Vitamin D and Sports Performance

by Clare Wood

Vitamin D is a pro-hormone that plays a vital role in maintaining calcium and phosphate balance in the body, optimizing bone mineralization and the functioning of our skeletal muscle. It is mainly produced in the skin from direct UVB sunlight rays, with a very small amount coming from naturally occurring and fortified food sources.

Vitamin D deficiency

The best indicator of vitamin D status is the concentration of 25-hydroxyvitamin D 25(OH)D in the blood.

There is also growing evidence to suggest that many athletes are Vitamin D insufficient, up to rates of 40%, as well as deficient athletes, with the worst case seen in in middle-eastern athletes. Generally there are seasonal differences with lower Vitamin D levels seen in winter, as well as in indoor trained athletes. This may be important for the training and performance of athletes. 

Athletes appear to have the same risk of vitamin D deficiency as non-athletes. Athletes who are at greater risk of deficiency include whose who:

Effect on Performance

It is likely that poor vitamin D status can affect an athlete’s health and ability to train.  One meta-analysis suggests that Vitamin D may improve physical performance, but results have been seen mostly in older individuals. There have also been some improvements in muscle performance and bone mineral density in vitamin D supplemented athletes, but mostly in participants with initial low status. Again researchers have not been able to show sporting improvements through vitamin D supplementation.

Supplementation

With the high prevalence of vitamin D deficiency and insufficiency in the general population as well as athletes, plus the potential health benefits of supplementation, improving vitamin D status seems warranted. The improvement of Vitamin D levels can be made using the following strategies:

Summary

There is enough evidence to suggest that deficiency and insufficiency are widespread in the general population, which includes a high prevalence in athletes. However, there is currently insufficient evidence to show that vitamin D supplementation can improve exercise performance. Therefore routine supplementation is not justified for all athletes, unless they are specifically at risk. Athletes presenting with stress fractures, musculoskeletal pain, frequent illness, plus idiopathic muscle weakness (heaviness in the legs), overtraining injury, or respiratory tract infections plus other risk factors such as low sun exposure during training, should be targeted for assessment by a qualified Physician or Sports Dietitian.

Selected References

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