Although monthly high-dose vitamin D supplementation appears to have no overall effect on exacerbations of asthma or chronic obstructive pulmonary disease (COPD), a probable benefit has been reported in patients with severe vitamin D deficiency (ie, baseline serum 25-hydroxyvitamin D [25OHD] levels of <25 nmol/L), according to study results published in Nutrients

Researchers conducted a post hoc analysis of data derived from a randomized, double-blinded, placebo-controlled trial among patients from Auckland, New Zealand. The investigators sought to examine whether supplementation with vitamin D can prevent exacerbations in older adults with asthma and/or COPD.

All of the study participants were randomly assigned to either an initial oral dose of 200,000 IU vitamin D3 followed by 100,000 IU monthly or to placebo, with an average follow-up period of 3.3 years. After baseline assessment, which included demographic status, lifestyle (ie, level of physical activity and smoking status), current intake of vitamin D supplements, past medical history, spirometry, and blood tests, the participants were mailed a run-in questionnaire with a masked placebo capsule.

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Upon return of the questionnaire within 4 weeks, a total of 5110 participants — 775 of whom had either asthma or COPD — were randomly assigned by the study statistician, stratified according to ethnic origin (Pacific Island, Maori, South Asian, European, or other) and 5-year age-groups, to receive identical-looking softgel capsules that contained either vitamin D3 100,000 IU or placebo.  All of the capsules were mailed monthly to the participants, with 2 capsules in the first letter (ie, an initial vitamin D3 200,000 IU bolus or placebo) and thereafter 1 capsule monthly (ie, vitamin D3

100,000 IU or placebo). During the follow-up period, which ended on July 31, 2015, there were 2 participants who withdrew from the placebo arm, leaving a total of 2558 participants who received vitamin D3 and 2550 who received placebo.

Asthma or COPD exacerbations were defined by the prescription of a short course of oral corticosteroids. The mean age of the study participants was 67 years; 56% were men. The mean baseline blood level of 25OHD was 63 nmol/L, with 2.3% of the participants having levels of <25 nmol/L and thus considered to have vitamin D deficiency.

Results of the study showed that overall, the use of vitamin D supplementation did not affect an individual’s risk for COPD or asthma exacerbation (hazard ratio [HR], 1.08; 95% CI, 0.84-1.39). Among participants with baseline 25OHD levels of <25 nmol/L, however, the values were significant (HR, 0.11; 95% CI, 0.02-0.51; P value for interaction =.001).

The researchers concluded that additional trials designed to examine the exact threshold (and mechanism) for the observed benefit are warranted, in which careful consideration is paid to the trial population being evaluated and the vitamin D dosing regimen being used. This will help to maximize the scientific yield of future analyses.


Camargo CA Jr, Toop L, Sluyter J, et al. 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. Nutrients. 2021;13(2):521. doi:10.3390/nu13020521