Writing in Nutrients, researchers from Harvard Medical School, University of Cambridge, University of Otago and University of Auckland, said the benefits of vitamin D was “striking” in asthmatic and COPD patients with serum vitamin D at lower than 25nmol/L.
Unexpectedly, the researchers also observed that female patients who took high dose of vitamin D had 46% higher risk of the condition turning for the worse and had to take oral corticosteroid.
“Among women, the vitamin D group had worse lung function,” the researchers highlighted, although they believe that the results were most likely due to chance and urged for further research.
Over 5,200 people took part in this RCT, where they were randomised to take either a soft gel capsule containing 100,000 IU of vitamin D or placebo for about 3.3 years.
The subjects had to take two capsules of either vitamin D or placebo in the first month and one capsule monthly from the second month onwards.
From here, the researchers conducted a subgroup analysis on older adults with asthma or chronic obstructive pulmonary disease (COPD). The purpose was to find out the effects of vitamin D on their conditions.
In total, 775 subjects were analysed, with 214 suffering from asthma, 356 suffering from COPD, and 205 suffering from both conditions.
Amongst the intervention group, their serum level of vitamin D had increased from about 63nmol/L to 135 nmol/L, while that of the placebo group did not change.
Despite the increase in serum vitamin D levels, the intervention group did experience a lower incidence rate of oral corticosteroid prescription to curb their asthmatic or combined asthma/COPD symptoms.
Amongst the intervention group, the incidence rate of oral corticosteroid prescription for asthma was 0.49, higher than the placebo group at 0.47.
Their incidence rate of oral corticosteroid prescription for asthma and COPD combined was 0.59, again, higher than the placebo group at 0.48.
Vitamin D supplementation was useful only in subjects with low vitamin D levels at baseline, the researchers pointed out.
Amongst subjects with serum vitamin D at a baseline level of less than 25nmol/L, vitamin D supplementation had exerted a “protective effect” as seen in the lower incidence rate of oral corticosteroid prescription.
In this group of subjects, those from the intervention group recorded an incidence rate of 0.07, which was 10 times lower than that of the placebo group at 0.70.
Whereas in subjects with baseline vitamin D of 25 to 49.9 nmol/L, the incidence rate was 0.57 in the intervention group, higher than 0.42 seen in the placebo.
These findings were consistent with previous meta-analyses on vitamin D’s effects on asthma and COPD, the researchers said.
“In summary, although monthly high-dose vitamin D supplementation had no overall impact on exacerbations of asthma or COPD in these older adults, we found evidence of probable benefit among those with severe vitamin D deficiency,” they concluded.
The research was funded by the Health Research Council of New Zealand and the Accident Compensation Corporation of New Zealand.
Effect of Monthly Vitamin D Supplementation on Preventing Exacerbations of Asthma or Chronic Obstructive Pulmonary Disease in Older Adults: Post Hoc Analysis of a Randomized Controlled Trial
Authors: Carolos A. Camargo, Jr and et al