The mercury doesn't affect the developing brain of the newborn and small child, even though their mothers had been eating a great deal of fish during pregnancy, scientists from the University of Rochester have discovered.
The fish's polyunsaturated fatty acids (PUFAs)-known as n3-have anti-inflammatory qualities, and this seems to counteract the mercury.
The researchers noticed that children born in the Seychelles had normal brain development and learning abilities, even though their mothers were eating an average of 12 fish meals each week when they were pregnant.
Previous researchers had assumed the benefits of the fatty acids outweighed the bad effects of the mercury, but the new study found a more complex interplay between the PUFAs and mercury.
They tracked the diets and health of more than 1,500 mothers and children, and, at 20 months, the children were tested for their communication skills, behaviour and motor skills, while hair samples from the mothers were tested for mercury levels.
Even the children of mothers with the highest mercury levels were developing normally.
Mercury gets into the oceans from natural and human activity, such as emissions from coal plants.
(Source: American Journal of Clinical Nutrition, January 2015; doi: 10.3945/ajcn.114.100503)