In addition, the study showed that people with low vitamin D levels didn’t respond as well to asthma treatments compared to people with higher vitamin D levels.
"Our findings suggest that vitamin D levels influence a number of important features of asthma, including lung function, bronchospasm, and therapeutic response to steroids,” researcher E. Rand Sutherland, MD, MPH, chief of the pulmonary division at National Jewish Health in Denver, says in a news release. “The next question to answer is whether giving supplemental vitamin D will lead to clinical improvements in patients with asthma."
Vitamin D is most commonly produced by the skin in response to exposure to sunlight and is also found in some foods.
Vitamin D Tied to Asthma Severity
In the study, published in American Journal of Respiratory and Critical Care Medicine, researchers compared vitamin D levels and asthma severity in 54 people with asthma.
The results showed that people with higher vitamin D levels had better lung function measures than people with lower vitamin D levels. In particular, people with low vitamin D performed worse on tests of lung function and airway hyper-responsiveness, two hallmarks of asthma.
Researchers say vitamin D levels were directly related to the participants’ score on the breathing tests: the lower the vitamin D levels, the worse their performance.
For example, airway hyper-responsiveness was nearly twice as bad in people with vitamin D insufficiency (below the threshold level of 30 nanograms/milliliter) as in those with higher vitamin D levels.
The study also showed that low vitamin D levels were associated with increased production of a pro-inflammatory protein in the blood, which raises the possibility that low vitamin D levels could be related to increased inflammation in people with asthma.