A new study suggests mothers who routinely eat nuts or nut products during pregnancy may be unwittingly increasing the chances of their child going on to develop asthma.
Researchers at Utrecht University in the Netherlands tracked the eating habits of over 4,000 pregnant women during the final month of their pregnancies. They asked the women to record how often they ate vegetables, fresh fruit, fish, eggs, milk, milk products, nuts and nut products. Many of the foods in these food groups are known to be common allergens.
The researchers were able to maintain contact with 2832 of the mothers after they gave birth and went on to collect data on their children. Each child was followed from birth to age 8. Their diets were monitored and special attention given to any allergies or symptoms of asthma that might have developed.
This Dutch study is the first to record the mother's diet while they were pregnant rather than relying on memory years later. It is also the first to track the incidence of asthma in children past the first 5 years of their lives. The results of the study are published in the latest issue of the American Journal of Respiratory and Critical Care Medicine.
The results suggest that children whose mothers reported eating nuts on a daily basis were 40-60% more likely to develop wheezing or other asthma-related symptoms compared to children whose mothers rarely ate nuts and/or nut products (fewer than three times a month or never).
In a statement study author Saskia Willers said, "We were pretty surprised to see the adverse associations between daily versus rare nut product during pregnancy and symptoms of asthma in children because we haven't seen this in similar previous studies."
The research also confirmed the results of previous studies showing that children are more likely to develop asthma and allergies if their mother also suffers from these conditions.
The results of this latest study may lend weight to the idea that what a mother eats during pregnancy has an effect on the future health of her child. Previously, a British study in the 1990s found an association between the consumption of peanuts during pregnancy and negative health effects which prompted the government to advise pregnant women to avoid the legume.
However, the results of the latest Dutch study are not considered definitive proof that eating nuts during pregnancy actually causes asthma in the mother's offspring. Instead the results are seen as pointing out an association which requires further study.
The study is seen as good quality research as large numbers of participants were used and dietary habits were constantly recorded rather than relying on memory later. However, other factors such as genetics and other things the mothers did during pregnancy such as taking medications or nutritional supplements were not taken into account.
Experts believe that dietary habits probably and other environmental factors interact with genetic predisposition in a complex way to ultimately determine whether a child will develop asthma or allergies.
Other recent studies have linked traffic pollution and asthma in children.