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The Sun and Vitamin D: Improving Athletic Performance

Can spending more time in the sun improve athletic performance?

The ancient Greeks believed athletes should be well bathed by the sun, and their elite athletes trained at the beach, and in the nude. The latter might be difficult in today’s society, but if your vitamin D levels are too low, the sun can definitely improve your training and racing performance. Research indicates that serum vitamin D levels of about 50 ng/ml are associated with peak athletic performance. However, a surprisingly high number of athletes have levels of vitamin D far below that mark.

Despite spending significant time outdoors for training and competition, endurance athletes are not immune to the worldwide epidemic of low vitamin D levels. Many of these athletes inadvertently prevent normal vitamin D status by using sunscreen, avoiding midday sun exposure, and overdressing.

For decades, I’ve been finding low vitamin D levels in athletes and recommending more time in the sun. While this has resulted in my receiving some nasty letters from dermatologists and others, the research today is demonstrating that the problem is real. For example, Maimoun and colleagues recently published a study in the International Journal of Sports showing that a group of French cyclists, each training 16 hours a week outdoors, had below normal levels of vitamin D. Two other current studies measuring large numbers of people in southern Florida and southern Arizona show significantly high numbers of people were also far below normal levels of vitamin D, despite living in very sunny environments.

While it’s often not difficult to obtain sufficient amounts of vitamin D from the sun, there are a variety of reasons why endurance athletes, who spend most of their training times outside, may be unable to accomplish this:

  • The use of sunscreen blocks the vitamin D-producing ultraviolet B (UVB) waves of the sun.
  • Wearing of protective clothing, especially materials that block UVB waves.
  • Training early and later in the day, when vitamin D-producing sun exposure is significantly reduced.
  • Darker skin – in addition to those with naturally dark skin, most light-skinned athletes have accumulated enough sun to darken their skin, reduce their ability to obtain vitamin D from sun exposure; they need to be in the sun longer.
  • Proper fat metabolism is necessary for vitamin D production, and those with too high and too low body fat may be unable to release stored vitamin D, which is especially important in winter and early spring when sun exposure produces much less vitamin D.
  • Athletes living at more extreme latitudes, such as northern Europe and Canada, and southern Australia and South America, have significantly less sun exposure throughout the year.

It’s important to balance overexposure of the sun (avoiding sun burn) with adequate sun exposure that provides sufficient vitamin D production. Normalizing vitamin D levels has various benefits, including:

  • Improved muscle function
  • Prevent bone problems and other mechanical injuries
  • Help recovery from training and competition
  • Reduce unexplained muscle pains.
  • Prevent many health problems including many forms of cancer.
  • Normal vitamin D levels may also prevent getting sunburned during long training and racing.

While vitamin D is called a “vitamin,” it’s really a unique steroid hormone, which performs a number of different tasks in the athletic body and brain:

  • Helping muscles function better
  • Controlling inflammation and immunity
  • improving brain and hormone function
  • Regulating calcium absorption and utilization

Promoting the work of a couple thousand genes.For these reasons, low levels of vitamin D may adversely affect athletic performance. Conversely, the addition of vitamin D – both from additional sun exposure and supplementation – can increase performance. John Cannell, MD, executive director of the Vitamin D Council (, has extensively researched the question of vitamin D and athletic performance:


“If you are vitamin D deficient, the medical literature indicates that the right amount of vitamin D will make you faster, stronger, improve your balance and timing, etc. How much it will improve your athletic ability depends on how deficient you are to begin with. However, peak athletic performance also depends upon the neuromuscular cells in your body and brain having unfettered access to the steroid hormone, activated vitamin D.”


As the lead author of a study entitled “Athletic Performance and Vitamin D” (Med. Sci. Sports Exerc. 2009), Cannel reviewed reports on the use of sunlamps during the early and mid 1900s in Russia and East Germany to increase vitamin D levels in athletes. They showed this form of artificial ultraviolet irradiation, which increases vitamin D levels, improved athletic function. And, these actions caused some to argue that this little known routine provided an unfair advantage during competition. In my earliest days of training and competition in high school and college, there were often news reports about the well-kept secrets that helped former Soviet Union and East German athletes perform better; some claim this was one of their secrets.


“My Perspective,” by John Cannel, M.D.


“No way, doc.” I had just finished telling my patient about the benefits of vitamin D, telling him he should take 4,000 IU per day, using all the techniques I had learned in 30 years of medical practice to convince someone proper treatment is important. But, he knew the U.S. government said he only needed 200 IU per day, not 4,000. He also knew the official Upper Limit was 2,000 IU a day. “What are you trying to do doc, kill me?” I told him his 25(OH)-vitamin D blood test was low, only 13 ng/ml. He had read about that too, in a medical textbook, where it said normal levels are between 10 and 40 ng/ml. “I’m fine doc;” adding “Are you in the vitamin business?” I explained I was not; that the government used outdated values; that recent studies indicate ideal 25(OH)D levels are about 50 ng/ml; and that they indicated that he needed about 4,000 IU per day to get his level up to 50. “No thanks doc, I’m fine.”

So I tried a different tact. I brought him copies of recent press articles. “Look,” I said, “look at these.” Science News called vitamin D the Antibiotic Vitamin. The Independent in England says vitamin D explains why people die from influenza in the winter, and not the summer. U.S. News and World Report says almost everyone needs more. Newsweek says it prevents cancer and helps fight infection. In four different recent reports, United Press International says that: it reduces falls in the elderly, many pregnant women are deficient, it reduces stress fractures, and that it helps heals wounds.


