Vitamin D supplementation and asthma control
Recent evidence suggests that supplementation with Vitamin D3 in asthmatic adults who are deficient or have insufficient levels of vitamin D may result in better asthma control (1).
The research, published in Thorax, suggests that vitamin D levels should be monitored in asthmatic patients and deficiencies corrected (1).
The relationship between asthma and vitamin D deficiency has been known for some time. Several studies in adults and children indicate that low vitamin D levels are associated with poorer asthma control, poorer lung function, decreased response to glucocorticoids and more frequent exacerbations (2,3,4,5,6,7). However, interventional studies conducted in this regard have shown conflicting results. A Cochrane review of vitamin D and asthma trials concluded that vitamin D reduced the risk of asthma exacerbation however, more data is needed relating to difference in effect between adults and children and with respect to asthma severity, baseline vitamin D status and doses (8).
This trial included 112 adults with asthma and serum 25-hydroxyvitamin-D3 levels below 74.9 nmol/L (reference range 50 – 140 nmol/L). Participants were randomised to receive either oral supplements with 16,000 IU of calcifediol (25-hydroxyvitamin D3) per week or a placebo, in addition to usual asthma treatment. Scores on the asthma control test (ACT) were used to measure the effects of supplementation. At baseline, mean ACT scores were 17.71 in the intervention group and 19.02 in the control group. After six months, mean ACT scores were 20.49 in the intervention group and 18.23 in the control group. There was also a significant improvement seen in quality of life in the intervention group compared to the control group.
The current study has several limitations, including the small number of participants, a short follow up period and reliance on self-administered questionnaires and recall bias. Nevertheless, the research indicates that monitoring for, and correcting vitamin D deficiency can decrease inflammation and improve response to treatment with inhaled corticosteroids thereby improving asthma control. Trials with larger sample sizes and longer follow-up period are required to determine if there are subpopulations of asthmatic patients that would benefit most from vitamin D supplementation, and to establish adequate supplementation guidelines.
