This paper reports dietary intakes during pregnancy and maternal serum fatty acid concentrations and breast milk in a sample of pregnant women, in the Republic of Seychelles where habitual fish consumption is high.
We found that the fatty acid composition of serum from pregnant women in the Seychelles who consume fish daily to be similar to that observed for other populations. [29
] The concentration of both maternal DHA and AA in serum fell between 28 weeks gestation and delivery; a decrease that remained significant for DHA after adjusting for confounding factors. This fall has been observed in other studies [7
] and is believed indicative of increased accretion of LCPUFAs for the development of neural tissue by the fetus. DHA status in maternal serum phospholipids has been observed to be lower in multiparous than in primiparous women. [30
] This inverse association has been attributed to the delay (up to six months post partum) for LCPUFA status to return to pre-pregnancy levels. [31
] In contrast, we observed a positive association between parity and serum DHA. This finding is partly supported by Dunstan et al, [12
] who observed no association between parity and LCPUFA status of erythrocyte phospholipids in women supplemented with fish oil and concluded that, if adequate LCPUFAs are available from the diet, DHA depletion associated with pregnancy can be avoided. Postnatal rapid repletion of maternal DHA status may have benefits for children born from subsequent pregnancies.
We did not find any association between maternal DHA status and the length of gestation, a finding which has previously been reported in both observational and intervention studies [32
]. Furthermore, we found no evidence of the previously reported association between maternal DHA status and neonatal birth weight. [19
] However, our findings are in agreement with other observational [34
] and n-3 PUFA intervention studies [14
] and supported the conclusions of Desci & Koletzko [37
] who after reviewing the literature concluded that no unequivocal effect of LCPUFA status was evident. We speculate that associations among DHA status and neonatal outcomes may only be evident in populations where DHA status is limiting and may not be apparent in populations such as the current one where fish (and thereby DHA) intake are high.
Fish consumption in the Seychelles is high compared to other populations. In the UK, average fish consumption is 140 g/week.[22
] In the Seychelles the mean weekly intake of fish was 527 g. Recommendations for fish intake in pregnancy are generally based on obtaining adequate intakes of n−3 PUFAs but concerns of adverse effects of prenatal methylmercury exposure have lead to stringent guidelines being set. The UK Scientific Advisory Committee on Nutrition [22
] base their recommendations on consuming not more than 2 ×140 g portions of oily fish per week (rich in n-3 PUFAs) whereas the US FDA and US EPA jointly recommend not more than 2 × 170 g portions of fish (low in mercury) a week for pregnant women.[23
] A recent publication by Hibbeln at al [38
] found no evidence to support the US advisory on fish intake in pregnancy. In a large cohort of pregnant women (n = 11875) low fish intake (< 340 g/week) did not protect against adverse outcomes. Conversely, fish consumption exceeding 340g/wk was associated with beneficial effects on child development. The population in Seychelles currently exceeds both thee UK and US recommendations, albeit fish consumption is declining. Changes in the traditional diet have been observed in Seychelles with a two fold increase in the per capita consumption of eggs and chicken and a three fold increase in processed meats between 1983 and 1992 leading to a 36 % decrease in fish intake per capita.[39
] In keeping with this trend we did observe a significant correlation between age of mother and dietary fish intake (data not shown) with younger mothers consuming less fish.
Dietary fish intake, as estimated from the food diaries, did not correlate with LCPUFA status in either maternal serum or breast milk. These findings are supported by recently published work demonstrating no relation between concentrations of n−3 fatty acids in serum and total dietary fish intake [40
] in non-pregnant volunteers and are in agreement with other studies in high fish consuming populations.[41
] It is highly likely that fatty acid status in pregnant women is influenced by a number of physiological pregnancy related factors, not least fetal requirements, so it is perhaps not surprising that such associations were not evident. Measurement error from self-reporting of habitual diet is also a potential confounding factor although the reporting error, if any, associated with estimating portion sizes would likely have been consistent between subjects as only one trained nutritionist at the was responsible for the interpretation and entry of dietary data.
The concentrations of the various fatty acids observed in breast milk at one month postpartum were similar to those reported in other populations. A comparative study of breast milk samples from diverse populations reported concentrations of the saturated and monosaturated fats similar to those observed in the Seychelles. In this comparative study the DHA concentration of breast milk varied between 0.17 and 0.99 % with the highest DHA status evident in high fish eating populations from Asia. [42
] A recent metaanalysis incorporating 106 studies reported a mean DHA content of breast milk of 0.32 %, remarkably similar to the average of 0.31% observed in this study. [43
] The 1:1 ratio of AA to DHA observed in breast milk from Seychellois women is in keeping with a previous study undertaken in Tanzania.[44
] The authors of that study attributed their finding to the high fish consumption of the population. In contrast, studies in populations with lower fish intake report that the ratio of AA : DHA approaches 3:1 in breast milk.[45
] Whilst there is no gold standard defining optimal fatty acid status in formula milk, typical recommendations for term infants are AA ≥ 0.35 % and DHA ≥ 0.2%.[47
] Mean concentrations of AA and DHA in the breast milk of Seychellois women are 0.29 % and 0.31 % respectively. Thus, breastfed infants born to Seychellois women, who habitually consume a high fish diet, are receiving a DHA : AA ratio similar to that recommended for optimal development.
In conclusion, we report that even with high fish consumption, fetal accretion is so great that maternal status of DHA declines during the later stages of pregnancy. However, our results indicate that the n-3 : n-6 ratio in breast milk is high, which may exert potentially beneficial effects on cognitive development of breast fed children in Seychelles. Furthermore, our findings contribute to the ongoing debate on the influence of fatty acid status on gestational length and neonatal outcomes by the observation that in our high fish eating cohort fatty acid status is not a significant determinant of gestational length and neonatal anthropometric outcomes.