mrc-hnr.cam.ac.uk.

    See corresponding editorial on page 1254.



    ABSTRACT
    TOP
    ABSTRACT
    INTRODUCTION
    SUBJECTS AND METHODS
    RESULTS
    DISCUSSION
    REFERENCES


    Background: Evidence is increasing for positive effects of fruit and vegetable intakes on bone health. However, most of the studies to date were conducted in adults, and few reports included adolescents.

    Objective: We explored the association between bone mineral status and fruit and vegetable intakes in adolescent boys and girls (aged 16–18 y), young women (aged 23–37 y), and older men and women (aged 60–83 y).

    Design: Bone mineral measurements of the whole body, hip, and spine were made in all subjects by using dual-energy X-ray absorptiometry. Information on health and lifestyle and physical activity was obtained by questionnaire. Fruit, vegetable, and nutrient intakes were ascertained from 7-d food diaries.

    Results: In adolescent boys and girls and older women, significant positive associations were observed between spine size-adjusted bone mineral content (SA-BMC) and fruit intake. In boys only, femoral neck SA-BMC was also significantly and positively associated with the intakes of both fruit and dietary vitamin C. No significant associations were found in the young women or older men, or between bone measurements and intake of vegetables alone (after adjustments) in any of the groups.

    Conclusions: Higher fruit and vegetable intakes may have positive effects on bone mineral status in both younger and older age groups, especially at the spine and femoral neck. The specific mechanisms remain to be ascertained, but vitamin C, other fruit-specific antioxidants, and lifestyle may play a role.


    Key Words: Fruit and vegetables • bone mineral content • bone mineral density • adolescents • adults


    INTRODUCTION
    TOP
    ABSTRACT
    INTRODUCTION
    SUBJECTS AND METHODS
    RESULTS
    DISCUSSION
    REFERENCES


    Osteoporosis is a major public health problem in the United Kingdom and around the world. The deterioration in bone mass and microarchitecture associated with the disease leads to greater risk of fragility fracture, disability, and premature mortality. Diet is one of the modifiable risk factors for osteoporosis, and adequate dietary calcium intake and vitamin D status have long been recognized as factors in maintaining bone health (1). As long ago as 1968, it was suggested that a diet emphasizing fruit and vegetables and moderate amounts of milk should be considered as an adjunct to therapy for osteoporosis (2). Renewed interest in fruit and vegetable intakes came with the publication of several cross-sectional studies showing a positive link between bone mineral density (BMD) and fruit and vegetable consumption in adult men and women (3–9). However, studies involving postmenopausal women have not shown any association (9, 10). A 3-mo intervention study in 23–76-y-old men and women showed that consumption of a diet high in fruit and vegetables [ie, the Dietary Approaches to Stop Hypertension (DASH) diet] resulted in a significant reduction in bone turnover markers (3), which, if sustained for the long term, could result in bone mineral gains.

    The mechanism whereby fruit and vegetables may affect bone is not clear and may be multifactorial. A higher dietary acid load (caused by greater consumption of acid-forming foods, such as cereals and meat, than of alkali-forming foods, such as fruit and vegetables) is believed to result in bone mineral dissolution and greater bone resorption, which results in the release of carbonate, citrate, calcium, sodium, and potassium (11). A diet rich in fruit and vegetables may result in a more alkaline environment, which has been shown to reduce urinary calcium excretion (12). Fruit and vegetables also are rich sources of antioxidant vitamins such as vitamin C and &szlig;-carotene. These could act by combating oxidative stress, which has been shown to be negatively associated with BMD in adults (13). Vitamin C also has an essential regulatory role in osteoblast differentiation (14) and collagen formation and therefore may positively influence bone health (15–17). Vegetables are the principal source of vitamin K1 in the diet, and evidence is growing that vitamin K1 has a role in bone mineralization by acting as a cofactor in the -carboxylation of the bone protein osteocalcin (18–20). More emphasis is now being placed on the diet as a whole in relation to bone health rather than on isolated nutrients, but the evidence linking fruit and vegetables to bone health across the life cycle is not conclusive.

    The principal aim of the current study was to investigate the associations between bone mineral status and actual fruit and vegetable intakes, as estimated from 7-d food diaries. This study used data collected previously from 3 different studies including 5 cohorts—adolescent boys and girls, young women, and older men and women aged 16–83 y. Bone mineral status was assessed by size-adjusted (SA) bone mineral content (BMC) and bone mineral density (BMD). These measures were related to fruit and vegetable consumption after adjustment for other dietary and lifestyle factors. The secondary aim of the project was to investigate whether vitamin C, specifically, was exerting an influence on bone mineral status.


    SUBJECTS AND METHODS
    TOP
    ABSTRACT
    INTRODUCTION
    SUBJECTS AND METHODS
    RESULTS
    DISCUSSION
    REFERENCES


    Subjects
    The adolescent subjects, 125 girls and 132 boys aged 16–18 y, had been recruited from local schools and colleges to take part in the Cambridge (United Kingdom) Bone Studies (21–23). The adult subjects also were recruited from the Cambridge area. The 120 young women were between 23 and 37 y old. They either were nulliparous or had not given birth in the past 2 y or lactated for 1 y and had been recruited for the Young Women's Pregnancy Study (an ongoing study within the research unit). Recruitment was through advertisements, from the volunteer lists maintained at MRC Human Nutrition Research, or by word of mouth. The older subjects, recruited for the Vitamins K and D Study (24), were 70 men and 73 women aged 60–83 y. They were recruited through advertisements placed in general practitioners' offices and by recruitment presentations at retirees' associations. Exclusion criteria for all subjects included any medical condition, a history of any eating disorder, and current medication known to interfere with bone and calcium metabolism [except the contraceptive pill and hormone replacement therapy (HRT)]. Seven percent of the girls and 46% of the young women were taking a contraceptive pill, and 19% of the older women were currently receiving HRT. No dietary advice was given to the subjects.

