Eating fish and apples during pregnancy protects children against asthma and allergic diseases, a new study suggests.

The study, conducted at the University of Aberdeen, UK, found that the children of mothers who ate the most apples were less likely to ever have wheezed or have doctor-confirmed asthma at the age of 5 years, compared to children of mothers who had the lowest apple consumption.

Children of mothers who ate fish once or more a week were less likely to have had eczema than children of mothers who never ate fish, says the study which was presented at the American Thoracic Society 2007 International Conference yesterday.

The study did not find any protective effect 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 researchers studied 1212 children born to women who had filled out food questionnaires during their pregnancy.

When the children were 5 years old, the mothers filled out a questionnaire about the children's respiratory symptoms and allergies, as well as a questionnaire about their child's food consumption.

The children were also given lung function and allergy tests. Previous studies in the same children have found evidence for protective effects of vitamin E and D and zinc during pregnancy in reducing the risk of children's wheeze and asthma, notes researcher Saskia Willers, M.Sc. of Utrecht University in the Netherlands.

If the new results are confirmed, she says, "Recommendations on dietary modification during pregnancy may help to prevent childhood asthma and allergy."

Willers concludes that at least until age 5, a mother's diet during pregnancy might be more influential on a child's respiratory health than the child's own diet. She notes that further study of this group of children will be needed to see whether the association with the mothers' diet declines in older children, and if mothers' and their children's diets interact in older children.

Willers suggests that the beneficial effect of apples may come from powerful antioxidants called flavonoids, while fish's protective effect may come from omega-3 fatty acids, which other studies have suggested have a protective effect on the heart and may have a protective effect in asthma.

"Other studies have looked at individual nutrients' effect on asthma in pregnancy, but our study looked at specific foods during pregnancy and the subsequent development of childhood asthma and allergies, which is quite new," Willers says.

"Foods contain mixtures of nutrients that may contribute more than the sum of their parts," it added.