ORLANDO, FLA. — The type of fish a woman consumes during pregnancy may affect the risk of her child developing asthma, Frank D. Gilliland, M.D., said at the 100th International Conference of the American Thoracic Society.
“We found maternal oily-fish intake was strongly protective in mothers who had a family history of asthma,” Dr. Gilliland, of the department of preventive medicine at the University of Southern California, Los Angeles said during a press conference at the meeting. The children “had a 70% reduction in their risk of asthma, and this was not observed in children with no family history.”
Oily fish, which are rich in omega-3 fatty acids, include yellowtail and cold-water fish like salmon, trout, and orange roughy. Eating oily fish on a regular basis a few times a month seemed sufficient to confer benefit, and the more oily fish a pregnant woman ate, the lower the risk of asthma in her child.
Using data from the Children's Health Study, a population-based study of school-aged children in 12 Southern California communities, Dr. Gilliland and associates conducted a nested, countermatched, case-control study to evaluate whether maternal fish consumption affected their children's asthma risk. Cases included those of children diagnosed with asthma by age 5; asthma-free children served as controls. The researchers completed telephone interviews with the children's mothers, collecting dietary and environmental exposure information.
Last year the Food and Drug Administration issued a consumer advisory about methylmercury in fish and shellfish. The advisory recommends that pregnant women strictly avoid fish that are high in mercury, and limit consumption of fish that are low in mercury, like salmon, to 12 ounces per week. Nearly all fish and shellfish contain trace amounts of mercury, but swordfish, shark, and other large fish tend to have greater amounts of the neurotoxin. Women could follow the FDA guidelines and still obtain the asthma-protective effect seen in this study. Favorable results were observed in women who ate as few as two servings of oily fish per month.
Dr. Gilliland suggested that omega-3's anti-inflammatory properties might reduce the child's asthma risk by decreasing inflammation in the developing fetus. “Some data suggest maternal omega-3 fatty-acid intake alters the immune phenotype of the fetus at birth,” Dr. Gilliland said.
The results did not hold when women consumed canned or non-oily fish during pregnancy.