Vitamin D Supplementation May Enhance Athletic Performance

Research suggests that vitamin D supplementation may boost skeletal muscle function and enhance athletic performance.

Vitamin D may play a key role in athletic performance, according to a team of researchers from the University of Ulster in Northern Ireland who conducted a review of publications concerning vitamin D status and sports. Their review, published electronically in the journal Sports Medicine, is a comprehensive description of studies of athletes across a range of sports.

The authors report that athletes may be predisposed to vitamin D deficiency, with studies reporting a high prevalence of athletes with low vitamin D concentrations (<50 nmol/L). Athletes at greatest risk are those who train indoors, train very early or late in the day, or who wear equipment that prevents sunlight exposure. Some reports indicate the deficiency is greatest during the winter. Interestingly, a high proportion of athletes from equatorial countries present with low vitamin D concentrations, perhaps because they often train indoors to escape blistering heat.

The authors also review the specific roles of vitamin D that are critical for athletes. These include bone formation (vitamin D enhances calcium absorption at the small intestine, but requires levels >50 nmol/mL) and immune health. The latter is important to athletes because while moderate exercise enhances immune function, strenuous exercise challenges the human immune system.

Additionally, vitamin D deficiency has an indirect effect on cardiovascular and respiratory health via its role in muscle strength and its propensity to cause secondary hyperparathyroidism, a condition that cascades into cardiac pathology. In the lung, it appears that vitamin D is critical to healthy surfactant.

Some of vitamin D’s effects seem to be more pronounced in the young or the older athlete. In children, most bone growth occurs before the late adolescent period, so vitamin D levels are very important. Older athletes may be more prone to cardiac complications.

The authors indicate that vitamin D supplementation may also enhance skeletal muscle function and athletic performance, although its exact mechanism of action is still unclear. More studies are needed to identify vitamin D’s extraskeletal effects in particular. Clinicians should aim for maintenance-level 25(OH)D concentrations above 80 nmol/L for athletes in their care.