He glanced at the articles, showing a little interest in stress fractures. Then he told me what he was really thinking. “Look doc, all this stuff may be important to old guys like you. I’m 22. All I care about are girls and sports. When I get older, maybe I’ll think about it. I’m too young to worry about it. I’m in great condition.” I couldn’t argue. He was in good health and a very good basketball player, playing several hours every day, always on indoor courts.


What could I do to open his eyes? As an African American, his risk of early death was very high, although the risk for blacks doesn’t start to dramatically increase until their 40’s and 50’s. Like all young people, he saw himself as forever young. The U.S. government was no help, relying on a ten-year-old report from the Institute of Medicine that is full of misinformation.


I tired to tell him that the 200 IU per day the U.S. government recommends for 20-year-olds is to prevent bone disease, not to treat low vitamin D levels like his. I pointed out the U.S. government’s official current Upper Limit of 2,000 IU/day is the same for a 300 pound adult as it is for a 25 pound toddler. That is, the government says it’s safe for a one-year-old, 25-pound, child to take 2,000 IU per day but it’s not safe for a 30-year old, 300-pound, adult to take 2,000 and one IU a day. I mean, whoever thought up these Upper Limits must have left their thinking caps at home. Nevertheless, nothing worked. My vitamin D deficient patient was not interested in taking any vitamin D.


What are young men interested in? I remembered that he had told me: “Sex and sports.” Two years ago I had researched the medical literature looking for any evidence vitamin D enhanced sexual performance. Absolutely nothing. That would have been nice. Can you imagine the interest?
Then I remembered that several readers had written to ask me if vitamin D could possibly improve their athletic performance? They told me that after taking 2,000 to 5,000 IU per day for several months, they seemed just a little faster, a little stronger, maybe had a little better balance and timing. A pianist had written to tell me she even played a better piano, her fingers moved over the keys more effortlessly! Was vitamin D responsible for these subtle changes or was it a placebo effect? That is, did readers just think their athletic performance improved because they knew vitamin D was a steroid hormone precursor (hormone, from the Greek, meaning “to set in motion”)?


The active form of vitamin D is a steroid (actually a seco-steroid) in the same way that testosterone is a steroid and vitamin D is a hormone in the same way that growth hormone is a hormone. Steroid hormones are substances made from cholesterol, which circulate in the body, and work at distant sites by “setting in motion” genetic protein transcription. That is, both vitamin D and testosterone regulate your genome, the stuff of life. While testosterone is a sex steroid hormone, vitamin D is a pleomorphic (multiple function) steroid hormone.

All of a sudden, it didn’t seem so silly. Certainly steroids can improve athletic performance although they can be quite dangerous. In addition, few people are deficient in growth hormone or testosterone, so when athletes take sex steroids or growth hormone they are cheating, or doping. The case with vitamin D is quite different because natural vitamin D levels are about 50 ng/ml and, since almost no one has such levels, extra vitamin D is not doping, it’s just good treatment. I decided to exhaustively research the medical literature on vitamin D and athletic performance. It took me over a year.


To my surprise, I discovered that there are five totally independent bodies of research that all converge on an inescapable conclusion: vitamin D will improve athletic performance in vitamin D deficient people (and that includes most people). Even more interesting is who published this literature, and when. Are you old enough to remember when the Germans and Russians won every Olympics in the 60’s and 70’s? Well, it turns out that the most convincing evidence that vitamin D improves athletic performance was published in old German and Russian medical literature.
With the help of my wife and mother-in-law, both of whom are Russian, and with the help of Marc Sorenson, whose book Solar Power is a must read, I finally was able to look at translations of much of the old Russian and German literature. When one combines that old literature with the modern English language literature on neuromuscular performance, the conclusion is inescapable. The readers who wrote me are right.


If you are vitamin D deficient, the medical literature indicates that the right amount of vitamin D will make you faster, stronger, improve your balance and timing, etc. How much it will improve your athletic ability depends on how deficient you are to begin with. How good an athlete you will be depends on your innate ability, training, and dedication. However, peak athletic performance also depends upon the neuromuscular cells in your body and brain having unfettered access to the steroid hormone, activated vitamin D. In addition, how much activated vitamin D is available to your brain, muscle, and nerves depends on having ideal levels of vitamin D in your blood – about 50 ng/ml, to be precise.


Why would I write about such a frivolous topic like peak athletic performance when cancer patients all across this land are dying vitamin D deficient? Like many vitamin D advocates, I have been disappointed that the medical profession and the public don’t seem to care about vitamin D. Maybe people, like my young basketball player, will care if it makes better athletes.


The medical literature indicates vitamin D levels of about 50 ng/ml are associated with peak athletic performance. Of course, recent studies show such levels are ideal for preventing cancer, diabetes, hypertension, influenza, multiple sclerosis, major depression, cognitive impairments, etc. But who cares about all that disease stuff old people get, we’re talking about something really important: speed, balance, reaction time, muscle mass, muscle strength, squats, reps, etc. And guess who’s now taking 4,000 IU/day? Yes he is, and he tells me his timing is better, he can jump a little higher, run a little faster, and the ball feels “sweeter,” whatever that means. (Thanks to Dr. John Cannell and the Vitamin D Council.)