Positive benefits of eating fish irrespective of type
What mattered was not which types of fish were eaten but whether the woman ate fish or not, which emerged as the most important factor. The mother’s prenatal mercury level was positively associated with her child’s IQ if she had eaten fish in pregnancy, but not if she had not.
“Significantly beneficial associations with prenatal mercury levels were shown for total and performance IQ, mathematical/scientific reasoning, and birth weight, in fish-consuming versus non–fish-consuming mothers,” the authors said. “These beneficial findings are similar to those observed in the Seychelles, where fish consumption is high and prenatal mercury levels are 10 times higher than U.S. levels.”
Caroline Taylor, PhD, senior research fellow and coauthor of the study, said: “We found that the mother’s mercury level during pregnancy is likely to have no adverse effect on the development of the child provided that the mother eats fish. If she did not eat fish, then there was some evidence that her mercury level could have a harmful effect on the child.”
The team said that this was because the essential nutrients in the fish could be protective against the mercury content of the fish. “This could be because of the benefits from the mix of essential nutrients that fish provides, including long-chain fatty acids, iodine, vitamin D and selenium,” said Dr. Taylor.
Women stopped eating any fish ‘to be on the safe side’
The authors called for a change in official guidance. “Health advice to pregnant women concerning consumption of mercury-containing foods has resulted in anxiety, with subsequent avoidance of fish consumption during pregnancy.” Seafood contains many nutrients crucial for children’s growth and development, but “there is the possibility that some women will stop eating any fish ‘to be on the safe side.’ ”
The authors said: “Although advice to pregnant women was generally that fish was good, the accompanying caveat was to avoid fish with high levels of mercury. Psychologically, the latter was the message that women remembered, and the general reaction has been for women to reduce their intake of all seafood.”
Coauthor Jean Golding, emeritus professor of pediatric and perinatal epidemiology at the University of Bristol, said: “It is important that advisories from health professionals revise their advice warning against eating certain species of fish. There is no evidence of harm from these fish, but there is evidence from different countries that such advice can cause confusion in pregnant women. The guidance for pregnancy should highlight ‘Eat at least two portions of fish a week, one of which should be oily’ – and omit all warnings that certain fish should not be eaten.”
The study was funded via core support for ALSPAC by the UK Medical Research Council and the UK Wellcome Trust.
A version of this article first appeared on Medscape UK.