Vitamin D

Extra vitamin intake hasn’t always been shown to be important for athletes or bodybuilders except in the case of Vitamin D. This vitamin has been shown to slightly improve testosterone production and may improve recovery from exercise and increase muscle strength. 3000-5000 IU per day appears to be the optimal dose for receiving positive benefits.

Reference 1: Ceglia, L., & Harris, S. S. (2013). Vitamin D and its role in skeletal muscle. Calcified Tissue International, 92(2), 151-162.

Reference 2:  Pilz, S., et. al. (2011). Effect of vitamin D supplementation on testosterone levels in men. Hormone and Metabolic Research, 43(3), 223.