    All volunteers and their parents or guardians (for the adolescents' study) gave written informed consent. Ethical approval for the adolescents' study was provided by the Ethics Committee of the MRC Dunn Nutrition Unit (now MRC Human Nutrition Research). Ethical approval for the young adult women's and the older men and women's studies was provided by the Cambridge Local Research Ethics Committee.

    Anthropometric and bone mineral status measurements
    In all subjects, height was measured to the nearest 0.1 cm by using a stadiometer (Doherty premier height measure; Sidhil Ltd, Halifax, United Kingdom). Weight was measured to the nearest 0.1 kg by using an electronic digital scale (Seca Scale; Todd Scales Ltd, Norwich, United Kingdom).

    In adolescent girls and boys, BMC (g) and bone area [(BA) cm2] of the whole body, lumbar spine (L1–L4), and left hip (total, femoral neck, and greater trochanter) were measured by using dual-energy X-ray absorptiometry (DXA) in a Hologic QDR 1000/W scanner (Hologic Inc, Waltham, MA). DXA software (version 5.61; Hologic Inc) was used for whole-body measurements (enhanced analysis), and the performance mode (version 4.47P) was used for spine and hip measurements. In young women and older men and women, the BMC and BA of the whole body, lumbar spine, and hip were measured by using a Lunar MD DXA scanner (GE Lunar, Madison, WI (software 4.7d). Quality assurance was performed daily, and long-term instrument stability was assessed 2–3 times/wk.

    Dietary intakes
    All subjects were asked to complete a prospective 7-d food diary; dietary records were obtained from 84% and 76% of the boys and girls, respectively; from 75% of the young women; and from 94% and 85% of the older men and women, respectively. Portion sizes were matched against food photographs, and quantities were described in household measures. The subjects were asked supplementary questions about their diet, such as the type of milk they usually drank, the type of fat used for cooking or spreading, whether they ate meat, and the type of water they drank. The diet records were coded by using the in-house software program, Diet In Data Out (DIDO; 25), and nutrient analysis was performed by using the in-house suite of software programs based on McCance and Widdowson's The Composition of Foods: the 4th (26) and 6th (27) editions for the adolescents and the older cohorts, respectively, and the supplements for cereal and cereal products (28) and milk and milk products (29). The 2 editions were used because dietary data were collected from the adolescents several years earlier than from the older cohorts. Intakes of calcium included calcium from the recorded intake of water, which was coded as Cambridge tap water unless otherwise specified. The analysis software allowed certain related items of foods to be grouped together to find the total weight of those related foods eaten per day. For the purposes of this investigation, total vegetable intake included green vegetables, root vegetables, pulses, salad vegetables including tomatoes, other vegetables, and mixed-vegetable dishes such as curries and stir-fry dishes, but it did not include potatoes. Total fruit intake included fresh fruit, cooked or canned fruit, dried fruit, nuts, and fruit juices. Only fruit and vegetables specifically reported were assessed; it was not possible to infer the contribution from composite dishes unless the contents were described by the subject.

    Physical activity, health, and lifestyle
    Habitual physical activity was ascertained in adolescent boys, young women, and older men and women by using the European Prospective Investigation into Cancer (EPIC) physical activity questionnaire (30). Activity levels in the adolescent girls were assessed by using a questionnaire adapted from the Allied Dunbar Fitness Survey UK, 1992 (31). For the purposes of this study, the measure of physical activity used was the total h/wk spent on recreational activities.

    Other relevant information was collected from the subjects by using a general health and lifestyle questionnaire. Details of smoking habits and dietary supplement use were recorded for all subjects. Information was obtained on the use of the contraceptive pill use by the girls and young women and on the use of HRT by the older women. The girls were asked their age at menarche, and the older women were asked their age at menopause.

    Statistical analysis
    Data analysis was performed by using SPSS for MS WINDOWS software (version 10.0; SPSS Institute, Chicago, IL). Because the data for this project came from 3 separate studies, each of which used a different sampling method, all statistical analyses were stratified by *** and age group. Descriptive statistics (ie, means, SDs, medians, and interquartile ranges) were ascertained for all variables. To correct for skewed distributions and to examine proportional associations, all bone data and the weights of foods were converted to natural logarithms. Multiple linear regression analysis was carried out on log-transformed data and the associations between bone at each of the sites and intakes of fruit, vegetables, combined fruit and vegetables, intake and vitamin C were ascertained. When regression analysis was carried out with the use of log-transformed data and when the independent variable was continuous, the regression coefficient multiplied by 100 corresponded closely with the percentage of change in the dependent variable associated with each 100% change in the independent variable, as defined by (difference/mean) x 100 (32). Therefore, the results of the regression analysis are presented as percentage coefficients.

