Vitamin D has been in the headlines quite a bit lately. Mainly the news has focused on how much one should take each day. Currently the recommended daily allowance is 200IU(Internal Units). Most experts agree that this is too low. Vitamin D is a water soluble vitamin and would be very hard to take enough to reach toxic levels, but still there's a wide range of opinions on how much to take. From what I've read, most at least agree that 200IU is too low and many recommend upping it to at least 400IU, but many others recommend much higher amounts. I recommend that you consult with your doctor about the right amount for your own personal needs. Because of my IBD, I take 2000IU daily, but that may not be appropriate for everyone.
The current issue of Runner's World (Dec. 2009) features an article on the benefits of Vitamin D for runners. According to the article it may boost your running performance (if you're taking enough). The article sites research from the March 2009 Archives of Internal Medicine that reports over 3/4 of adults are Vitamin D deficient. A separate study from the Cooper Clinic in Dallas showed that runners are no different than the general population. This 2008 study showed that 75% of the research participants averaging 20 miles a week had low Vitamin D levels.
In addition to the possible cancer, diabetes, and heart disease risk-lowering benefits of Vitamin D, researchers now believe it may also help boost athletic performance. A 2008 study showed that adolescents with high levels of Vitamin D could jump higher, quicker, and with more power. A different 2008 study showed that Vitamin D increases the size of fast-twitch muscles and muscular strength. Other research shows that low levels of Vitamin D may make an athlete more prone to injury such as stress fractures.
According to the Runner's World article, Michael F. Holick, M.D., Ph.D., Professor of medicine, physiology, and biophysics at Boston University of School of Medicine and author of the upcoming book, The Vitamin D Solution, recommends that runners take a supplement that contains 2000IU of Vitamin D. Hey! That's what I take! Cool!
Be careful. All Vitamin D is not created equal. When looking at a supplement, be sure it contains Vitamin D3 (choledalciferol). From what I understand, supplements use either Vitamin D2 (ergocalciferol) or Vitamin D3 (choledalciferol). Most experts recommend using a supplement made of Vitamin D3 (which is typically naturally sourced and better used by the body). Vitamin D2 in high doses can actually be toxic to the body.
Good sources (natural, fortified, or enriched) of Vitamin D include:
• mushrooms (enriched)
• fish (salmon, mackerel, sardines [canned in oil], tuna [canned in oil])
• milk (fortified)
• margarine (fortified)
• cereal (fortified)
• whole egg
• swiss cheese
• cod liver oil (yum!?)
• yogurt (fortified)
• orange juice (if fortified)