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As mentioned before, micronutrients, including vitamin supplements, are widely used in the general population and by athletes, and have a variety of clinical applications. Similar to Part 39, we have again devoted an entire part of our A–Z series to vitamin supplementation—this time to vitamin D. Vitamin D was first discussed in our A–Z series in an earlier article on calcium and other bone health nutrients in 20101. In Part 40, the topic of vitamin D has been discussed anew by our current author in the context of more recent literature.
D E Larson-Meyer
It is well recognised that vitamin D plays an important role in calcium regulation and bone health. Emerging evidence, however, also suggests that vitamin D plays important roles in immune and inflammatory modulation and skeletal muscle function, and therefore has the potential to impact upon the health, training and performance of athletes. This paper provides an overview of the potential importance of vitamin D and vitamin D supplementation on the health and performance of athletes, and offers guidelines for appropriate supplementation.
Vitamin D synthesis and sources
Although vitamin D is thought of as a ‘'vitamin’, required amounts can be obtained entirely from cutaneous synthesis via exposure to ultraviolet-B (UVB) radiation in sunlight.2 Cutaneous synthesis of vitamin D, however, is dependent on factors including time of exposure, season, latitude, cloud cover, smog, skin pigmentation, sunscreen coverage and age. Vitamin D is not synthesised during the winter at latitudes greater than 35–37° north or south because insufficient UVB photons reach the earth's surface during these months.2 ,3
Vitamin D is also obtained in the diet from limited natural and fortified sources (table 1). Dietary vitamin D includes vitamin D3 (cholecalciferol, derived from animal sources) and vitamin D2 (ergocalciferol, derived from UVB exposure of fungi and yeast ergosterols).2 Both …
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