There's a good chance you're deficient in vitamin D.
How do I know? Because I'm deficient in vitamin D. Well, I was when I got my blood tested a few weeks ago. I've made some changes since then, so I'm hoping that's no longer the case. I know what you're thinking—"just because some guy on the internet's deficient in vitamin D doesn't mean I am." Valid point. But what if I told you that half the New York Giants roster was deficient in vitamin D? Yep, it's true. In 2014, a team-wide blood analysis found that more than 50 percent of the players on the Giants roster had a vitamin D deficiency. To make things even more interesting, a growing amount of research is finding that vitamin D plays a crucial role in athletic performance.
Here's why every athlete needs to pay attention to vitamin D.
The Athletic Vitamin
Along with vitamins A, E and K, vitamin D is a fat-soluble vitamin, meaning it gets absorbed in fat globules and then travel through the body and into the blood stream.
Historically, vitamin D has been closely associated with bone health. That is indeed one of its most important roles, as the body needs vitamin D to absorb calcium. Vitamin D helps protect bones and calcium is crucial for building them. However, vitamin D's benefits extend well beyond bone health. It also plays a role in cell growth, blood pressure, immune function and reduction of inflammation. But its biggest benefit of interest to athletes is its potential impact on performance.
"Vitamin D is so important for performance. We used to think it only impacted bone health, but more and more studies have shown that it acts like a hormone and actually has a role in muscle function. It's very important for athletes," says Dr. Maren Fragala, Director of Athlete Health and Human Performance for Quest Diagnostics.
Vitamin D has been found to impact performance in a variety of ways. A recent study conducted by Precision Nutrition found that when athletes entered a workout with "optimal serum vitamin D concentrations," they went on to recover faster and more efficiently. "More pre-exercise vitamin D meant less post-exercise muscle weakness and better recovery through the entire recovery process. Less pre-exercise vitamin D meant more weakness and worse recovery," the study's authors wrote.
A different study, published in the Journal of Strength and Conditioning Research, found a "positive relationship between a measure of cardiovascular fitness and serum 25-hydroxyvitamin D, and a negative relationship between serum 25-hydroxyvitamin D and BMI." A third study, published in the journal PLOS One, found that vitamin D levels had a strong correlation with performance levels of professional soccer players. "Findings suggest that vitamin D levels are associated with the ergonometric evaluation of muscle strength … sprinting capacity and VO2 max in professional soccer players," the authors wrote.
Perhaps most intriguing was the 2015 study published in the American Journal of Sports Medicine, which found that "professional football players with higher vitamin D levels were more likely to obtain a contract position in the National Football League." Essentially, players with optimal vitamin D levels performed significantly well enough to win.
More research needs to be done on the link between athletic performance and vitamin D, but the studies currently available certainly indicate a positive relationship.
Essential Yet Elusive
We've established that many athletes are unknowingly deficient in vitamin D and that vitamin D is especially important for athletes. How do athletes go about raising their vitamin D levels?
Dietary sources of vitamin D are scarce, but it is found in egg yolks, fatty fish and fortified products like cereals and milk. However, the easiest way to get vitamin D is from sunlight. Human skin creates significant amounts of vitamin D when it's exposed to sunlight.
How long should you soak up the sun if you want to receive adequate amounts of vitamin D? According to the Vitamin D Council, "you only need to expose your skin for around half the time it takes for your skin to turn pink and begin to burn."
Athletes who live in northern latitudes tend to have lower vitamin D levels, especially during the winter months. When the weather is cold and the days are short, there are few opportunities for outdoor training. Indoor sport athletes are more frequently deficient than outdoor sport athletes, and those with darker skin pigment are naturally at a higher risk.
However, living in a warm, sunny climate doesn't automatically guarantee adequate levels of vitamin D. In fact, it was recently discovered that more than one-third of the student-athlete population at the University of Southern California had low levels of vitamin D. In reality, any athlete from any place can be low in vitamin D.
So, how much vitamin D do you actually need? The Institute of Medicine recommends 600 daily International Units for most adults, but many sports dietitians recommend higher amounts for athletes. A recent article from The Wall Street Journal states that "some sports dietitians encourage athletes to get 1,000 to 2,000 IU [of vitamin D] daily."
Addressing Your Own Levels of Vitamin D
The tricky thing about vitamin D is that it's shockingly easy for people with healthy lifestyles to come up short. The fact that many elite athletes are low in vitamin D is plenty proof of that. Since adequate amounts of vitamin D can be hard to come by, many take it in the form of a supplement. If you go that route, select a vitamin D3 supplement, since that form most closely approximates the vitamin D naturally produced by the body.
It's also important to note that a magnesium deficiency, which is quite common among Americans, may be inhibiting your bodies ability to activate vitamin D. Therefore, a magnesium supplement could be a good investment.
Unlike your weight, vitamin D levels cannot be measured instantly. However, there are a couple of key signs that you might have low levels. Symptoms include noticeable physical weakness, depression and excessive sweating (especially from the face/head). If you want an exact reading of your vitamin D level, you need to submit to a blood test. You have a few options for this. The best is simply to ask your doctor. Many health insurance policies cover this kind of blood testing. Another option is to use the Vitamin D Council's in-home testing kit, which run $50.