Dr. Cunningham: Whether from the sun, food or supplements, Vitamin D is important for athletic performance, recovery (column)
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Vitamin D is produced in the skin when our skin is exposed to sunlight. It can also be ingested by eating certain foods or taking it in supplement form.
Vitamin D deficiency is common in parts of the world far from the equator; in people who use sunscreen; those with darker skin; in people who dress in clothing that covers the majority of their body; those who are confined indoors; and those who avoid sun exposure.
One can see that people who live in the Vail Valley are especially at risk for Vitamin D deficiency — especially during our long winters. A recent review of the Vitamin D levels in over 2,000 athletes with a mean age of 22 found that more than 50 percent had Vitamin D inadequacy. Athletes who participate in mainly indoor sports (such as gymnastics, basketball and volleyball) are at higher risk of being deficient.
ROLE IN ATHLETICS
Vitamin D has an important role in calcium and phosphate regulation in our bodies, but more recently there is evidence that it has a significant role in how our skeletal muscle functions and repairs itself after injury.
The active form of Vitamin D, calcitriol, is chemically very similar to an anabolic steroid. One study showed that Vitamin D supplementation demonstrated a positive effect on upper and lower limb strength indices. In another randomized controlled trial, a group of athletes receiving Vitamin D supplementation had significantly increased vertical jump heights compared to those taking a placebo.
Similarly, in another study, athletes given Vitamin D supplementation had improved jumping and movement efficiency. Thus, maintaining a normal Vitamin D level is key for maximizing athletic performance.
REPORTS FROM PRO INJURIES
Vitamin D deficiency can also lead to injury, namely stress fractures. A study of Royal Marine recruits in the U.K. found that those recruits with Vitamin D deficiency had a 60 percent higher incidence of stress fracture than recruits with normal Vitamin D levels.
Other studies of military recruits echo these findings. Another study of NFL players found that players who had a history of fracture were found to have lower levels of Vitamin D compared to players with no history of fracture.
GETTING YOUR VITAMIN D
Athletes who train and compete in outdoor environments in the southern U.S. were not found to have Vitamin D deficiency for the most part as their skin gets good sun exposure.
However, given the Vail Valley’s colder climate and the fact that many of us do not get sufficient sun exposure much of the year while we are bundled up in clothing or working out indoors, I would recommend supplementing with Vitamin D. Daily Vitamin D supplementation has been found to be more effective than weekly or monthly supplementation.
As for adverse effects with supplementation, there has been some concern that taking high levels of Vitamin D could cause kidney stones, but this correlation has not been demonstrated. However, taking excessive calcium supplements can lead to kidney stones and other problems. For this reason, I recommend taking just a Vitamin D supplement each day without additional calcium and just getting adequate calcium in your diet by eating leafy greens and other plant sources of calcium.
Vitamin D is not currently a banned substance per WADA. For general overall health and for those athletes looking to maximize athletic performance, I would recommend taking a Vitamin D supplement on a daily basis (1,500 IU of D3 per day) or getting at least 10 minutes of sun exposure to a significant portion of your skin each day.
Dr. Rick Cunningham is a knee and shoulder sports medicine specialist with Vail-Summit Orthopaedics. He is also a physician for the U.S. Ski Team. Visit his website at http://www.vailknee.com. For more information about Vail-Summit Orthopaedics, visit http://www.vsortho.com.