Fish really is brain food - for the fetus

NEW YORK - New research suggests that fish may indeed be brain food, at least those varieties that have low levels of mercury.

In a study of 135 mothers and their infants, researchers at Harvard Medical School in Boston found that mothers' fish consumption during pregnancy seemed to aid fetal brain development. Overall, the greater a woman's fish intake during the second trimester, the better her 6-month-old performed on a standard test of mental development.

On the other hand, when mothers had fairly high mercury levels - as measured in hair samples - their babies tended to have relatively poorer test scores.

The implication, according to the researchers, is that fish can be a brain-healthy food for women to have during pregnancy - but only if they eat varieties likely to have little mercury contamination.

Mercury is a metal that occurs in the environment both naturally and as a product of industrial pollution. Most fish and shellfish have some level of mercury, but certain large, long-lived fish are likely to accumulate high levels of the pollutant, which can damage the developing fetal brain.

Because of this, health officials in the US advise pregnant women to avoid certain fish, such as shark, swordfish, and king mackerel.

Yet fish also provide a number of important nutrients, including omega-3 fatty acids, which may support fetal brain development.

The new findings, published in the journal Environmental Health Perspectives, point up this potential benefit.

"Women should continue to eat fish during pregnancy but choose varieties with lower mercury contamination," conclude Dr Emily Oken and her colleagues.

Safer fish choices include canned light tuna, which has less mercury than albacore tuna, and other small fatty fish such as salmon, Oken said. White-meat fish, cod and haddock for example, tend to have low mercury levels - though, she noted, they also have lesser amounts of the beneficial omega-3 fats.

For their study, Oken and her colleagues questioned pregnant women about their fish intake during the second trimester and took hair samples in order to measure the women's mercury levels.

When participants' babies were about 6 months old, the researchers gave them a test that measured their visual memory.

The babies were shown a particular picture a number of times so they could become familiar with it. They were then shown that picture along with a second, new picture. The babies' scores were based on how long they gazed at the new picture - a sign that they remembered the familiar picture and were interested in the new object.

The test was a good way to measure the potential effects of fish intake, Oken said, because it looked at both brain function and vision; omega-3 fatty acids were also essential in eye development.

- REUTERS