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Get the Vitamin D Advantage: It May Boost Performance and Will Prevent Disease

Get the most out of your training by taking vitamin D. There’s a wealth of evidence that optimal vitamin D levels are linked with better athletic performance, and now that we’re going into shorter days with less sunlight, you’ll need to take a vitamin D supplement to perform at your best. Even if the only payback for taking vitamin D is less risk of injury, it’s well worth the money to keep you healthy through the winter.

The evidence that vitamin D deficiency is linked to stress fractures, chronic muscle pain, muscle injuries, and viral infections in athletes is clear. One review of the value of vitamin D for improving athletic performance notes, “those caring for athletes have the responsibility to promptly, diagnose, and adequately treat vitamin D deficiency.” And, because vitamin D in its active form is a steroid hormone, in 1940 the Germans noted that having athletes use a sun lamp to raise vitamin D levels may even constitute an “unfair advantage”! This view is excessive since athletes are commonly deficient in vitamin D and rarely deficient in other hormones that provide an unfair advantage such as testosterone or growth hormone. Why not take advantage of the vitamin D advantage during winter—the season in which athletic performance is typically at a low?

There is significant evidence that peak physical performance occurs in the late summer season, even when physical conditioning is consistent. There’s speculation that improved summer performance is linked  to naturally higher vitamin D levels from sun exposure, especially since seasonal evidence on athletic performance shows that it begins to decline in early fall. It then continues to decrease until the return of the sun, generally in the spring.

It’s possible vitamin D levels are not the cause, or are a factor of reverse causation—improved physical performance in the summer and higher vitamin D levels may be secondary to additional outdoor athletic training in warmer weather. However, if this were true, athletic performance should not decline until late autumn because early fall weather is generally ideal for outdoor training. Rather, the evidence shows an abrupt, unexplained decline in athletic performance beginning in early autumn when vitamin D levels start to decline. Interestingly, testosterone levels, which had at one point been  hypothesized as a reason for the typical decrease in athletic performance in the fall, tend to peak in the December, not summer.

More convincing is evidence that vitamin D helps preserve type II muscle fibers, particularly during periods of inactivity. Quadriceps muscle biopsies on 12 vitamin D-deficient individuals found atrophy of type II muscle fibers before treatment, with significant muscle growth and size after vitamin D supplementation. And, two years of treatment with 1,000 IUs of vitamin D a day significantly increased muscle strength, doubled the cross sectional area, and tripled the percentage of type II muscle fibers in the functional limbs of 48 severely vitamin D-deficient women who were paralyzed on one side of their bodies from a stroke.

Identifying a definitive role of vitamin D on performance is hard to do, but researchers point to the elite performance of equatorial athletes such as Kenyan runners who benefit from higher natural vitamin D from the sun-rich environment. This is impossible to prove as is the interesting case of the 1968 Summer Olympics in Mexico City. Researchers note that athletes had to arrive early and train in the sun-rich environment in order to acclimatize to the 7,400-foot altitude for weeks in advance. A surprising number of world records were set almost entirely in outdoor sports, and the percentage improvement in world records far exceeded the norm at these Games, supporting the connection of vitamin D and peak performance.

Take away from all this research that you should be supplementing with vitamin D daily (probably in a dose of 2,000 to 5,000 IUs) if you want to stay injury free and perform at your best. Be aware that during summer months when you are getting natural sun exposure, vitamin D production is hindered if you wear sun block or sunglasses. A surprisingly high level of vitamin D deficiency exists in Miami, despite the sun-drenched environment, likely because people are lathered in sun screen and wearing their shades.