Vitamin D supplementation does not improve leg muscle strength and performance in older adults

1. In this randomized controlled trial, vitamin D supplementation was not associated with change in leg power, strength, or physical performance in older adults with vitamin D deficiency.

2. Furthermore, vitamin D supplementation did not significantly change muscle fiber composition in leg muscle biopsies from older adults compared to controls.

Evidence Rating Level: 1 (Excellent)

In the aging population, loss in muscle strength and performance is highly prevalent and is associated with adverse clinical outcomes. Although vitamin D deficiency is also prevalent in this population, it is unclear whether vitamin D supplementation could improve muscle strength and performance. Therefore, the purpose of the present study was to examine the effect of daily vitamin D supplementation on muscle strength and power in older adults.

This randomized controlled trial included 136 low-functioning adult patients aged 65-89 years living in North Carolina. Patients were included if they were not taking vitamin D supplementation, had vitamin D levels between 18 to <30ng/mL, and had some mobility difficulties. Participants who were dependent on a walker, had a body mass index (BMI) >40 kg/m2, or had insulin-dependent diabetes, heart failure, lung disease, or other chronic conditions were excluded. The participants were randomized 1:1 to either 2000 IU/day of vitamin D3 or placebo for 12 months. The primary outcome was leg power assessed using the Nottingham Power Rig. Secondary outcomes included leg strength and physical performance, as measured by Short Physical Performance Battery (SPPB) score, timed up and go (TUG) test, postural sway, and gait velocity. Outcomes were evaluated at baseline, 4 months, and 12 months. A subset of 38 participants were randomly selected to undergo leg muscle biopsy at baseline and 4-months.

The results demonstrated that there was no difference in leg power, strength, SPPB score, TUG, postural sway, or gait velocity in participants treated with vitamin D supplementation compared to the control group. There were also no observable differences between the muscle biopsies of those in the treatment and control groups with regards to muscle fiber composition. However, this study was limited by its lack of generalizability to older adults who are not low-functioning or those without vitamin D deficiency. Nonetheless, the study comprehensively examined the impact of vitamin D supplementation on outcomes in older adults.

Click to read the study in The American Journal of Clinical Nutrition

Image: PD

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