Shedding light on the sunshine vitamin
VITAMIN D IS ESSENTIAL for maintaining bone health. But mounting evidence is revealing many more ways this nutrient is crucial to a runner's overall health—safeguarding muscle strength, shoring up immunity,and easing inflammation. Here's what you need to know about vitamin D and how to make sure you're getting enough.
THE BASICS-AND HOW MUCH?
-> Vitamin D is created in your body from exposure to sunlight. It travels through your bloodstream, becoming a potent hormone that wakes up receptors in your intestines to start absorbing calcium.
Recent studies show that other organs, muscles, and body tissues are equipped with receptors, too. To sustain optimal amounts of the nutrient in our bodies, the current recommended daily allowance (which was based on bone health alone and assumes little or minimal sun exposure) is 600 international units (IU) a day for everyone through age 70 (800 IU if you're older). Many scientists,physicians, and nutritionists (myself included) don't believe that's enough to reap the full benefits, and advocate daily doses of 1,000 to 3,000 IU.
D ON RUNNING DUTY
-> On top of reducing the likelihood of stress fractures, healthy vitamin D levels have been shown to reduce the likelihood of overuse injuries and help quiet soreness in muscles after a race or hard workout. In 2011, researchers at the University of Wyoming discovered that a key inflammatory marker rises exponentially in runners when the amount of vitamin D in the bloodstream drops below a certain point. In that same study, student athletes with low levels of vitamin D were more likely to be sidelined due to a cold or the flu, compared to teammates with normal vitamin D in the bloodstream.
SUN VS. SUPPLEMENTS
-> Experts agree it's difficult for most people to get enough vitamin D through their diets (see"Where's the D?"). The sun's UV rays are our best bet, but even during the summer months the sun is strong enough for vitamin D production only between the hours of 10 a.m. and 3 p.m. and it needs to hit more than our hands and faces.
That's obviously not great for most runners. And sunscreen, which we need to prevent skin cancer, cuts production by 99 percent. That leaves supplements. Discuss your individual needs with your doctor or nutritionist, who may recommend a simple blood test before determining an appropriate supplement amount. Once you've had that conversation, look for brands that contain vitamin D3 (cholecalciferol) rather than vitamin D2 (ergocalciferol) and without herbs, which can interfere with D's function.
source: Runner_World_US_Feb2012
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