Diet and Asthma: Are They Related?

Asthma is a common chronic inflammatory disease of the airways that affects more and more Americans each year. Researchers are curious to find out whether our evolving dietary habits have played a role in the increase in incidence of asthma, and whether changing the components of our diet could help prevent or control asthma.

Antioxidants

According to a 2009 review and meta-analysis, researchers from the University of Nottingham in the UK concluded that dietary antioxidant Vitamin A and C intakes and blood Vitamin C levels were significantly lower in adults and children with asthma, especially in those with severe asthma. Vitamin E intake was significantly lower in people with severe asthma but was unrelated to asthma status. However, when researchers supplemented the diets of asthmatics with Vitamin C, selenium, and Vitamin A, they failed to demonstrate any improvements.

Polyunsaturated Fatty Acids (Omega-3 and Omega-6 Fats)

Researchers suspect that our decreasing intake of omega-3 fats and increasing intake of omega-6 fats has contributed to the increase in allergic diseases and asthma. A review published in the Journal of the American Dietetic Association in January 2011 concluded that fish intake (a source of omega-3 fats) is associated with a lower risk of asthma in both adults and children, while margarine intake (a source of omega-6 fats) in the form of spreads or cooking oil is associated with more asthma in adults, as well as a higher risk of asthma and wheezing in children. When they supplemented diets with omega-3 fats in the form of fish oil capsules, the researchers did not find convincing evidence that it helped with asthma control. However, in 2009, a group of Egyptian researchers reported that omega-3 fats, Vitamin C, and zinc supplementation of asthmatic children, either individually or in combination, improved asthma control, lung function, and inflammatory markers.

Vitamin D

In a few large trials, low serum Vitamin D has been shown to correlate with reduced lung function in adults and increased asthma severity in children. The effectiveness of supplemental Vitamin D in established asthma is currently unknown, but we should expect to get some clarifications after the ongoing trials results are released.

Maternal Diet

Many studies have reported association of the mother’s diet during pregnancy with the development of childhood asthma in the offspring. For example, a low intake of Vitamin D, Vitamin E, and zinc by mom during pregnancy is linked to an increased likelihood of childhood wheezing and asthma. However, the interaction between nutrients in the mother’s diet and fetal development is very complex and still poorly understood. It remains to be proven whether changing the mother’s diet during pregnancy can help reduce the prevalence of asthma in her children.

The Bottom Line

Although we have seen a link between certain nutrients and asthma, it appears that changing the diet has very little effect on established asthma. The studies to date are mostly preliminary and observational, and until we see more concrete evidence, there is no immediate need to rush to the supplements aisle and start popping pills.

Owennie Lee, RD

Alumni: University of British Columbia – Owennie is a registered dietitian with a soft spot for chocolate and coffee. She is a believer in balance and moderation, and is committed to keeping healthy eating enjoyable and fun. Owennie received her dietetics training in Vancouver, and is a member of Dietitians of Canada and the College of Dietitians of British Columbia. She has experience in a wide variety of settings, such as clinical nutrition, long-term care and outpatient counseling. Owennie has also worked for a community nutrition hotline and participated regularly as a guest radio host, where she enjoyed sharing her passion and knowledge about food and nutrition with people.