Eating Apples, Fish During Pregnancy Protects Kids From Allergies, Asthma

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"We were quite surprised to see a protective effect of apples, because, to our knowledge, no other study had seen that before," said Willers. "For fish, there is an earlier study that found a protective effect of maternal fish intake during pregnancy on childhood asthma."

No protective effect was found against asthma or allergic diseases from many other foods, including vegetables, fruit juice, citrus or kiwi fruit, whole grain products, fat from dairy products or margarine or other low-fat spreads.

The study speculated that apples may be beneficial because they contain flavonoids, which have been associated with a reduced risk of asthma in other studies, while fish's protective effect may be due to their omega-3 fatty acids.

"The authors' explanations are plausible," said Dr. Carlos Camargo, an associate professor of medicine and epidemiology at Harvard Medical School. "It's curious, however, why only apples would be protective, since flavonoids are present in other foods. This will require further work. The first step, however, is to see if other investigators find the same associations in other birth cohorts."

Dr. Augusto A. Litonjua, an assistant professor at Harvard Medical School, said this study adds to the growing literature that prenatal factors, specifically maternal diet during pregnancy, can affect the development of wheezing illnesses, asthma and allergies in young children.

It's too early, though, to recommend how much fish and apples pregnant women should eat, Willers said. Rather, it's important for them to follow a healthy, balanced diet.

Connie Diekman, director of university nutrition at Washington University in St. Louis, added that pregnant women should be careful about not eating too much fish because of the potential mercury and other pollutants in fish.

"The study supports the health benefits of increased fruits, vegetables and fish, but pregnant women need to exercise caution with king mackerel, tilefish, shark and swordfish, and should limit albacore tuna to 6 ounces per week," she said.

Litonjua added that in addition to a healthy diet, pregnant women should also take prenatal vitamins with folic acid and abstain from smoking and drinking to maximize the health of their growing fetus, and subsequently their young child.

More information

For more on allergies and asthma, visit the Asthma and Allergy Foundation of America.