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| Feb 07, 2014
Written By Alan Remde, M.D., FAAFP
Vitamin D (actually a hormone), is an essential fat-soluble hormone required for the health of the bones, muscles, heart and blood vessels, nervous, immune and other systems of the body. Given that many of these systems are critical for athletic performance, the adequacy of vitamin D status is relevant for Olympic athletes.
Sources & requirements: The majority (~ 90%) of vitamin D is derived from direct sunlight (cannot be through windows, sunscreens or clothes) when the sun is at least 40 degrees above the horizon. Thus at latitudes above 35 degrees, there is a “vitamin D winter” when none of us can make enough vitamin D from the sun, and we rely on stored vitamin D banked during the warmer months. The amount of sunlight needed is modest – in the range of 10 to 45 minutes per day, and thus should not pose a significant risk of skin cancer in most people. This range varies due to factors such as darkness of the skin, older age, air pollution and many other factors that reduce the ability to make Vitamin D from sunlight. For example, for people with medium-light skin who gradually tan but sometimes burn (Skin Type 3), 15-30 minutes of sunlight most days is probably adequate. Only a small proportion comes from dietary sources such as oily fish and fortified dairy products, and these should not solely be relied on to satisfy the body’s total requirement.
Vitamin D deficiency is common in athletes. Deficiency is associated with osteoporosis (thinning of bones), stress fractures, muscle weakness, falls, poor coordination, depression and fatigue, as well as many other problems. More research is required to confirm that optimizing Vitamin D levels improves performance. (Cannell, J. J., et. al. Athletic Performance and Vitamin D. Med. Sci. Sports Exerc., Vol. 41, No. 5, pp. 1102–1110, 2009).
Vitamin D status can be assessed with a blood test for 25 (OH) Vitamin D level. Normal is considered by many to be ~ 30 – 60 ng/ml. The range of normal 25 (OH) Vitamin D level is controversial, however. The IOM in a major recent review states that the lower limit of normal level is 20 ng/mL. There is also preliminary evidence suggesting that Afro-Americans can have even lower level than this and be healthy. This finding awaits confirmation.
Prevention: Taking 1000 to 2000 units daily of Vitamin D3 in the colder months will help maintain stores.
Deficiency is treated with higher doses, e.g. 50,000 units oral vitamin D3 weekly for 8–16 weeks. (Modern nutrition in health and disease/senior editor, Maurice E. Shils; associate editors, Moshe Shike…[et al.].—10th ed. Chapter on Vitamin D)
Discussion question: What other vitamins may be necessary for athletic success in the Olympic Games?