A maternal diet rich in methyl donors, of which one source is the prenatal supplement folate, can increase developing fetus' chances of suffering from asthma after birth.
John Hollingsworth and colleagues, at Duke University Medical Center, Durham, have generated the evidence in mice.
In the study, the development and severity of allergic airway disease (the experimental equivalent of asthma) was found to be enhanced in mice born to mothers who had eaten a diet supplemented with methyl donors.
Further analysis indicated that some genes in the mice exposed to methyl donors in utero were modified by methylation in a different way to mice not exposed to methyl donors in utero.
This change in the pattern of methylation, altered the expression of the genes and is likely to be the underlying cause of the increased development and severity of allergic airway disease.
Both the authors and, in an accompanying commentary, Rachel Miller, at
Columbia University College of Physicians and Surgeons, New York, discuss the potential implications of this study in light of the fact that folate is a source of methyl donors and is an important prenatal supplement that helps prevent congential abnormalities.
As they caution, it is important to determine if the same effects occur in humans before changing the current recommendations about prenatal supplementation.