With the winter months now here and the exposure to sunlight becoming few and far between, the majority of people will become vitamin D deficient. Furthermore, with the majority of people training inside to avoid the cold weather, the athlete’s exposure to the fire burning ball in our skies becomes extremely limited. This will not only affect our health during the cold days and nights ahead but importantly for athletes, being deficient in vitamin D can also affect our performance (Close et al., 2013).
Vitamin D is sometimes referred to as a pro-hormone that possesses properties that are vital for many target tissues in the body including skeletal muscle. There are two forms of vitamin D known as D2 (ergocalciferol) and D3 (cholecalciferol). Small amounts of D2 come from fortified foods, plant foods and supplements whereas D3 comes from fortified foods and animal foods (fish, eggs and liver). The majority of vitamin D is internally manufactured in the liver and to a lesser extent in the kidney by the action of UV light. This occurs when your skin is exposed to the sun on a vitamin D precursor in the skin. Vitamin D is a fat-soluble vitamin along with vitamin A, E and K and therefore is stored in our fat cells for use when it is needed. Considering vitamin D is constantly being used for calcium metabolism and bone remodeling, it is crucial that athletes who train indoors during the winter months especially, do not become deficient. It appears the lowest intakes of calcium and vitamin D are reported in athletes where body image and body weight are important. For example Boxers and Jockeys typically dehydrate and consume inadequate amounts of vital micronutrients whilst trying to make weight for their corresponding sports (Wilson et al., 2013).
In addition to athletes, adequate intakes of vitamin D are crucial for older individuals given the importance in maintaining bone integrity and the potential decrease in endogenous production that is observed aging. The natural process of aging reduced the capacity of the skin to synthesize vitamin D precursors (MacLaughling & Holick, 1985) and decreases renal production of activated vitamin D3 (Tsai et al., 1984).If we are going to advise athletes to consume vitamin D from supplements then it is vital that it is the D3 form as this is roughly 9 times more active than the D2 from. Understanding how deficient each individual is can only be achieved through a blood test. Although this will cost money, there are many available tests to buy online that can be done at home and then sent away for analysis. Once you know the extent of the deficiency you can provide the athlete with the correct amount to consume. Some of the athletes I work with consume 2,000 – 4,000 International Units daily. Nutrition X’s Ultimate and BCAA Plus products both contain 1000 International Units per serving.
Taking into consideration that vitamin D is a fat soluble vitamin and will therefore accumulate in the fat cells over time; following a 4-6 week period we will begin to see a change in the deficiency level. Following 3 months it have been reported that you can correct the deficiency all together but understanding how deficient the individual was in the first place will obviously change this time period.
James Morehen Nutrition X Sports Scientist and Widnes Vikings Performance NutritionistTwitter – @Jmorehen ReferencesClose GL, Russell J, Cobley JN, Owens DJ, Wilson G, Gregson W, Fraser WD, Morton JP. 2013. 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. J Sports Sci, vol. 31(4), 344-353.MacLaughlin, J., & Holick, M. F. (1985).
Aging decreased the capacity of human skin to produce vitamin D3, J Clin Invest, 76: 1536.Tsai, K. S., Heath, H., Kumar, R., Riggs, B. L. (1984). Impaired vitamin D metabolism with aging women: possible role in pathogenesis of senile osteoporosis.
J Clin Invest, 73: 1668-1672.Wilson G, Fraser WD, Sharma A, Eubank M, Drust B, Morton JP, Close GL. 2013. Markers of bone health, renal function, liver function, anthropometry and perception of mood: a comparison between Flat and National Hunt Jockeys. Int J Sports Med, vol. 34(5), 453-459. December 9, 2014