Those of us who live in northern climes make sure to enjoy the sunshine during our brief spring and summer. Given the evolutionary importance of vitamin D and the role sunlight plays in testosterone regulation, lack of sunlight can play a critical role in health. For most weekend warriors and student athletes, fewer than 5 hours/week are spent in direct sunlight. This raises the questions- is vitamin D supplementation necessary?
It has been well documented that low vitamin D leads to poor performance but is supplementing really needed? Wyon, et al; 2013 decided to find out. They took a ballet company. Divided the dancers; 17 performed all their training and took vitamin D (2000IU/day) while 7 dancers received placebo. This was done for 4 months.
Isometric strength and vertical leap were used as outcome measures as well as injury rate. The supplemented group displayed an increase of 18.7% (p<.01) in strength and 7.1% (p<.01) in vertical leap. They also displayed fewer injuries (p<.01). This would tend to indicate that if you are training at a high intensity at not getting a lot of sun exposure, grabbing a bottle of vitamin D might be worthwhile. Train safe.