One of the most important supplements for runners is Vitamin D. Vitamin D plays a number of roles in the body, and in the winter months maintaining Vitamin D levels can be a challenge. Most people know that we get Vitamin D from the sun, but that is only part of the story. We do get Vitamin D from the sun, but it’s only available in one wavelength of sunlight, UVB rays. UVB rays require a sun angle of 50 degrees above the horizon or more in order to penetrate Earth’s atmosphere.
This means Vitamin D is only available via sunlight during certain times of the year. For most of the United States that window is mid-spring to fall. A good rule of thumb to test the angle of the sun is by the length of your shadow. If the sun angle is 50 degrees you shadow will be slightly shorter than you are tall. The shorter it is, the higher the angle of the sun, and the higher your rate of Vitamin D production.
Supplements for Runners: Vitamin D’s Role
The reason vitamin D ranks so high on our supplements for runners list is because of the critical roles in plays in the body. The area we’ve seen the most impact is on calcium absorption and iron absorption. Prior to focusing on vitamin D supplementation a disproportionate number of bone related injuries occurred in the winter or early spring. Since paying close attention to vitamin D intake, the number of stress fractures we’ve had at ZAP has decreased markedly.
Vitamin D is also crucial to iron absorption, a vital marker for endurance performance. If you are suffering from low iron or anemia you should also take a look at your vitamin D levels. Years ago we had a ZAP athlete who had very low iron and despite supplementing couldn’t elevate his levels. We then found out his vitamin D levels were low and once he began taking vitamin D his iron levels recovered. Additionally, there has been research showing Vitamin D helps reduce inflammation in the body following exercise.
Proper Vitamin D Levels
While having low Vitamin D levels clearly has negative performance implications, there is no research showing having high Vitamin D levels is beneficial. It is possible to have toxic levels of Vitamin D, although that is incredibly rare and characterized most often by loss of appetite and GI distress. We typically like to see Vitamin D levels right around 50ng/mL in the ZAP athletes. Levels below 30ng/mL can inhibit performance and is worthy of supplementation. To get your blood test done you can go to your primary care physician and request a blood panel that includes testing for Vitamin D.
You can also get Vitamin D through a variety of foods, which is always the preference above supplements. However, if you are deficient it is worth supplementing initially to get your levels up. Most of the athletes on our team regularly supplement Vitamin D, especially in the winter because of the role it plays in so many body processes.
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