Levels of vitamin E in women during pregnancy are inversely associated with the risk of asthma in their children, according to a report in the American Journal of Respiratory and Critical Care Medicine.
However, in an interview Dr. Graham Devereux emphasized that "the message for pregnant women isn't to go out and stock up on vitamin E." He explained that the use of vitamin E supplements during pregnancy is controversial with many studies suggesting no benefit and possibly even a harmful effect.
As such, the current findings have no immediate implications for treatment, but hopefully will lead to studies that could provide definitive answers, Dr. Devereux, from the University of Aberdeen in the UK, noted. For now, "pregnant women should just be encouraged to eat a healthy diet."
In an earlier analysis of the study group, the researchers found an inverse association between maternal vitamin E levels during pregnancy and the risk of wheezing in 2-year-old children. In the present analysis, asthma-related outcomes of 1,861 children in the earlier study were assessed when they reached 5 years of age.
Food frequency questionnaires and blood tests were performed to assess the mothers' nutrient status, the report indicates. Respiratory questionnaires, imaging and skin-prick tests were used to evaluate the presence of asthma in the children.
The researchers found the low maternal vitamin E levels were associated with having a child with asthma, persistent wheeze, wheezing or asthma during the previous year, or ever having a diagnosis of asthma, the authors note. The inverse relationship was also seen, with high maternal vitamin E levels being associated with a lower risk of having a child with asthma or related symptoms.
The researchers also found a negative association between maternal zinc levels and children with active asthma or those who had ever been diagnosed with asthma.
By contrast, a child's nutrient status was not linked to respiratory outcomes, the report shows.
As to how low maternal vitamin E may raise the risk of childhood asthma, Dr. Devereux offered two possibilities. First, animal research has suggested that a deficiency of vitamin E in the womb leads to impaired lung development. Second, low vitamin E levels might adversely affect the immune system, resulting in a more asthma-prone environment.
SOURCE: American Journal of Respiratory and Critical Care Medicine, September 2006.
