"There is a potential that restoring normal vitamin D levels in people with asthma may help improve their asthma," Sutherland said.
But whether vitamin D supplements will help asthmatics isn't known, he added.
Current recommendations for vitamin D supplements for adults is 400 IU to 600 IU, depending on age, according to the U.S. National Institutes of Health.
"There is likely little harm in adhering to those guidelines," Sutherland said.
The Institute of Medicine is currently evaluating these levels and expects to announce new guidelines in May.
Sunlight, fatty fish and fish oils are also sources of vitamin D.
Dr. Michael F. Holick, director of the Vitamin D, Skin and Bone Research Laboratory at Boston University School of Medicine, called this "a very nice study that confirms previous observations that vitamin D enhances lung function."
"It is also known that glucocorticoids [steroids] increase the destruction of vitamin D, thus making patients with asthma at higher risk for vitamin D deficiency, which in turn decreases lung function and makes their disease worse," he said.
Holick thinks most people, asthmatic or not, get too little D and should take supplements.
"It's pretty clear that you need a minimum of 1,400 and up to 2,000 IU a day, and if you are obese, you probably need at least one and a half to two times as much, because the fat sequesters the vitamin D," Holick said. "We now recognize that you can take up to 10,000 IUs a day and not worry about any untoward toxicity."
For more information on asthma, visit the U.S. National Institutes of Health.
SOURCES: E. R
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