Muscular effects of vitamin D in young athletes and non-athletes and in the elderly.
Hormones (Athens). 2016 Oct;15(4):471-488. doi: 10.14310/horm.2002.1705.
Koundourakis NE1, Avgoustinaki PD1, Malliaraki N1, Margioris AN1.
Department of Clinical Chemistry, School of Medicine, University of Crete, Heraklion, Greece.
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Muscles are major targets of vitamin D. Exposure of skeletal muscles to vitamin D induces the expression of multiple myogenic transcription factors enhancing muscle cell proliferation and differentiation. At the same time vitamin D suppresses the expression of myostatin, a negative regulator of muscle mass. Moreover, vitamin D increases the number of type II or fast twitch muscle cells and in particular that of type IIA cells, while its deficiency causes type IIA cell atrophy. Furthermore, vitamin D supplementation in young males with low vitamin D levels increases the percentage of type IIA fibers in muscles, causing an increase in muscular high power output. Vitamin D levels are strongly associated with exercise performance in athletes and physically active individuals. In the elderly and in adults below the age of 65, several studies have established a close association between vitamin D levels and neuromuscular coordination. The aim of this review is to appraise our current understanding of the significance of vitamin D on muscular performance in both older and frail individuals as well as in younger adults, athletes or non-athletes with regard to both ordinary everyday musculoskeletal tasks and peak athletic performance.