Effects of daily vitamin D supplementation on respiratory muscle strength and physical performance in vitamin D-deficient COPD patients: a pilot trial

Abstract

Background

Although vitamin D is well known for its function in calcium homeostasis and bone mineralization, several studies have shown positive effects on muscle strength and physical function. In addition, vitamin D has been associated with pulmonary function and the incidence of airway infections. As vitamin D deficiency is highly prevalent in chronic obstructive pulmonary disease (COPD) patients, supplementation might have a beneficial effect in these patients.

Objective

To assess the effect of vitamin D supplementation on respiratory muscle strength and physical performance in vitamin D-deficient COPD patients. Secondary outcomes are pulmonary function, handgrip strength, exacerbation rate, and quality of life.

Methods

We performed a randomized, double-blind, placebo-controlled pilot trial. Participants were randomly allocated to receive 1,200 IU vitamin D3 per day (n=24) or placebo (n=26) during 6 months. Study visits were conducted at baseline, and at 3 and 6 months after randomization. During the visits, blood was collected, respiratory muscle strength was measured (maximum inspiratory and expiratory pressure), physical performance and 6-minute walking tests were performed, and handgrip strength and pulmonary function were assessed. In addition, participants kept a diary card in which they registered respiratory symptoms.

Results

At baseline, the mean (standard deviation [SD]) serum 25-hydroxyvitamin D (25(OH)D) concentration (nmol/L) was 42.3 (15.2) in the vitamin D group and 40.6 (17.0) in the placebo group. Participants with vitamin D supplementation had a larger increase in serum 25(OH)D compared to the placebo group after 6 months (mean difference (SD): +52.8 (29.8) vs +12.3 (25.1), P<0.001). Primary outcomes, respiratory muscle strength and physical performance, did not differ between the groups after 6 months. In addition, no differences were found in the 6-minute walking test results, handgrip strength, pulmonary function, exacerbation rate, or quality of life.

Conclusion

Vitamin D supplementation did not affect (respiratory) muscle strength or physical performance in this pilot trial in vitamin D-deficient COPD patients.

Keywords:

• chronic obstructive pulmonary disease
• vitamin D
• physical performance
• muscle strength
• pulmonary function

Supplementary materials

Table S1 Differences (Δ) after 6 months with exclusion of participants using vitamin D supplements

Table S2 Differences (Δ) after 3 months

Author contributions

All authors have made substantial contributions to the conception and design of this study. All were equally involved in drafting the manuscript or revising it critically and have given final approval of the version to be published.

Disclosure

The authors report no conflicts of interest in this work.