Vitamin D Guidance for Athletes

People living in the UK are at risk of low vitamin D levels particularly in the Autumn and Winter months when the suns UV rays are not strong enough to create vitamin D (Holick, 2007). A high prevalence of vitamin D insufficiency has been reported among athletes in the UK. Some studies highlighted that approximately 65% of professional UK athletes had insufficient Vitamin D concentrations during winter months even when most of their training occurred outdoors (Close et al, 2013a; Morton et al, 2012). Screening amongst elite Welsh athletes has also identified a high prevalence of vitamin D insufficiency with more than 45% of athletes having insufficient or deficient vitamin D levels by October.

Although we call it a vitamin, vitamin D is a hormone which is mainly produced in our bodies from direct sunlight exposure on our skin. There are a few foods which contain small amounts of vitamin D including oily fish such as salmon or mackerel, red meat, eggs and some fortified breakfast cereals and fat spreads. Though even a healthy, balanced diet which provides us with all the other nutrients that we need is unlikely to provide enough vitamin D.

Vitamin D is essential for our bones and this is because we need vitamin D to help our bodies absorb calcium and phosphate, which are important for healthy bones, teeth and even muscles. Vitamin D deficiency can cause bones to become soft and weak making them more susceptible to injuries. Among athletic populations vitamin D insufficiency has been related to an increased risk of stress fractures (Larson-Meyer & Willis, 2010). Screening amongst Welsh athletes has identified that some individual athletes had low bone mineral density, of which low vitamin D may be a contributing factor and could make them more susceptible to injuries.

Vitamin D also plays an important role in many other aspects that may impact on an athlete’s overall health, performance and ability to train including their muscle function and immune health (Willis, Peterson & Larson-Meyer, 2008; Larson-Meyer & Willis, 2010).

Among young adults with vitamin D deficiency, significant improvements in 10-m sprint times and vertical jump height have been reported with supplementation of vitamin D (Close et al, 2013a). Faster recovery of muscle strength following intense exercise has also been reported with higher vitamin D concentrations (Barker et al, 2013). Among a cohort of 267 athletes, significantly more upper respiratory tract infection symptoms were presented among the vitamin D deficient group thank those with optimal vitamin D levels (He et al, 2013).

Some athletes may be at greater risk of low vitamin D levels, particularly those that spend very little time outdoors in the summer or for those whose training is predominantly based indoors. Similarly, athletes who cover up most of their skin when outside, for example with specific training kit or who routinely use sunscreen may also be more likely to have low vitamin D levels. Athletes with darker skin tones from Asian, African, Afro-Carribean and Middle Eastern descent living in the UK may also be more at risk of low vitamin D levels (Clemens et al, 1982; Matsuoka et al, 1987; Larson-Meyer, 2013).

To support athlete’s health, training and performance during the Autumn and Wintertime, the Sport Wales Institute Performance Nutrition and Clinical teams developed the Athlete Vitamin D Guidelines to disseminate to athletes across the system annually.

A research project amongst elite Welsh athletes showed that providing athletes with vitamin D guidelines alongside screening, provision of vitamin D supplementation and regular reminders throughout the Autumn and Winter months leads to good adherence and supports the maintenance of sufficient vitamin D levels throughout the Winter.

While some athletes are at greater risk of vitamin D deficiency than others, it is recommended that all athletes consider taking a vitamin D supplement to support their health and performance during the Autumn and Winter months (from the beginning of October until the end of March).

The project pulled together the research surrounding vitamin D supplementation and the development of the Athlete Vitamin D Guidelines.

In the UK all adults and children over the age of one are advised to consider taking a daily supplement containing 10 micrograms (400IU) of vitamin D especially during the Autumn and winter months. Athletes are generally recommended to consider taking a slightly higher amount of 25-50 micrograms of vitamin D (1,000-2,000IU) per day between October and April.

Too much vitamin D can also be harmful to the body and therefore athletes are advised to check all the supplements that they take to ensure they don’t take more than the upper limit. Children aged 1-10 shouldn’t take more than 50 micrograms (2,000IU) daily and adults shouldn’t exceed 100 micrograms (4,000IU) daily. It is important for athletes to check the content of all supplements that they use to ensure they don’t go above the upper limit.

Athletes must be very cautious when it comes to using supplements due to the genuine risk of contamination with prohibited substances. Consequently, all athletes are required to assess the need, risk and consequences before taking any supplementation in accordance with UKAD guidance on managing supplement risks. In addition, athletes are required to retain a record of all supplements taken. A recommended product which is batch tested as part of the Informed Sport Programme is the Healthspan Elite 1,000IU Vitamin D3

References:

Barker, T., Henrikson, V.T., Martins, T.B., Hill, H.R., Kjeldsberg, C.R., Schneider, E.D., Dixon, B.M., & Weaver, L.K. (2013). Higher Serum 25-Hydroxyvitamin D concentrations associate with faster recovery of skeletal muscle strength after muscular injury. Nutrients, 5, 1253-1275.

Clemens, T.L., Henderson, S.L., Adams, J.S., & Holick, M.F. (1982). Increased skin pigmentation reduces the capacity of skin to synthesise vitamin D. Lancet, 1, 74-76.

Close, G.L., Russell, J., Cobley, J.N., Owens, D.J., Wilson, G., Gregson, W., Fraser, W.D., & Morton, J.P. (2013a). Assessment of vitamin D concentration in non-supplemented professional athletes and healthy adults during the winter months in the UK: implications for skeletal muscle function. Journal of Sports Sciences, 31, 344-353.

Holick, M.F. (2007). Vitamin D deficiency. The New England Journal of Medicine, 357(3), 266-281. Larson-Meyer, E., & Willis, K.S. (2010). Vitamin D and athletes. Current Sports Medicine Reports, 9(4), 220-226.

He, C. S, Handzlik, M., Fraser, W. D., Muhamadi, A., Preston, H., Richardson, A., & Gleeson, M. (2013). Influence of vitamin D status on respiratory infection incidence and immune function during 4 months of winter training in endurance sport athletes. Exercise Immunology Review, 19, 86-101.

Matsuoka, L.Y., Wortsman, I.L., MacLaughlin, J.A., & Holick, M.F. (1987). Sunscreens supress cutaneous vitamin D3 synthesis. Journal of Clinical Endocrinology and Metabolism, 64, 1165-1168.

Morton, J.P., Iqbal, Z., Drust, B., Burgess, D., Close, G.L., & Brukner, P.D. (2012). Seasonal variation in professional soccer players of the English Premier League. Applied Physiology, Nutrition and Metabolism, 37, 1-5.

Willis, K.S., Peterson, N.J., & Larson-Meyer, E. (2008). Should we be concerned about the vitamin D status of athletes? International Journal of Sport Nutrition and Exercise Metabolism. 18, 204-224.