[Impact of Vitamin D in Sports: Does Vitamin D Insufficiency Compromise Athletic Performance?].

Vitamin D is essential for calcium homeostasis and regulates the expression of over 900 genes. It thereby influences musculoskeletal health and function. Additionally, multiple other effects were observed through the detection of vitamin D receptors (VDR) in numerous tissues of the human body.  We reviewed the literature regarding evidence of the impact of vitamin D on musculoskeletal health and peak athletic performance.  It is well known that there is a high prevalence of vitamin D deficiency in the average European population. This article confirmed the same for athletes in different disciplines. Therefore, vitamin D deficiency and its effects are relevant for competitive sports. The surprisingly high prevalence of inadequate vitamin D levels depends on the geographic location, the time of day and year, local climate conditions, and sports disciplines (indoor vs. outdoor). Based on the analysed literature, we found several correlations between 25-OH-D3 serum levels and different aspects of competitive sports. A serum level ≥ 30 ng/ml provides sufficient mineralisation of non-mineralised bone matrix and is therefore crucial for skeletal health. Furthermore, this concentration was positively correlated with an accelerated regeneration of muscular force. Levels above 40 ng/ml provided a protective effect on the development of stress fractures. Researchers suspect that levels above 50 ng/ml are required for athletes to achieve maximal physical performance. While there is an ongoing discussion amongst researchers regarding beneficial effects of such high levels, it is well known that blood levels lower than 30 ng/ml lead to mineralisation defects in bone (rickets, osteomalacia) and muscular function (reversible myopathy).  This review suggests that athletes should have an evaluation of vitamin D-dependent calcium homeostasis based on laboratory tests of 25-OH-D3, calcium, creatinine, and parathyroid hormone. In case of vitamin D insufficiency, normal blood levels of ≥ 30 ng/ml may be restored by optimising the athlete's lifestyle and, if appropriate, oral substitution of cholecalciferol. This concentration is associated with a protective effect and enhancement of physical performance. Consequently, it is a requirement for restoring and maintaining musculoskeletal health and athletic performance.