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by dietitian 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:

• Train indoors
• Train only in the early morning and late afternoons,
• Always cover up their skin,
• Regularly apply sunscreen,
• Live in a cool cloudy environment.

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.

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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:

• Sun Exposure: some sun exposure is essential to maintain acceptable Vitamin D levels. Current sun exposure guidelines are cautious to avoid skin cancer, and provide challenges due to the variability of individual skin types, distance from equator, and time of the year. Although there is minimal risk of vitamin D toxicity through sun exposure, it is not the safest way to improve vitamin D status.
• Dietary sources: There are only a few dietary sources of vitamin D from limited natural and fortified foods including fatty fish, egg yolks, sun-dried mushrooms, and fortified milk, margarine, and cereals. Dietary recommendations for vitamin D intake are generally not well achieved by athletes, therefore dietary advice from a sports dietitian to optimize intake is important.
• Supplementation: studies have shown that individual supplementation in athletes can achieve vitamin D sufficiency and is recommended in the winter months to maintain levels for those at risk.
• Food Fortification: vitamin D food fortification is in different stages around the world.

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

• Larson-Meyer DE, Willis KS. Vitamin D and athletes. Curr Sports Med Rep. 2010;9(4):220–226.
• Halliday TM, Peterson NJ, Thomas JJ, Kleppinger K, Hollis BW, Larson-Meyer DE. Vitamin D status relative to diet, lifestyle, injury, and illness in college athletes. Med Sci Sports Exerc. 2011 Feb;43(2):335-43. doi: 10.1249/MSS.0b013e3181eb9d4d.
• Owens DJ, Fraser WD, Close GL. Vitamin D and the athlete: Emerging insights. Eur J Sport Sci. 2014 Aug 18:1-12. [Epub ahead of print] doi: 10.1080/17461391.2014.944223
• Magee PJ, Pourshahidi LK, Wallace J MW, Cleary J, Conway J, Harney E, Madigan SM.Vitamin d status and supplementation in elite irish athletes. Int J Sport Nutr Exerc Metab. 2013 Oct;23(5):441-8.
• Willis KS, Smith DT, Broughton KS, Larson-Meyer DE. Vitamin D status and biomarkers of inflammation in runners. Open Access J Sports Med. 2012 Apr 27;3:35-42. doi: 10.2147/OAJSM.S31022.eCollection 2012.
• Allison RJ, Farooq A, Hamilton B, Close GL, Wilson MG. No Association between Vitamin D Deficiency and Markers of Bone Health in Athletes. Med Sci Sports Exerc. 2014 Jul 23. [Epub ahead of print] doi: 10.1249/mss.0000000000000457
• Valtueña J, Dominguez D, Til L, González-Gross M, Drobnic F. High prevalence of vitamin D insufficiency among elite spanish athletes the Importance of outdoor training adaptation. Nutr Hosp. 2014 Jul 1;30(n01):124-131.
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• Villacis D, Yi A, Jahn R, Kephart CJ, Charlton T, Gamradt SC, Romano R, Tibone JE, Hatch GF 3rd. Prevalence of Abnormal Vitamin D Levels Among Division I NCAA Athletes. Sports Health. 2014 Jul;6(4):340-7. doi: 10.1177/1941738114524517.
• Peeling P, Fulton SK, Binnie M, Goodman C. Training environment and Vitamin D status in athletes. Int J Sports Med. 2013 Mar;34(3):248-52. doi: 10.1055/s-0032-1321894.
• Shuler FD, Wingate MK, Moore GH, Giangarra C. Sports health benefits of vitamin D. Sports Health. 2012 Nov;4(6):496-501. doi: 10.1177/1941738112461621.
• He CS, Handzlik M, Fraser WD, Muhamad A, Preston H, Richardson A, Gleeson M. Influence of vitamin D status on respiratory infection incidence and immune function during 4 months of winter training in endurance sport athletes. Exerc Immunol Rev. 2013;19:86-101.
• Dubnov-Raz G, Rinat B, Hemilae H, Choleva L, Cohen A, Constantini N. Vitamin D Supplementation and Upper Respiratory Tract Infections in Adolescent Swimmers: A Randomized Controlled Trial. Pediatr Exerc Sci. 2014a Jul 15. [Epub ahead of print] doi: 10.1123/pes.2014-0030
• Cannell JJ, Hollis BW, Sorenson MB, Taft TN, Anderson JJ. Athletic performance and vitamin D. Med Sci Sports Exerc. 2009 May;41(5):1102-10. doi: 10.1249/MSS.0b013e3181930c2b.
• von Hurst PR(1), Beck KL. Vitamin D and skeletal muscle function in athletes. Curr Opin Clin Nutr Metab Care. 2014 Aug 16. [Epub ahead of print] doi.org/10.1097/mco.0000000000000105
• Wyon MA, Koutedakis Y, Wolman R, Nevill AM, Allen N. The influence of winter vitamin D supplementation on muscle function and injury occurrence in elite ballet dancers: a controlled study. J Sci Med Sport. 2014 Jan;17(1):8-12. doi: 10.1016/j.jsams.2013.03.007.
• Lewis RM, Redzic M, Thomas DT. The effects of season-long vitamin d supplementation on collegiate swimmers and divers. Int J Sport Nutr Exerc Metab. 2013 Oct;23(5):431-40.
• Shanely RA, Nieman DC, Knab AM, Gillitt ND, Meaney MP, Jin F, Sha W, Cialdella-Kam L. Influence of vitamin D mushroom powder supplementation on exercise-induced muscle damage in vitamin D insufficient high school athletes. J Sports Sci. 2014;32(7):670-9. doi: 10.1080/02640414.2013.847279.
• Close GL, Leckey J, Patterson M, Bradley W, Owens DJ, Fraser WD, Morton JP. The effects of vitamin D(3) supplementation on serum total 25[OH]D concentration and physical performance: a randomised dose-response study. Br J Sports Med. 2013b. Jul;47(11):692-6. doi: 10.1136/bjsports-2012-091735.
• Dubnov-Raz G, Livne N, Raz R, Cohen AH, Constantini NW. Vitamin D Supplementation and Physical Performance in Adolescent Swimmers. Int J Sport Nutr Exerc Metab. 2014b Sep 8. [Epub ahead of print] doi: 10.1123/ijsnem.2014-0180
• Nieman DC, Gillitt ND, Shanely RA, Dew D, Meaney MP, Luo B. Vitamin D2 supplementation amplifies eccentric exercise-induced muscle damage in NASCAR pit crew athletes. Nutrients. 2013 Dec 20;6(1):63-75. doi: 10.3390/nu6010063.
• Fitzgerald JS1, Peterson BJ, Warpeha JM, Wilson PB, Rhodes GS, Ingraham SJ. Vitamin D Status and VO_2peak during a Skate Treadmill Graded Exercise Test in Competitive Ice Hockey Players. J Strength Cond Res. 2014 May 14. [Epub ahead of print] doi: 10.1519/jsc.0000000000000523
• Dubnov-Raz G, Livne N, Raz R, Rogel D, Cohen AH, Constantini NW. Vitamin d concentrations and physical performance in competitive adolescent swimmers. Pediatr Exerc Sci. 2014c Feb;26(1):64-70. doi: 10.1123/pes.2013-0034.
• Larson-Meyer E. Vitamin D supplementation in athletes. Nestle Nutr Inst Workshop Ser. 2013;75:109-21. doi: 10.1159/000345827.

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Related Pages

• Vitamin D – the effect of deficiency on health
• Vitamin D Testing
• Vitamin Supplements
• Guide to Athletic Supplements