Sports Nutrition 101

With the winter months behind us, it’s time to get back out in the sun! Over the past few years, vitamin D deficiency has come into the spotlight for impacting sports performance. With over 77 percent of the general population considered vitamin D insufficient, it’s highly likely that many athletes also fall into this category. The most common symptom of vitamin D deficiency is muscle weakness, followed closely by general fatigue, headaches and stress fractures.

Vitamin D is important for bone growth and density. Without adequate amounts, low vitamin D levels will increase bone turnover increasing the risk for a bone injury, such as a stress fracture. So how do we prevent low levels of vitamin D? Most people immediately think of the sun. While the sun is our best source of vitamin D, there are many reasons why we don’t absorb enough:

• Usually, we aren’t the right distance from the equator. The time of day is critical for
  absorbing vitamin D.
• Depending on the season and cloud cover, there may not be the right rays of sunshine
  coming down.
• Sunblock — SPF15, which is important for protection, results in a 99-percent decrease in
  vitamin D absorption.
• Skin pigment — the darker the skin, the harder it is to absorb vitamin D.

Some foods naturally contain a significant amount of vitamin D. These include fatty fish such as salmon, egg yolks, and some fortified products like milk, cereal and orange juice. Even though these foods contain a good amount of vitamin D, the problem happens when it comes to digestion. The process of actually absorbing dietary vitamin D is only about 50-percent efficient, leaving much of the nutrient value lost in digestion. Because the challenge of consuming enough vitamin D to keep muscles healthy, most experts agree it will take a combination of sun, food and supplementation.

Here are the current recommendations for supplement use:

Ogan, D and Pritchett, K. Vitamin D and the Athlete: Risks, Recommendations, and Benefits. Nutrients 2013, 5(6), 1856-1868; doi:10.3390/nu5061856

If you’ve had your vitamin D level checked by the doctor and know your levels (ask next time you visit if you don’t!), here’s a quick guide:

Shuler, F et al. Sports Health Benefits of Vitamin D. Sports Health: A Multidisciplinary Approach OnlineFirst, October 2, 2012 as doi:10.1177/1941738112461621

< 20ng/mL – considered deficient
< 40ng/mL – considered enough for metabolic needs
> 40ng/mL – vitamin D stored in muscle and fat for future use
Toxicity seen > 150ng/mL

This graph from a 2012 paper on Vitamin D & Athletic Performance is a great summary:
• Athletes with levels between 40-50ng/mL show improved VO2 max, reduced inflammation and
  improved immune system function.
• Recommendations: Athletes with a deficiency need up to 5000IU/day for eight weeks. Once they
  are in a good range, 1000-2000IU/day is sufficient for maintenance. Get your levels checked!

Since there are so few foods high in vitamin D (unless you eat wild salmon almost daily), this is one of the rare times that supplementation may be the best choice. Make sure to use a brand that is third-party tested (Check USP or NSF to see brands). Also check that you are getting vitamin D3, the active form that the body absorbs the best. Most multivitamins have ~800-1000IU of vitamin D3. If you aren’t deficient, this is a good maintenance level to go along with vitamin D rich foods.