The importance of vitamin D for bone health is now well-recognized, and the epidemic of vitamin D insufficiency and deficiency is thought to contribute to a wide range of medical conditions including cancers, mood disorders, autoimmune conditions, cardiovascular disease and more.1 As such, vitamin D sufficiency (25(OH)D greater than 30 ng/ml) is associated with a reduced risk of death from all causes.2,3
In addition to bone, vitamin D receptors are present in almost all cells of the body, including muscle cells. Vitamin D’s primary function is the regulation of calcium transport and metabolism – since calcium transport is an integral part of muscle contraction and relaxation, vitamin D is extremely important for proper muscle function. There is also evidence that achieving vitamin D sufficiency may help to increase muscle mass. In the early 20th century, observations led athletes and trainers to believe that sunlight exposure could enhance athletic performance. Athletic performance has been reported to vary seasonally, peaking in the summer; positive effects of UVB exposure on athletic performance were reported as early as the 1930s. There is now speculation that improved vitamin D status is the reason for these findings.4,5
Previous studies have shown that vitamin D status correlates with muscle function in the elderly, and that vitamin D supplementation improves muscle strength in elderly and/or deficient populations.6-9 New research is beginning to extend these findings to physical performance in athletes. Since there is a high prevalence of vitamin D insufficiency overall, and vitamin d is crucial for bone and muscle function, does vitamin D status affect injury rates or performance in athletes? Two recent studies on professional ballet dancers suggest that it does.
Indoor athletes are likely to have insufficient vitamin D levels.5,10 The first study showed that this was true of ballet dancers in a UK company; on average, their vitamin D status was insufficient (<30 ng/ml) all year round and varied seasonally. In the winter, dancers averaged 14.9 ng/ml (deficient), and in the summer, 23.9 ng/ml (insufficient). The authors also observed a greater occurrence of injuries in the winter months.11 The follow-up study provided vitamin D3 supplements (2000 IU/day) to some of the dancers during the winter, and investigated muscle function and injury rates. In the vitamin D group, there were increases in isometric strength and vertical jump height, plus significantly fewer injuries compared to the control group.12
This is consistent with a previous study of UK athletes, which compared 5000 IU vitamin D for 8 weeks to placebo. The researchers saw increases in sprint times and vertical jump height in the vitamin D group, but not in the placebo group.13
These results suggest that vitamin D’s beneficial effects on bone and muscle physiology can translate into enhanced athletic performance. Achieving sufficient blood vitamin D levels (25(OH)D of 30-45 ng/ml) is crucial for the health of the entire body, not just for preventing osteoporosis.
Image credit: Flickr - TooFarNorth
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