Effects of Vitamin D on Skeletal Muscle Strength in Resistance Trained Adult Females

The majority of vitamin D research has been done in non-athletic populations, particularly older populations, to analyze muscle weakness, pain, balance, and fractures. It has been reported that over a billion people worldwide are vitamin D deficient, including 36-70% of the young adult population. Previous literature also suggests that, even among healthy athletes, over 50% of subjects sampled had inadequate or insufficient vitamin D levels. Vitamin D deficiency can occur in young women, including pregnant women, and the risk of deficiency is even higher with advancing age in a woman's lifecycle. It is known that preserving skeletal muscle (SM) function is critical for women of all ages to prevent sarcopenia. Two factors in preserving SM are protein intake and resistance training. Relatively unknown are the actions of Vitamin D on SM function. Vitamin D deficiency can have a negative effect on SM function . However, additional research is needed to investigate the increase in SM strength when the serum concentration of vitamin D is improved. It is possible that an athlete may require an increased intake of vitamin D to assure adequate availability and storage for optimal performance; however, is known that food sources of vitamin D are limited in sufficient quantity to meet these requirements. Athletes who are insufficient will require a supplement of vitamin D3 for up to 5000 IU/day for at least eight weeks, to potentially reach optimal levels, then 1000-2000 IU/day for maintenance.