Fish intake during pregnancy aids brain development

Children born to mothers who regularly ate low-mercury fish during pregnancy may have sharper minds than their peers. Oily fish such as tuna, salmon and sardines contain omega-3 fatty acids, which are important in fetal and child brain development. The problem is that fatty fish are more likely to be contaminated with mercury, a metal that is toxic to brain cells, particularly in fetuses and young children. Because of this, pregnant women are advised to avoid certain fish altogether: shark, swordfish, king mackerel and tilefish. These fish are particularly high in mercury because they eat other fish and are long-lived, accumulating mercury in their fat tissue over time. Fish that are high in omega-3 but relatively lower in mercury include canned light tuna, which has less mercury than albacore tuna, and smaller oily fish like salmon. White-meat fish such as cod and haddock tend to be low in mercury, but have less omega-3 than fatty fish. American researchers collected blood samples from 341 women during their second trimester and asked them how often they ate various foods, including fish. When their children were three years old, they took standard tests of vocabulary, visual-spatial skills and fine-motor coordination of the hands and fingers. It was found that children whose mothers ate more than two servings of fish per week during pregnancy generally performed better on tests. However, children whose mothers had relatively higher mercury levels in their blood during pregnancy scored more poorly than those whose mothers had lower mercury levels. And mothers who regularly ate fish during pregnancy were more likely to have such mercury levels than non-fish-eaters. Only two per cent of mothers who never ate fish during pregnancy had blood mercury levels that high, versus 23 per cent of those who ate fish more than twice weekly. The findings suggest that though fish is considered a brain-food, it is the choice of fish that matters. Recommendations for fish consumption during pregnancy should take into account the nutritional benefits of fish as well as the potential harms from mercury exposure. However, further research is warranted to see if the benefits of other omega-3-containing fish outweigh the potential risks.