Abstract
Background
The role of vitamin D on muscle health is debated.
Methods
An individual participant metanalysis of four randomized placebo-controlled trials, investigating short term (three to nine months) effects of vitamin D3 in moderate (2800 IU) to high (7000 IU) daily oral doses on muscle health and quality of life (QoL). Inclusion criteria were either obesity (N=52), newly diagnosed primary hyperparathyroidism (N=41), Graves’ disease (N=86) or secondary hyperparathyroidism (N=81).
Results
Overall (N=260) as well as in a subgroup analysis including only vitamin D insufficient (25(OH)D< 50 nmol/L) individuals (N=176), vitamin D supplementation did not affect measures of muscle health (isometric muscle strength, Timed Up and Go test, Chair Rising Test, body composition, and balance) or QoL. However, a beneficial effect was present on QoL (physical component score) in vitamin D deficient (25(OH)D≤ 25 nmol/L) individuals (N=34).
Overall, relative changes in 25(OH)D inversely affected maximum muscle strength in a dose response manner. Stratified into BMI </≥ 30 kg/m 2, vitamin D supplementation had divergent effects on isometric muscle strength, with beneficial effects in obese individuals (N=93) at knee flexion 90° (p=0.04), and adverse effects in non-obese individuals (N=167) at handgrip (p=0.02), knee extension 60° (p=0.03) and knee flexion 60° (p<0.01).
Conclusion
Overall, short-term treatment with moderate to high daily doses of vitamin D did not affect muscle health or QoL. A potential beneficial effect was present on muscle strength in severe obese individuals and on QoL in vitamin D deficient individuals. Subgroup analyses however suggested negative effects of large relative increases in p-25(OH)D.