Vitamin D status relative to diet, lifestyle, injury, and illness in college athletes.

UNLABELLED: Vitamin D deficiency is endemic in the general population; however, there is much to be learned about the vitamin D status of athletes. PURPOSE: the purposes of this study were to assess the prevalence of vitamin D insufficiency in collegiate athletes and to determine whether 25(OH)D concentrations are related to vitamin D intake, sun exposure, body composition, and risk for illness or athletic injury. METHODS: 25(OH) vitamin D concentrations were measured in 41 athletes (18 men/23 women, 12 indoor/29 outdoor athletes) throughout the academic year. Dietary intake and lifestyle habits were assessed via questionnaire, bone density was measured by dual energy x-ray absorptiometry, and injury and illness were documented as part of routine care. RESULTS: the 25(OH)D concentrations changed across time (P = 0.001) and averaged 49.0 ± 16.6, 30.5 ± 9.4, and 41.9 ± 14.6 ng·mL (mean ± SD) in the fall, winter, and spring, respectively, and were higher in outdoor versus indoor athletes in the fall (P < 0.05). Using 40 ng·mL as the cutoff for optimal status, 75.6%, 15.2%, and 36.0% of athletes had optimal status in the fall, winter, and spring, respectively. 25(OH)D concentrations were significantly (P < 0.05) correlated with multivitamin intake in the winter (r = 0.39) and tanning bed use in the spring (r = 0.48); however, status was otherwise not related to intake, lifestyle factors, or body composition. 25(OH)D concentrations in the spring (r = -0.40, P = 0.048) was correlated with frequency of illness. CONCLUSIONS: our results suggest that collegiate athletes can maintain sufficient status during the fall and spring but would benefit from supplementation during the winter to prevent seasonal decreases in 25(OH)D concentrations. Results further suggest that insufficient vitamin D status may increase risk for frequent illness. Future research is needed to identify whether vitamin D status influences injury risk during athletic training or competition.

Should we be concerned about the vitamin D status of athletes?

A surprisingly high prevalence of vitamin D insufficiency and deficiency has recently been reported worldwide. Although very little is known about vitamin D status among athletes, a few studies suggest that poor vitamin D status is also a problem in athletic populations. It is well recognized that vitamin D is necessary for optimal bone health, but emerging evidence is finding that vitamin D deficiency increases the risk of autoimmune diseases and nonskeletal chronic diseases and can also have a profound effect on human immunity, inflammation, and muscle function (in the elderly). Thus, it is likely that compromised vitamin D status can affect an athlete's overall health and ability to train (i.e., by affecting bone health, innate immunity, and exercise-related immunity and inflammation). Although further research in this area is needed, it is important that sports nutritionists assess vitamin D (as well as calcium) intake and make appropriate recommendations that will help athletes achieve adequate vitamin D status: serum 25(OH)D of at least 75 or 80 nmol/L. These recommendations can include regular safe sun exposure (twice a week between the hours of 10 a.m. and 3 p.m. on the arms and legs for 5-30 min, depending on season, latitude, and skin pigmentation) or dietary supplementation with 1,000-2,000 IU vitamin D3 per day. Although this is significantly higher than what is currently considered the adequate intake, recent research demonstrates these levels to be safe and possibly necessary to maintain adequate 25(OH)D concentrations.