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Nutrition Tip: Vitamin D

Authors Merrie Wimmer and Steven Regalado are both medical professionals and experienced triathletes.

By Steven Regalado, R.N. and Merrie Wimmer, MLS (ASCP)

March 30, 2010

Our favorite journals, Triathlete magazine and Triathlon 220 (UK), have been buzzing about the importance of Vitamin D.

We get most of our Vitamin D from the sun; our skin converts the suns rays into Vitamin D (which is more of a hormone than a vitamin). Vitamin D is responsible for keeping our bones and connective tissues strong and promotes neuromuscular function.

But most of us have not had much sun exposure this year as the weather has been unusual- more rain and snow than normal. Also, when we go outside, most of us use sun block.  As a result, Vitamin D supplements are a must for any athlete. Check out

There are several Vitamin D products available but the most important for us is Vitamin D3 (cholecalciferol). D3 is converted to calcitrol by the liver and kidneys- and its impact is on regulation of calcium and phosphorus. We may not be getting enough D3 from our fortified food products so a supplement containing 700 to 1,000 IU is recommended (my web search for the exact amount yielded numbers form 700 to 1,000 and most manufacturers sell it as 1,000 – 1,500- 2,000 IU).

A simple blood test can determine the concentrations of vitamin D (D2 and D3).

The take away message here is that nutrition for athletes is more than just protein, carbohydrates, and electrolytes!