    Univariate analysis was first carried out to examine the associations between BMC, BA, and BMD and fruit, vegetable, combined fruit and vegetable, and vitamin C intakes. Backward stepwise regression analysis was then carried out to ascertain the associations with BMC and BMD after adjustment for potential confounders [ie, age, total energy intake, calcium intake, vitamin K1 intake, supplement use, smoking, time spent per week in recreational activities, age at menarche (girls only), contraceptive pill use (girls and young women), age at menopause (older women only), and current HRT use (older women only)]. Because BMD may not adequately correct for bone and body size, models were also constructed in which BMC was adjusted for BA, height, weight, and the confounders listed above (SA-BMC model; 33). Results from the parsimonious models are presented as mean (±SE) percentage coefficients. In addition, for the older subjects only, to compare with an earlier publication (7), a further model was constructed in which BMD was the dependent variable, and height, body mass index (BMI; in kg/m2), age, total energy intake, supplement use, smoking, time spent in recreational activities, age at menopause, and HRT use were included as independent variables.

    When significant associations with fruit intake were found in groups (adolescents and older women), analysis of variance was used to compare the mean intakes of energy and selected nutrients by thirds of fruit intake. Scheffe's test was performed to indicate significant differences between the thirds. For those vitamins with very skewed distribution, the analysis was carried out by using log-transformed data. Means and 95% CIs for each third are reported.

    Results were not compared across the cohorts because the data were not collected at the same time and the assessments of bone mineral status were carried out with the use of different equipment. Each cohort had 80% power to detect correlations of 0.2 to 0.3 between bone mineral measurements and the consumption of fruit, vegetables, and combined fruit and vegetables.

    To assess the likely validity of the reported energy intakes, the ratio of energy intake to the basal metabolic rate was calculated (34); a ratio of <1.1 was taken to indicate energy underreporters. Associations between bone mineral measurements were ascertained with and without underreporters.


    RESULTS
    TOP
    ABSTRACT
    INTRODUCTION
    SUBJECTS AND METHODS
    RESULTS
    DISCUSSION
    REFERENCES


    Subject characteristics
    General characteristics of subjects including age, weight, height, BMI, age at menarche, age at menopause, HRT use, contraceptive use, smoking, and hours of physical activity per week are shown in Table 1. Table 1 also shows the summary statistics for BMC, BA, and BMD of the whole body, spine, total hip, trochanter, and femoral neck for all subjects. It should be noted that the Lunar DXA gives systematically higher BMD values than does the Hologic DXA (35).




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    Table 1 General characteristics and summary statistics for bone area and mineral measurements of whole body, spine, total hip, femoral neck, and trochanter in boys, girls, young women, and older men and women1




    When the estimates of total EI were compared with the calculated BMR, it was found that 12% of the boys and 8% of the girls were potential underreporters (36). In the young women, 20% were found to have a ratio of energy intake to basal metabolic rate of <1.1; in older men and women, the proportion was 3% and 12%, respectively. Inclusion of the underreporters made no difference to the bone-diet associations.
    Intake of fruit and vegetables
    The arithmetic mean, median, and interquartile range for intakes (by wt) of total fruit (including nuts and juices), fruit juices (from the total fruit intake), vegetables (not including potatoes), and total fruit and vegetables consumed by each of the age groups are shown in Table 2. Intakes of fruit and vegetables increased with age and were greatest in the older women. Only the older subjects, who were >60 y old, consumed an average of more than the recommended 400 g/d. Fifty-four percent of the women and 49% of the men had individual mean intakes 400 g/d. The intake of nuts was very small—a mean of 4.7, 4.1, 5.6, and 2.7 g/d for adolescents, young women, old men, and old women, respectively.




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    Table 2 Daily intakes of fruit and vegetables in adolescent boys, girls, young women, and older men and women1




    Associations between bone measurements and fruit and vegetable intakes
    The univariate associations between BMC, BA, and BMD and intakes of fruit, vegetables, and combined fruit and vegetables in boys and girls are shown in Table 3. In the boys, significant positive associations were found between BMC, BA, and BMD and fruit alone and combined fruit and vegetables at nearly all skeletal sites. For vegetables alone, significant associations were found only with whole-body and femoral neck BMC and whole-body BA. In the parsimonious multiple regression models, whole-body, total hip, femoral neck, and trochanter BMD and femoral neck and spine SA-BMC were significantly and positively associated with fruit and combined fruit and vegetable intakes, as shown in Table 4.



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    Table 3 Results of univariate analysis between whole-body, spine, total hip, femoral peck, and trochanter bone mineral content (BMC), bone area (BA), and bone mineral density (BMD) and fruit, vegetable, and combined fruit and vegetable intakes in adolescent boys and girls1






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    Table 4 Associations between bone mineral measurements at the whole-body, spine, and hip sites and fruit and vegetable intakes in adolescent boys and girls and fruit intake in older women from parsimonious regression models1




    In the univariate analysis of the girls (Table 3), the only significant positive associations found were those between spine BMC and BMD and intakes of fruit alone and combined fruit and vegetables and that between whole-body BMD and combined fruit and vegetable intakes. In the parsimonious multiple regression models (Table 4), whole-body SA-BMC was significantly and positively associated with combined fruit and vegetable intakes, and spine SA-BMC was significantly and positively associated with fruit and combined fruit and vegetable intakes. Whole-body and spine BMD were significantly and positively associated with fruit intake, and the effect was greater when fruit and vegetables were combined
    In young women and older men, no significant associations were found between any of the skeletal sites and fruit and vegetable intakes (when examined separately or in combination). When the association between BMD at various skeletal sites and total fruit and vegetable intakes was extended to include height and BMI in older men [to allow a direct comparison with a previously published study (7)], no significant associations were found.

