Asthma-Inducing Diet

A Nice Treat by Wong Luisang, 1996. Artkey / Corbis

A pregnant mouse's diet can induce epigenetic changes that increase the risk her offspring will develop allergic asthma, according to researchers at Duke Medical Center and National Jewish Health, a hospital based in Denver.

The researchers found that pregnant mice that consumed diets high in methyl donors, such as folic acid, which are common in dietary supplements, had offspring with more severe allergic airway disease than offspring from mice that consumed diets low in methyl-containing foods. Their results appear in the Journal of Clinical Investigation.

The findings suggest that "the dramatic increase in asthma during the past two decades may be related in part to recent changes in dietary supplementation among women of childbearing age," says David Schwartz, senior author on the paper and a professor of medicine at National Jewish Health. The prevalence of asthma has nearly doubled in the past twenty-five years. Asthma currently affects about 11 percent of the U.S. population and accounts for $9.4 billion in direct health-care costs.

Epigenetics is the study of gene regulation. Researchers have found that a variety of environmental factors, including diet, tobacco smoke, and medications, can lead to modification of methyl groups binding to certain DNA molecules, which can result in modified expression of specific genes.

Although no changes occur in the mother's genetic code, epigenetic effects can be passed to offspring. Emerging research has indicated that epigenetic mechanisms can affect the development of the immune system, skewing it either toward or away from a predisposition to allergies.

In this study, the research team found that the mice's male offspring also transmitted a higher predisposition to allergic airway disease to their progeny. "These epigenetic changes may partially explain why it has been so difficult to definitively identify genes that contribute to asthma risk: The effect of genetic variations can be masked or further complicated by epigenetic changes," says study co-author John W. Hollingsworth, an assistant professor of medicine at Duke.

The finding is particularly interesting given that folic-acid supplements have long been recommended to mothers-to-be. In 1992 the U.S. Public Health Service recommended that all women of childbearing age consume 400 micrograms of folic acid daily to reduce the risk of children developing birth defects. In 1996 the U.S. Food and Drug Administration required that folic acid be added to specific flour, breads, and other grains to prevent birth defects.

Given the important role folic acid supplementation has played in prevention of birth defects, Schwartz and Hollingsworth say that further research is called for.