Vitamin D and skeletal muscle function in athletes.
To highlight recently published data about the vitamin D status of athletes, and effect of vitamin D supplementation on muscle strength and performance in the athletic population.The vitamin D receptor exists in skeletal muscle, and muscle weakness has been reported in individuals who are severely deficient [25(OH)D <25 nmol/l]. Experimental findings reveal the cellular and genomic mechanisms implicating vitamin D in muscle mass, strength and function, and raise questions about the role of vitamin D in the achievement of optimum athletic performance. Athletes appear to have the same risk of vitamin D deficiency and seasonal variance in status as nonathletic members of the same population, with the exception of athletes who train and compete indoors whose risk of deficiency is somewhat greater. Interventions with vitamin D supplements have had mixed results, with a positive effect on muscle function observed only in participants with insufficient status [25(OH)D <50 nmol/l]. There have been relatively few robust interventions with vitamin D supplementation in athletic populations who are vitamin D deficient, and none which have been able to establish the ideal 25(OH)D concentration for optimum performance.