    In older women, significant univariate (negative) associations were found only between total hip and trochanter BA and fruit intake and between trochanter BA and combined fruit and vegetable intakes (results not shown). In the parsimonious regression model, a significant positive association was found between spine SA-BMC and fruit intake (Table 4). This showed that doubling the fruit intake would result in a 5% increment in BMC of the spine. Models similar to those used by Tucker et al (7) were constructed, and a significant (P 0.05) positive association between spine BMD and fruit intake was found (results not shown, but doubling the fruit intake would result in a 5.6% increment in BMD of the spine). Adjustment for energy underreporting did not change the results in any subject group.

    Dietary characteristics by levels of fruit consumption
    To further understand the associations found between SA-BMC and fruit intake in the adolescents and the older women, comparisons of energy and key nutrients were made between thirds of fruit intake. The results for adolescent boys and girls are shown in Table 5. In the adolescents and the older women, the highest third of fruit consumption was associated with significantly higher intakes of potassium, folic acid, and vitamin C than was the lowest third (results in older women not shown). In boys and girls, carotene intake was significantly greater in the highest third than in the lowest third of fruit intake. In boys only, intakes of calcium, vitamin E, and vitamin K1 were significantly higher in the highest third than in the lowest third of fruit intake, and there was a nonsignificant trend for protein intake and total weight-bearing activity to be higher (results not shown).




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    Table 5 Mean (and 95% CI) daily nutrient intakes by thirds (T) of total fruit intake in boys and girls1




    Bone mineral status and dietary vitamin C intake
    The associations between dietary vitamin C and BMC, BA, and BMD in the adolescents and older women are shown in Table 6. In boys, significant positive associations were found between dietary vitamin C and BMC and BMD at all skeletal sites and between dietary vitamin C and whole-body BA. No significant univariate association was found in the girls, and a significant negative association with hip BA was found in the older women. In the boys, the parsimonious model showed significant associations with whole-body BMD, spine and femoral neck BMD, and femoral neck SA-BMC (Table 7). Adjustment for energy underreporting did not change the results in any subject group.



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    Table 6 Results of univariate analysis between whole-body, spine, total hip, femoral neck, and trochanter bone mineral content (BMC), bone area (BA), and bone mineral density (BMD) and vitamin C intake in boys, girls, and older women1






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    Table 7 Associations between bone mineral content (BMC), bone mineral density (BMD), and size-adjusted BMC (SA-BMC) at the whole-body, spine, and hip sites and vitamin C intakes in adolescent boys1





    DISCUSSION
    TOP
    ABSTRACT
    INTRODUCTION
    SUBJECTS AND METHODS
    RESULTS
    DISCUSSION
    REFERENCES


    Fruit and vegetable intakes
    The results of this study show that higher fruit and vegetable intakes may have a positive effect on bone mineral status in adolescent boys and girls and older women, especially at the spine and femoral neck. Higher intakes of fruit and vegetables were associated with other diet and lifestyle characteristics that may have an overall beneficial effect on bone health.
    The World Health Organization recommended in 1990 that 5 portions of fruit and vegetables (400 g) be eaten per day to reduce the risk of chronic diseases, including cardiovascular disease and cancer (37). Only 25% of the adolescents, 38% of the younger women, and 50% of the older men and women in the current study had intakes 400 g/d. The figures for fruit and vegetable intakes indicate that some of the subjects did achieve intakes equaling or surpassing the recommendation, and, particularly in the boys, higher intakes were associated with better bone mineral status.

    Advantages and limitations of this study
    This study was more rigorous than were previous studies that reported a positive association between fruit and vegetable intakes and bone health. In previous studies, dietary information was collected with the use of food-frequency questionnaires and retrospective reporting of fruit and vegetable intakes in earlier life (4, 7, 38). The current study is, to our knowledge, the only study in which the weights of fruit and vegetables, estimated separately from a prospective diet record, have been related to bone mineral status. In addition, this was the only study in which the analysis was carried out with the use of SA-BMC as a measure of bone mineral status. It is considered that the use of BMD does not adequately correct for bone and body size, particularly in adolescent subjects (32).

    The main limitation of the current study was that the subjects were not nationally representative; they were generally affluent and well educated, and, as volunteers, all were well motivated. The mean intakes of fruit and vegetables of each age group or *** in this study were greater than those in age-matched, nationally representative samples (39–41). In addition, the number in subjects in each of the cohorts was low, albeit large enough to address the question posed.

    Fruit and vegetable intakes and bone health in adolescents
    Adolescence is a crucial period of bone growth during which maximization of peak bone mass may reduce the risk of osteoporosis later in life (42). However, there have not been many studies of this nature involving young people. McGartland et al (8) reported a higher heel BMD by using a Lunar PIXI bone densitometer in 12- and 15-y-old girls, but not in boys, who had a higher fruit intake. However, this association disappeared in the older girls when adjustment was made for height, weight, pubertal status, activity level, social class, alcohol, smoking, and use of a nutritional supplements. In the current study, after similar adjustments were made, the results showed that doubling the fruit intake of the girls (aged 16-18 y) could increase spine BMD by 2.3%. In the current study, compared with the study by McGartland et al, the boys and girls were older, different bone sites were examined, and the subjects' combined consumption of fruit and vegetables was considerably higher, 92 and 74 g/d, for boys and girls, respectively. Data contrary to those of McGartland et al but in closer agreement with the current study were obtained from a longitudinal study of 85 Canadian boys and 67 girls aged 8–20 y, which showed that intakes of fruit and vegetables had a significant effect on whole-body BMC in boys but not in girls (43). In that study, the increment in whole-body BMC was 22 g for a twofold increase in fruit and vegetable consumption, whereas, in the current study, doubling the mean fruit and vegetable intakes of the boys would result in a much greater increment (240 g) in the mean whole-body BMC.

