Vitamin D May Help Relieve Asthma
October 19, 2010
For years, medical experts have speculated that asthma may be linked to a deficiency of vitamin D. Though debate continues over how much vitamin D is enough, experts now believe they have uncovered an association between asthma and low levels of the "sunshine vitamin," so called because our bodies can manufacture vitamin D when exposed to sunlight.
To better understand the relationship between vitamin D and asthma, researchers combed through asthma-related scientific articles published between 1950 and 2009. They discovered that asthma is more common among people with obesity, African Americans and people living in Westernized countriesthe same groups that also have higher rates of vitamin D deficiency.
Writing in the Annals of Allergy, Asthma & Immunology, the researchers also noted the roles that vitamin D seems to play in the functioning of bronchial smooth muscle cells, lung epithelial cells, and the immune system's response to allergens and viral infections. All of these are related to exacerbation of asthma symptoms.
Despite these findings, no one can say for sure if there's a cause-and-effect relationship between deficiencies of vitamin D and asthma. For one thing, there's no agreement at this point on what constitutes vitamin D deficiency, or how levels of the vitamin should vary seasonally. A person who has low levels of the vitamin in March may have sufficient levels in May because of sun exposure, but few studies have taken these seasonal variations into account.
And the suggested level of vitamin D supplementation is a moving target: the recommended daily intake of vitamin D is 200 IU for children and adults younger than 50, 400 IU for adults 51 to 70, and 600 IU for those over 70 years of age. The Institute of Medicine is considering whether to raise the recommended daily intake of vitamin D; new advice may be issued as early as November 2010.
Though more study is needed to determine the exact nature of vitamin D's effect on asthma, if you have asthma you may want to talk to your doctor about getting a blood test to determine your vitamin D levels.
If your level of vitamin D is found to be low, there are some easy ways to increase it: some experts suggest getting 5 to 30 minutes of sunlight between 10 a.m. and 3 p.m. twice a week (although the American Academy of Dermatology advises wearing sunscreen whenever one is exposed to the sun), taking a vitamin D supplement, or consuming foods such as fortified milk, cereal, yogurt and orange juice; fatty fish (like salmon, herring and trout); and eggs.
Sources: Sandu, et al. "The Role of Vitamin D in Asthma." Annals of Allergy, Asthma & Immunology, Sept., 2010; and Vitamin D Factsheet, Office of Dietary Supplements.