The effect of vitamin D supplementation on lower-extremity power and function in older adults: a randomized controlled trial

Abstract

The effect of vitamin D supplementation on muscle function in older adults has been tested in randomized trials with mixed results, which may be due to differences in the study participant characteristics, including baseline vitamin D status. The results of 2 meta-analyses of randomized trials suggested a beneficial effect of vitamin D supplementation on muscle function in older adults with low baseline serum 25-hydroxyvitamin D [25(OH)D]. We aimed to test the effect of 12 mo of vitamin D supplementation on lower-extremity power and function in older community-dwelling adults screened for low serum 25(OH)D. This was a single-center, double-blind, randomized, placebo-controlled trial that included 100 community-dwelling men and women ≥60 y old who had serum 25(OH)D ≤20 ng/mL at screening and a mean±SD serum 25(OH)D of 20.2±6.7 ng/mL at baseline. Participants were randomly assigned to 800 IU vitamin D3/d (intervention) or placebo. Those in the intervention group whose serum 25(OH)D was <28 ng/mL after 4 mo were given an additional 800 IU vitamin D3/d, whereas all other participants received placebo as an additional pill. After 12 mo, the mean±SD serum 25(OH)D was 32.5±5.1 ng/mL in the intervention group and 19.8±7.3 ng/mL in the control group (treatment × time P<0.001). The change in leg press power, function, and strength did not differ between the 2 groups over 12 mo (all treatment × time P≥0.60), nor did the change in lean mass (treatment × time P≥0.89). Increasing serum 25(OH)D to >32 ng/mL (on average) over 12 mo did not affect lower-extremity power, strength, or lean mass in older community-dwelling adults. This trial was registered at clinicaltrials.gov as NCT02293187.