Vitamin D in athletes: More than just bone health?

Vitamin D’s role in bone growth and maintenance is well known, however, additional roles discovered suggest it can also contribute to the overall health and recovery of a competitive athlete. Due to prolonged training exposure and high levels of physical activity, physiological demands for vitamin D are increased in the athlete population.

As research continues to emerge exposing the prevalence and risks of deficiency among top level athletes, it is imperative to address the evolution of vitamin D’s role, the need for standardized screening, and possible benefits of supplementation.

Vitamin D and immune function

Vitamin D has been found to play an important role in aspects of the immune system by supporting the expression of the immune response. An athlete’s exposure to intense physical activity can suppress their immune response, which places them at an increased risk for acute illnesses, such as upper respiratory infections (URTIs), common colds, and influenza.

Studies report that athletes with a vitamin D deficiency are more likely to experience episodes of acute illness and a higher severity of symptoms. Vitamin D supplementation in this population has been shown to significantly decrease URTI incidence during a competitive season.

Vitamin D and inflammation

Following physical activity, the inflammatory response is activated and results in sport-related inflammation and cell injury in athletes. Vitamin D works to control this inflammation by increasing the production of anti-inflammatory cytokines while also decreasing the production of their pro-inflammatory counterparts.

These pro-inflammatory cytokines are thought to be elevated with overtraining syndrome and other sport-related inflammatory states. Limited evidence exists that directly associates vitamin D supplementation or status to risk of sport-related inflammation and injury, however, current research in other inflammatory conditions trends toward a link between supplementation and decreased inflammatory makers.

Practical applications

Large variations in supplementation dosing and length in current evidence make practical applications difficult for clinicians to interpret. Additionally, differences in cut points for 25[OH]D can make identifying vitamin D status and deficiencies a guessing game. When considering a vitamin D screening and supplementation protocol, sports dietitians should ask themselves these questions:

1. Does your athlete train or compete mostly indoors?
2. Do you live in a climate with low sun exposure? Or is it during a time of year with low sun exposure?
3. Does your athlete have a darker skin complexion?*
4. Does your athlete have any additional risk factors that warrant exploring vitamin D status? (For example, amenorrhea, history of bone injury, insufficient dietary calcium, etc.)

If many of these factors are at play with your athletes, working with your interdisciplinary team to identify deficient athletes and discuss supplementation may ultimately benefit their overall health and recovery.

*Athletes with darker complexion often present with low serum 25[OH]D, which is explained by genetic differences in vitamin D binding protein because of one’s ethnicity.

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References

Owens, D.J., Allison, R., Close, G.L. Vitamin D and the Athlete: Current Perspectives and New Challenges. Sports Med. 2018; 48(Suppl 1): 3-16.

Larson-Meyer E. The Importance of Vitamin D. Sports Science Exchange. The Gatorade Sports Science Institute. 2015; 28 (48): 1-6

Ogan, D., Pritchett, K. Vitamin D and the Athlete: Risks, Recommendations, and Benefits. Nutrients. 2013; 5: 1856-1868

Willis, K.S., Smith, D.T, Broughton, K.S., et al. Vitamin D status and biomarkers of inflammation in runners. J Sports Med. 2012; 3: 35-42

Willis, K.S.; Peterson, N.J.; Larson-Meyer, D.E. Should we be concerned about the vitamin D status of athletes? Int. J. Sport Nutr. Exerc. Metab. 2008; 18, 204–224

Martineau, A.R., Jolliffe, D.A., Hooper, R.L., et al. 2017. Vitamin D supplementation to prevent acute respiratory tract infections: systematic review and meta-analysis of individual participant data. 356:i6583.