    Fruit and vegetable intakes and bone health in adults
    Of the groups included in the current study, the adolescent boys probably had the most metabolically active bone, as indicated by the significantly higher concentrations of bone turnover markers (44) and by the fact that they were still growing. The young women appeared to be the most stable; they had the lowest concentration of bone turnover markers among the female subjects, whereas the older women may have been in a state of bone flux because of their postmenopausal status. No positive association between bone and fruit and vegetable intakes was found in the young women, and no significant difference was found between vegetarians and nonvegetarians. This finding contrasts with a study by New et al (4) in premenopausal women aged 45–49 y in whom lumbar spine BMD was greater in the higher quartiles of intakes of nutrients found in fruit and vegetables—potassium, magnesium, and vitamin C. However, our findings in boys, girls, and women aged >60 y are similar to those of New et al and suggest that the skeleton may be most susceptible to variations in diet during the growth and mineral consolidation of adolescence and again later in life, when bone loss is greater.

    Tucker et al (7) examined dietary patterns in men and women aged 69–83 y and identified a group of high fruit and vegetable consumers. Men in that group (mean vitamin C intake: 305 mg/d) had greater hip BMD (including femoral neck, trochanter, and Ward's area) than did men who consumed less fruit and vegetables. In the current study, using the same model as Tucker et al, we found no association between BMD at any site and fruit and vegetable consumption in the older men, whose mean intake of vitamin C, 99 mg/d, was very much lower. Although we did find a positive association between fruit consumption and spine BMD in the older women. we could not find a positive association with vitamin C intake.

    Vitamin C intake and bone health
    In the current study, vitamin C was positively associated with bone mineral status at several sites in boys only. In 371 girls and boys aged 11–17 y whom Gunnes and Lehmann (16) studied, results indicated that an increase of 10 mg/d in vitamin C would result in an increment of 0.001 g/cm2 in distal radius BMD. The current study showed that, for the same increase in vitamin C intake, the boys achieved a greater increment of 0.003 (whole-body) to 0.005 (femoral neck) g/cm2. However, there were no significant results in the current study in girls, most of whom were older than the girls in the study of Gunnes and Lehmann. Nor were there any significant results in any of the older groups in the current study. This finding contrasts with previously published studies, in which positive associations were shown between BMD and dietary vitamin C in older women (4, 9, 15, 17, 45) and older men (15). The mechanism whereby the association between dietary vitamin C and bone mineral status in the boys was affected could be the well-defined role of dietary vitamin C in bone formation.

    Bone health and the whole diet
    In the current study, a greater intake of fruit and vegetables may have been an indicator of a better diet as a whole, and thus the whole diet could have contributed to the positive associations seen. It is not surprising that intakes of nutrients such as vitamin C, carotene, and potassium, which could be considered as markers for fruit, were higher in the high fruit consumers than in the low fruit consumers. Intakes of protein, calcium, and vitamin E were also higher in the boys who were high fruit consumers than in those who were low fruit consumers, which may indicate that the former group follows a better diet overall. However, calcium was not found to be a significant determinant of bone measurements in the boys or in any other age group. When considering the effect of fruit and vegetables on bone health, it should be remembered that these foods are part of the whole diet and may also represent a healthier lifestyle.

    Conclusions
    The results of this study show that higher fruit and vegetable intakes may have positive effects on bone mineral status in adolescents and older women, especially at the spine (girls and older women) and femoral neck (boys). The specific mechanisms remain to be determined, but vitamin C and other fruit-specific antioxidants may play a role (M O'Connell, G Mishra, G Muniz, et al, unpublished observations, 2005; M O'Connell, G Mishra, A Prentice, F Ginty, unpublished observations, 2005), and this is an area that merits further investigation. In a separate study of the same subjects (44), no significant associations were found between SA-BMC and 2 different measures of renal net acid excretion estimated from the diet. So the associations found between fruit and vegetable intakes and bone mineral status in these subjects did not appear to be related to a more alkaline environment (44). A recommendation to increase fruit and vegetable intakes, particularly in young people, would be expedient, because indications are that intakes in this age group are generally very low, and the results in the current study show that a considerable enhancement of BMC could be achieved. Future investigations could include intervention studies, particularly in younger groups. The fact that we were unable to show any associations between fruit and vegetable intakes and bone mineral status in young women and older men should not be interpreted as meaning that there is no advantage to be gained by an increase in intakes in these groups. Bone mineral status is only one aspect of health in which greater fruit and vegetable intakes may have long-term beneficial consequences.



    ACKNOWLEDGMENTS

    We gratefully acknowledge the Food Standards Agency of the United Kingdom for funding this study and the Medical Research Council of the United Kingdom for continued support. We are grateful to the participants of the Cambridge Bone Studies (adolescent boys and girls), the Young Women's Pregnancy Study (the young women), and the Vitamins K and D Study (the older men and women) and for the participants' permission to use their samples and data. We also thank the following people for their invaluable contributions: S Levitt for data entry; A Gent for dietary coding; and S Nigdikar and L McKenna for bone metabolism marker analysis.

