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21 January 2015 - Medicalxpress - Fatty acids in fish may shield brain from mercury damage

New findings from research in the Seychelles provide further evidence that the benefits of fish consumption on prenatal development may offset the risks associated with mercury exposure.

In fact, the new study, which appears today in the American Journal of Clinical Nutrition, suggests that the nutrients found in fish have properties that protect the brain from the potential toxic effects of the chemical.

Three decades of research in the Seychelles have consistently shown that high levels of fish consumption by pregnant mothers - an average of 12 meals per week - do not produce developmental problems in their children. Researchers have previously equated this phenomenon to a kind of biological horse race, with the developmental benefits of nutrients in fish outpacing the possible harmful effects of mercury also found in fish. However, the new research indicates that this relation is far more complex and that compounds present in fish - specifically polyunsaturated fatty acids (PUFA) - may also actively counteract the damage that mercury causes in the brain.

The study published today followed more than 1,500 mothers and their children. At 20 months after birth, the children underwent a battery of tests designed to measure their communication skills, behavior, and motor skills. The researchers also collected hair samples from the mothers at the time of their pregnancy to measure the levels of prenatal mercury exposure.

The researchers found that mercury exposure did not correlate with lower test scores. This finding tracked with the results of previous studies by the group - some of which have followed children in the Seychelles into their 20s - that have also shown no association between fish consumption and subsequent neurological development.

The researchers also measured the PUFA levels present in the pregnant women and found that the children of mothers with higher levels of fatty acids known as n3 - the kind found in fish - performed better on certain tests. Another common form of PUFA, called n6, comes from other meats and cooking oils and is found in greater abundance in the diets of residents of developed countries.

The fatty acids in fish (n3) are known to have anti-inflammatory properties, compared to n6, which can promote inflammation. One of the mechanisms by which mercury inflicts its damage is through oxidation and inflammation and this has led the researchers to speculate that not only does n3 provide more benefit in terms of brain development, but that these compounds may also counteract the negative effects of mercury.

This was reflected in the study's findings, which showed that the children of mothers with relatively higher levels of n6 did poorer on tests designed to measure motor skills.

"It appears that relationship between fish nutrients and mercury may be far more complex than previously appreciated," said Philip Davidson, Ph.D., the principal investigator of the Seychelles Child Development Study, a professor emeritus at the University of Rochester, and senior author of the study. "These findings indicate that there may be an optimal balance between the different inflammatory properties of fatty acids that promote fetal development and that these mechanisms warrant further study."