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Providing perspectives on recent research into vitamins and nutritionals


Child Development More Sensitive to Maternal Intake of DHA than Mercury Found in Fish

By Michael McBurney

Fish and shellfish contain high-quality protein, omega-3 fatty acids and are low in saturated fat. However, nearly all fish and shellfish contain mercury. Mercury is a neurotoxin to the brain and nervous system. Both the Food and Drug Administration (FDA) and Environmental Protection Agency (EPA) advise women who are pregnant, may become pregnant, are nursing and their young children to avoid certain types of fish (shark, swordfish, king mackerel, or tilefish).

Strain and colleagues investigated the relationship between maternal mercury exposure and child development in 1,265 mother-child pairs from a high fish-eating population. Maternal hair samples were obtained at delivery to determine mercury exposure. Non-fasting, total serum fatty acids were measured at 28 wk of gestation as a biomarker of omega-3 long-chain polyunsaturated fatty acids (LCPUFA) in the triacylglyerol fraction.

Mothers reported eating an average 8.5 fish meals per week. Prenatal methyl mercury concentrations were positively correlated with α-linolenic (ALA), eicosapentaenoic acid (EPA), and docosahexaenoic acid (DHA) concentrations. Methyl mercury concentrations were not statistically associated with measures of cognitive development [Mental Development Index, MDI] whereas DHA was significantly adversely associated with MDI score. PUFA status, independent of mercury status, was positively associated with improved communication. The authors write that higher maternal DHA status, and a lower omega-6 to omega-3 ratio, may be beneficial for child language and communication skills.

Low blood DHA has been previously associated with poor cognitive performance and behavior in school-age children (7-9y). Increasing DHA intake improved reading performance in children with low reading skills.

DHA and EPA isolated as oils from fatty fish can be deodorized and purified. For this reason, omega-3 supplements in the form of fish oils, as well as algal sources, decrease risk of mercury ingestion. It is almost impossible to ingest hazardous levels of mercury from purified DHA and EPA supplements.

There are alternatives to eating fish multiple times a week. But even when mother-child pairs eat lots of fish, this research finds the benefits of DHA and EPA outweigh the risks of mercury in young children.

Main Citation

Strain JJ, Yeates AJ, van Wijngaarden E, Thurston SW, Mulhern MS, McSorley EM, Watson GE, Love TM, Smith TH, Yost K, Harrington D, Shamlaye CF, Henderson J, Myers GJ, Davidson PW. Prenatal exposure to methyl mercury from fish consumption and polyunsaturated fatty acids: associations with child development at 20 mo of age in an observational study in the Republic of Seychelles. 2015 Am J Clin Nutr doi: 10.3945/ajcn.114.100503

Other Citations

Montgomery P, Burton JR, Sewell RP, Sprecklesen TF, Richardson AJ. Low blood long chain omega-3 fatty acids in UK children are associated with poor cognitive performance and behavior: A cross-sectional analysis from the DOLAB study. 2013 PLoS ONE doi:10.1371/journal.pone.0066697

Richardson AJ, Burton JR, Sewell RP, Spreckelsen TF, Montgomery P. Docosahexaenoic acid for reading, cognition and behavior in children aged 7-9 years: A randomized, controlled trial (The DOLAB Study). 2012 PLoS One doi: 10.1371/journal.pone.0043909