    GDM, FG and MAO were responsible for the conception and design of the study. AP, LY, and MAL collected the data. GDM, GM, and CJP analyzed the data, and AP provided significant advice on the analysis of the bone-related variables. CJP wrote the manuscript, and FG edited the manuscript. None of the authors had a financial or personal conflict of interest.


    REFERENCES
    TOP
    ABSTRACT
    INTRODUCTION
    SUBJECTS AND METHODS
    RESULTS
    DISCUSSION
    REFERENCES




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    Received for publication July 12, 2005. Accepted for publication January 10, 2006.
     
  8.   مشاركة رقم : 5    ‏2006-06-18
  9. منير الشيخ

    منير الشيخ قلم فضي

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    Effect of caffeine on lower esophageal sphincter pressure in Thai healthy volunteers


    Effect of caffeine on lower esophageal sphincter pressure in Thai healthy volunteers


    S. Lohsiriwat1, N. Puengna1, S. Leelakusolvong2

    SUMMARY. Caffeine affects many aspects of body function including the gastrointestinal system. A single-blinded experimental study was performed to evaluate the effect of caffeine on lower esophageal sphincter (LES) and esophageal peristaltic contractions in healthy Thai adults. The volunteers were six men and six women aged 19–31 years. Subjects drank 100 mL of water. Five wet swallows were performed 30 min after the drink. The basal LES pressure was continuously measured using esophageal manometric technique. They then consumed another 100 mL of water containing caffeine at the dose of 3.5 mg/kg body weight. The swallows and basal LES pressure monitoring were repeated. The results showed no change in basal LES pressure after a water drink while caffeine consumption significantly lowered the pressure at 10, 15, 20 and 25 min. The mean amplitude of contractions and peristaltic velocity were decreased at the distal esophagus at 3 and 8 cm above LES. The mean duration of contraction was decreased at the distal part but increased at the more proximal esophagus. The heart rate, systolic and diastolic blood pressures were increased significantly at 10–20 min after caffeine ingestion. This study indicated that caffeine 3.5 mg/kg affected esophageal function, resulting in a decrease in basal LES pressure and distal esophageal contraction, which is known to promote the reflux of gastric contents up into the esophagus.

    INTRODUCTION
    The lower esophageal sphincter (LES) maintains its tonic contraction to separate the intrathoracic esophagus with negative pressure inside from the intra-abdominal stomach with positive pressure inside. The LES dysfunction can lead to either gastro-esophageal reflux disease (GERD) or dysphagia. Certain food and drink such as fat and wine or even food causing marked hyperglycemia trigger relaxation or transient relaxations of the LES.1,2 There have been studies focusing on the effects of coffee and caffeine on occurrence of gastro-esophageal reflux or their effects on LES pressure both in asymptomatic subjects and in patients with GERD symptoms. The results from various centers are controversial and the experimental studies were all carried out in Caucasian subjects.37 In the Thai population, symptoms of heartburn, frequent belching, and epigastric discomfort are not rare. The consumption of coffee is on the increase. The difference in lifestyle and anatomical morphology may result in differing effects of caffeine on esophageal function.

    This study aimed to examine the effect of caffeine upon the LES and esophageal function in healthy Thai subjects who normally had no gastrointestinal symptoms. The esophageal manometry was used to assess esophageal function. The effect of caffeine on blood pressure and heart rate was also observed.

    MATERIALS AND METHODS

    This cross-sectional experimental study was performed during January to May 2002, after being reviewed and approved by Siriraj Ethics Committee on Research Involving Human Subject (No. 6/2002). Twelve healthy volunteers of both genders (6 male and 6 female) were studied at the GI motility laboratory, Division of Gastroenterology, Department of Medicine, Siriraj Hospital, Bangkok, Thailand. They were 19–31 years old, regular coffee consumers, more than three cups a week, and had never experienced symptoms such as tachycardia, palpitation, nausea or skin rash after coffee-drinking. The subjects used no medication at all at least 1 week before the experiment. A heavy smoker (more than 20 cigarettes/day) or a person having any diseases such as heart disease, diabetes mellitus, hypertension, cancer and gastrointestinal disorders was excluded.

    Esophageal manometry was performed with Mui system No 9043H0311 (MUI Scientific Company, Ontario, Canada). It is comprised of eight capillary tubes around a larger central tube with an overall diameter of 4.5 mm. One orifice locates at the distal margin to monitor intragastric pressure and six at 0, 3, 8, 13, 18 and 23 or 28 cm respectively from the upper margin of the sleeve sensor (Dent sleeve, Arndorfer Medical system, Greendale, WI, USA). The lumen of each tube was constantly perfused with distilled water at a rate of 0.3 mL/min. A pressure transducer was incorporated to each perfusion line and connected to a polygraph device.8 During the study, the manometric recordings were displayed on the screen of an online computer and were stored for later analysis with the use of a software program.

    Parameters measurable at the LES segment included: (i) the distal border of the LES (a persistent rise in pressure exceeding 2 mmHg above the end-expiratory gastric baseline): (ii) the proximal border of the LES (the pressure drops below the gastric baseline to the esophageal baseline); (iii) the overall length of the LES; (iv) the length from distal LES to proximal LES; (iv) the LES pressure (the maximum pressure at end-expiratory phase above the gastric baseline); and (vi) the degree of LES relaxation or the residual pressure on relaxation (the pressure difference between gastric baseline and the lowest sustained pressure at LES relaxation).

