Low vitamin D and athletes

Athletes put higher demands on their bodies than other people. Problems with low vitamin D status will disproportionately impact athletes because of the role vitamin D plays in preserving bone, muscle, and immune function. While you might suspect that athletes training outdoors would have higher vitamin D levels than others, recent studies have reported surprising deficits, even for athletes training outside (1,2). This article outlines how low vitamin D status can impact athletes more seriously rest of the population.

Low vitamin D: how it impacts the muscles
Vitamin D has an unappreciated role in the promoting muscle function and strength. A Dutch study on aging found that hand grip strength test scores were associated with low levels of vitamin D (3). This finding fits into an emerging picture of the hormonal role of vitamin D in promoting muscular integrity alongside bone integrity (4).

Getting sore after bouts of athletic training is an experience many are familiar with. On a molecular level, soreness results from upregulation of inflammatory molecules called cytokines. Vitamin D reduces the production of a number of these cytokines (2). On a more extreme note, overtraining syndrome results from prolonged cytokine elevation (5). While an explicit link to low vitamin D status has not been established, I expect that a parallel exists here.

Low vitamin D: skeletal impact
A major concern among athletes is both acute and chronic (or stress) fractures. A study of Finnish military recruits found that low vitamin D status was statistically associated with stress fracture risk (6). Bischoff-Ferrari also found strong association between vitamin D deficiency and bone fracture risk (7). While low serum levels of vitamin D have been associated with musculoskeletal pain, this finding is still controversial (8,9)

Getting Ill
Intense training has been shown to lower innate immunity systems in athletes (10). As a result, risk of upper respiratory tract infections, and probably other forms of illness, increases during stressful training. Vitamin D strengthens the body's innate immune defenses , which can allow athletes to compensate for the challenges associated with heavy training.

The bottom line?
The bottom line here is that athletes put their muscles, joints, and immune systems under more intense stress during the course of normal training than most non-athletes do. Vitamin D is one of the best ways to combat stress in the body, boosting the immune system, and strengthening the muscles and skeleton. Vitamin D supplementation represents a good possibility for avoiding a number of related to overtraining and chronic stress.

Signs of low vitamin D status

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10. Nieman, DC. "Special feature for the Olympics: effects of exercise on the immune system: exercise effects on immunity." Immunol Cell Biol. 78 (2000) 496-501.