To the Editor We read with interest the findings published by Stratakis et al1 in JAMA Pediatrics regarding the association between maternal fish intake during pregnancy and child growth.1 The authors reported that relatively high maternal fish intake was positively associated with childhood obesity. The authors suggested that the biological mechanisms that may explain this association were ω-3 long-chain polyunsaturated fatty acids and/or environmental contaminants. However, the authors had not discussed the potential role of other nutrients that are available from fish. It is well documented that fatty fish is a major dietary source of vitamin D. In accordance with results on ω-3 long-chain polyunsaturated fatty acids, studies that have examined the association between maternal vitamin D during pregnancy and childhood adiposity have yielded conflicting results that are slightly weighted toward a negative, or beneficial, association in childhood.2- 4 The heterogeneity of ages at which the offspring are assessed for markers of adiposity provides 1 plausible explanation for conflicting results in the literature; the relatively young age of participants in the study by Stratakis et al1 (aged up to 6 years) may explain the positive association observed. Indeed, data from the Southampton Women’s Survey2 reported that the positive association observed between maternal vitamin D status and adiposity at birth changed to a negative association when the same children were aged 6 years.2 It is plausible that a similar trajectory of growth might be observed with regards to maternal fish intake and adiposity in offspring, especially if these associations are examined in cohorts of older children; however, in this study, the positive relationship is still evident at aged 6 years. In this sense, it is perhaps the endocrine-disrupting environmental contaminants in fish that may be counteracting any beneficial effects of ω-3 long-chain polyunsaturated fatty acids and vitamin D on offspring adiposity. As noted by the authors of this study, future analyses using more precise indices of adiposity, such as dual-energy x-ray absorptiometry, may assist with elucidating the relationship between maternal fish intake during pregnancy and childhood obesity. Furthermore, the addition of direct measures of maternal serum levels may help to clarify which nutritional and environmental constituents in fish are biologically responsible for these associations.
Hyde NK, Brennan-Olsen SL, Pasco JA. Fish Intake During Pregnancy and Offspring Adiposity. JAMA Pediatr. 2016;170(8):809. doi:10.1001/jamapediatrics.2016.1046