    Esophageal body functions to be evaluated were the amplitude and the duration of contraction together with propagation rate (velocity) of a contraction wave.

    Each subject completed a previously validated, self-administered questionnaire to assess medical history and gastrointestinal tract disorders. The questionnaire had 13 questions covering both upper and lower GI tract common symptoms.9 The symptoms were weight loss, painful or difficult swallowing, regurgitation after meals, hoarseness or chronic cough, hematemesis, epigastric pain, bloating, nausea after meals, melena, chronic diarrhea or constipation.

    The study was performed in a single-blind manner. Subjects signed an informed consent form after being clearly informed of the procedure. The questionnaire was completed. Each subject fasted for at least 4 h and refrained from smoking or any alcoholic drink overnight. Esophageal manometry was performed with the station pull-through technique of the LES pressure measurement (0.5–1.0 cm steps every 15 s). All the esophageal manometry parameters were recorded at least for 10 minutes as baseline values. Subjects consumed 100 mL water (control drink) and LES pressure was continuously recorded for 30 min. Subjects did five wet-swallows (5 mL of water each time) with LES pressure and esophageal waves recorded. Subjects then consumed another 100 mL drink containing 3.5 mg of caffeine/kg. The LES pressure measurement was conducted for another 30 min and another five wet-swallows were repeated with LES pressure and esophageal waves recorded.

    Before and at 10-minute intervals after ingestion of caffeine or the control drink, the arterial pulse rate was recorded. Systolic and diastolic blood pressures were also manually measured by the same registered nurse using the same sphygmomanometer throughout the experiment. These parameters were monitored to assess the duration of the systemic effect of caffeine on the cardiovascular system.

    Data were calculated by computer, using the SPSS statistical program. All basic parameters such as LES pressure, amplitude, duration and velocity were presented as mean plus and minus one standard deviation. Kolmogorov-Smirnov test was used to test the data distribution. Student's paired t-test was used to compare the data in the group with normal distribution or Wilcoxon's signed-rank test with non-normal distribution. A P-value < 0.05 was considered to be statistically significant.

    RESULTS

    The effects of caffeine on LES pressure and esophageal waves were studied in 12 healthy subjects using esophageal manometric method. Subject characteristics, temperature of the drinking solutions and amount of caffeine consumed are shown in Table 1.

    The results showed that caffeine 3.5 mg/kg produced a pronounced effect on the LES pressure as shown in Fig. 1. Drinking distilled water showed no effect on LES pressure. However, after the caffeine drink, the pressures decreased at 5 min and stayed low throughout the 30-minute monitoring period. The LES pressures after the caffeine drink were compared to those after a control drink at the same period of time. They were significantly lower at 10, 15, 20 and 25 min.

    The esophageal wave parameters examined were the peristaltic amplitude (in mmHg), the duration (in seconds) and the velocity (in cm/s) as shown in Table 2. After caffeine consumption, the mean esophageal peristaltic amplitude was significantly decreased at 3 cm and 8 cm above the LES portion. Duration of each esophageal peristaltic contraction on average decreased at 8 cm but increased at 13 cm above the LES portion. Velocity of each esophageal peristaltic wave was slightly decreased but without statistical significance. Post-deglutition relaxation of the LES remained unaffected by caffeine.

    Hemodynamic parameters including the heart rate, systolic and diastolic blood pressures, showed no change after water ingestion. On the other hand, after caffeine ingestion, the mean value of heart rate, systolic and diastolic blood pressures increased significantly at 30 min after caffeine ingestion as shown in Table 3.

    Only one male subject complained of mild palpitation after 30 min of drinking 306 mg caffeine while his heart rate rose from 72 beats/min before caffeine to 76 beats/min. The symptom spontaneously disappeared within a few minutes.

    DISCUSSION

    This study showed that, in healthy young people, caffeine 3.5 mg/kg produced a decrease in basal LES pressure at 10 min after consumption and was sustained throughout the monitoring period of 30 min. The mean esophageal peristaltic amplitude was decreased at the distal esophagus 3 and 8 cm above the LES. The duration of esophageal peristaltic contraction was decreased at the distal site 8 cm above the LES but increased at a more proximal site 13 cm above the LES. Velocity of the esophageal peristaltic wave was not significantly changed. The blood pressure and heart rate increased.

    The subjects could actually taste the bitter caffeine drink, so this was not blinded. The authors did not want to add other substances such as sugar or flavoring into the drink as it may have interfered with the result. However, we detected no report of psychological effects on LES pressure or lower esophageal body contractions.

    The effect of caffeine on basal LES pressure has been studied by many investigators but the results and mechanisms of action are controversial. Cohen et al. in 1975 showed that caffeine at 4.6 mg/kg did not change basal LES pressure in Caucasian subjects.3 The technique used in 1975 might not be as accurate. Many pitfalls have been corrected so far. In this present study, the manometry was performed with an MUI system, which is somewhat different from that which has been used in Western laboratories. The difference in technology is also a limitation factor in comparing the data.

