Authors: Larson-Meyer, D. E., & Willis, K. S.

Current Sports Medicine Reports (2010): 9(4), 220-226.

Commentary by Heather Hynes

Vitamin D has many known functions within the body and it is recognized that a high percentage of the population is deficient or maintains suboptimal levels of vitamin D. Research with an athletic population is limited but this review article highlights the importance of vitamin D screening and discusses the impact that suboptimal vitamin D status may have on bone health and sports performance. It is important to mention that as you read this review article that the current Recommended Dietary Allowance (RDA) values for vitamin D and the Upper Limit (UL) values set by the Institute of Medicine were revised in 2010; the current values are 600 IU/ day for individuals between 9-70 yrs and the UL is currently set at 4,000 IU/ day.

Vitamin D can be obtained from a few dietary sources; fatty fish, egg yolks, fortified cereals and dairy products. The main source of vitamin D is through direct sun exposure during the summer months. Of concern for Canadian athletes is the lack of exposure for the long winter months and due to our geographical location (above 35 to 37° degrees latitude) vitamin D cannot be synthesized even on a sunny winter day. The best indicator of vitamin D status is to monitor serum 25(OH)D concentrations. Sport physicians and sports dietitians should be requesting frequent assessments during the training year; especially for athletes who train indoors (combative sports, gymnastics, etc.), have a history of bone injuries, who limit dietary sources or who train in the early or later part of the day. This research article highlights key factors when conducting a clinical assessment of vitamin D status. Understanding the symptoms of vitamin D deficiency is very important for high performance coaches. Musculoskeletal pain and weakness are mentioned as symptoms that are often overlooked or ignored. Supplementation protocols at or above the current RDA values may be needed during the winter months to ensure optimal vitamin D status.