Dr. Hiroshi Tachimoto and colleagues in Japan recently conducted a 2 month randomized controlled trial of 800 IU/day of vitamin D for two months in 89 children with asthma who averaged 10 years of age.
Tachimoto H, Mezawa H, Segawa T, Akiyama N, Ida H, Urashima M. Improved Control of Childhood Asthma with Low-Dose, Short-Term Vitamin D Supplementation: A Randomized, Double-Blind, Placebo-Controlled Trial. Allergy. 2016 Feb 3. doi: 10.1111/all.12856. [Epub ahead of print]
Interestingly, baseline levels of 25(OH)D averaged about 28 ng/ml in both groups. After two months of supplementation, the vitamin D status of the treatment group only improved to 32 ng/ml, while the placebo group remained unchanged.
They used multiple clinical assessments to measure asthma severity with an intention to treat analysis. At 2 months, the Global Initiative for Asthma (GINA) was significantly more improved in the vitamin D group compared with the placebo group (P=0.015). Childhood asthma control test (CACT) scores, a secondary outcome, were also significantly improved in the vitamin D group compared with the placebo group at 2 months (P=0.004), and differences remained significant at 6 months (P=0.012).
The proportion of patients with a peak expiratory flow rate <80% were significantly less in the vitamin D group (15%) than the placebo group (34%) at 6 months (P=0.032). No other changes in pulmonary function tests were noted. No significant side effects were noted with treatment.
Interestingly, the authors purposely used a relatively low dose of vitamin D, 800 IU/day. However, in a previous trial on influenza, the authors used 1,200 IU/day and noticed a dramatic reduction in asthmatic complications.
We think asthmatic children should obtain natural vitamin D levels, defined by the levels of modern day hunter-gatherers in equatorial Africa, as those levels best represent the vitamin D level we evolved with.
Therefore, asthmatic children should receive safe, sensible sun exposure when their shadow is shorter than they are as frequently as possible in the spring and summer but take supplements during the fall and winter.
How much vitamin D the asthmatic children should take via supplement depends on their baseline blood levels. Remember, the Vitamin D Council sells the least expensive in-home vitamin D test kit on the market, and we use Heartland Assays to run the tests, which is the company owned by Dr. Ronald Horst and Professor Bruce Hollis, both world class experts in vitamin D testing.