    The mechanism of action of caffeine on LES pressure is still not established. Caffeine may affect the LES via the neurohormonal system. Goyal in 1980 found that the main intramural innervation of the LES consisted of inhibitory nerves that released inhibitory neurotransmitters such as vasoactive intestinal polypeptides.10 Caffeine may stimulate the gut hormonal system to release cholecystokinin (CCK) or gastrin which produces a lower LES pressure via inhibitory neuron stimulation. Van Deventer G et al. in 1992 found that coffee resulted in higher blood gastrin levels.11 Gastrin is a potent known stimulant of LES smooth muscle activity.12 The present study showed a significant LES pressure decrease after a caffeine drink which is not in concordance with the effect of coffee on gastrin. It is possible that, besides gastrin stimulation, caffeine also exerts other actions directly or indirectly on LES. The study by Douglas et al. in 1990 showed that regular coffee induced significant increases in plasma CCK over basal concentration13 and both exogenous (octapeptide-CCK) and endogenous CCK can reduce resting LES pressure.14,15 The decrease of LES pressure after a caffeine drink might be the result of caffeine effects via the stimulation of CCK release. CCK can also stimulate receptors on inhibitory neurons and induce the release of nonadrenergic, non-cholinergic (NANC) inhibitory neurotransmitters such as nitric oxide (NO). NO has been implicated as a major inhibitory neurotransmitter in the NANC nerves. In vivo studies have demonstrated that NO is a mediator of LES relaxation induced by swallowing.16,17

    Gastric distension by balloon has been shown to increase LES pressure in humans.18 In the present study, the decreased LES pressure did not appear to be the effect of gastric distension because the total volume of water or caffeine in each drink was only 200 mL.

    In summary, caffeine can reduce basal LES pressure significantly. The decreased LES pressure is a risk factor augmenting the gastric content refluxes into the esophagus, which may produce heartburn. Not only the lower basal LES pressure can induce GERD, but also the transient LES relaxation (TLESR) can be a principle mechanism of acid GERD in humans and dogs.19,20 In this study, the TLESR phenomenon was found only in one female subject and it occurred both after water and caffeine ingestion.

    This present study might indicate that this group of Thai subjects was sensitive to caffeine (3.5 mg/kg). Therefore, the risk of reflux of gastric contents in Thai subjects may be substantial if they frequently consume strong caffeine-containing food or drink. However, in this study high dose caffeine was used (147–304 mg). One teaspoonful of instant coffee contains only approximately 80 mg caffeine. It is possible that the amount which people generally consume each time may not be so high, but they should be aware that the half-life of caffeine is up to 5 h,21 which has significance if they consume caffeine in high concentrations or frequently.

    This study also demonstrated the effect of caffeine on esophageal primary peristaltic (swallow-induced) contractions. Caffeine may exert its effect both on the central swallowing mechanism in the brain or the peripheral motor mechanism of peristaltic contraction. It is possible that the effect of caffeine on esophageal peristalsis may be produced via NO pathway. Swallow-induced esophageal contractions involve both the cholinergic and NO pathways.22 However, the response of the proximal and the distal esophageal sites are slightly different. In a review paper,23 was is generally accepted that the proximal esophageal muscle fibers behave more like striated muscles while those of the distal parts are smooth muscle fibers. This may explain the different responses to a chemical-like caffeine in both parts of the esophagus. Although the amplitude of peristaltic contractions decreased, the pressure is still well over the amplitude threshold needed for effective volume clearance (10 mmHg in the proximal esophagus and 30 mmHg in the distal esophagus).24,25

    The velocity of contractions in the distal esophagus measured in this present study was rather constant at approximately 2.3–2.5 cm/s either before or after a water or caffeine drink. This mean value is lower than the reference from Caucasian subjects (approximately 3 cm/s in the proximal esophagus and 3.5 cm/s in the distal esophagus).26

    Characteristics of the swallowed bolus certainly affect the peristaltic response. Dry swallows result in lower amplitude waves that are not very reproducible. Liquid boluses greater than 2 mL give more reproducible waves of higher amplitude.27 The temperature of the bolus is also important. Single cold water swallows (0.5–3.0°C) markedly decrease the frequency of peristalsis in the esophagus, slow the speed of peristalsis throughout the esophagus, and prolong the duration of the peristaltic wave in the distal esophagus. On the other hand, hot water (58–61°C) slightly increases the peristaltic frequency in the proximal esophagus, and shortens the contraction duration throughout the esophagus.28 The range of temperature and volume used in this experiment correspond with that of normal drinking and should exert no effects on esophageal functions.

    In the present study, the effect of caffeine on blood pressure and heart rate were also evaluated. After the control drink of distilled water, the blood pressure and heart rate tended to decrease. This might be due to effects of rest. On the contrary, after caffeine ingestion, the mean value of heart rate, systolic blood pressure and diastolic blood pressure increased significantly at 10 and 20 min. The increase of heart rate and blood pressures is caused by the sympathetic nervous system stimulation. Thomas et al. (1984) described that caffeine caused an increase in blood pressure as a result of an increase in total peripheral vascular resistance, either secondary to caffeine's ability to block purinergic (vasodilator) receptors or enhanced sympathetic activity.29

    CONCLUSION

    The esophageal manometric parameters in healthy Thai subjects obtained from this study indicated that the basal LES pressure and esophageal peristaltic contraction amplitudes were decreased after caffeine ingestion. This effect of caffeine may produce gastric reflux and induce GERD. Though the lowered contraction amplitude and peristaltic velocity observed in this study are still well above the threshold for effective esophageal volume clearance, the caffeine effect in patients with GERD should be examined. The study also showed that caffeine exerted some effects on the cardiovascular system. Individuals with gastrointestinal or cardiovascular symptoms should be cautious in consuming caffeine-containing food or drinks.


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