Relevance of vitamin D in muscle health.

This review will summarize the impact of vitamin D deficiency on muscle health. Mechanistic evidence regarding the presence of the specific vitamin D receptor in muscle tissue and muscle biopsy abnormalities observed with deficiency will be reviewed, as well as molecular and non-molecular effects of vitamin D in muscle tissue. At the clinical level, the evidence from randomized controlled trials of vitamin D supplementation on functional improvement and fall reduction will be summarized. Further, the manuscript will discuss whether vitamin D effects on fall prevention modulate in part its benefit on fracture prevention and why fall prevention is essential in fracture prevention at higher age. Finally, trial and epidemiological data will be reviewed to assess desirable serum 25-hydroxyvitamin D levels for optimal muscle health.