Fundamentally, vitamin D is needed for calcium metabolism and calcium absorption in the body. It also regulates numerous genes and plays significant roles in regulating inflammation and immunity. In skeletal muscle, it has been shown that vitamin D is important for calcium regulation, protein synthesis and muscle growth. We can get an abundance of vitamin D from the conversion of 7-dehydrocholesterol in the skin during sun exposure and this topped off through dietary sources. According to current studies athletes are generally vitamin D deficient, which may impair muscle function and performance.
Still not convinced to take vitamin D? Well, a recent study presented at Experimental Biology 2015 in Boston MA suggests that one’s vitamin D status can predict their testosterone level. The team of scientists from East Carolina University and Womack Army Medical center (North Carolina) provided evidence suggesting that deficient blood vitamin D concentrations inhibit testosterone production and potentially limit human performance in extremely fit high-performance army personnel.
ACTION POINT: The best way to see if you are vitamin D deficient is to have your physician test your blood vitamin D (i.e., 25[OH]D) levels. Alternatively, there are a number of “finger prick” tests available online. Current research suggests that athletes should strive to achieve blood 25[OH]D levels greater than 75 nmol/L. As far as a dose is concerned, it has been shown that 2000–5000 IU of vitamin D3 per day for 8 weeks increases serum 25 [OH]D to optimal levels (greater than 75 nmol/L).
Laurel Wentz, Cristóbal Berry-Cabán, Jerad Eldred and Qiang Wu. Vitamin D Correlation with Testosterone Concentration in US Army Special Operations Personnel. April 2015 The FASEB Journal, vol. 29 no. 1 Supplement 733.5