Abstract
Vitamin D does not only influence the musculoskeletal health and mineral homeostasis but it also affects cardiovascular, endocrine, nervous, immune and mental functions, thus it is of considerable importance for both physically active people and elite athletes. However, vitamin D deficiency is common worldwide and results from inadequate endogenous skin synthesis (insufficient ultraviolet B exposure) and diet. To improve the vitamin D status elite athletes often travel to lower latitude during winter. The aim of the study was to evaluate the seasonal vitamin D status in Polish elite athletes according to the sun exposure and oral supplementation. Serum concentration of 25-hydroxyvitamin D (25(OH)D) was measured in the years 2010–2014 in 409 elite athletes, who were divided into the following groups: OUTD—outdoor sports, represented by track and field athletes, who trained in Poland; IND—weightlifters, handball and volleyball players who trained indoors in Poland; SUN—track and field athletes who trained during Polish winter in lower latitude with high sunshine exposure; SUPL—track and field athletes who trained in Poland, had an inadequate vitamin D status (25(OH)D < 30 ng/ml) and were supplemented orally. Inadequate Vitamin D status was observed in 80% of OUTD and 84% of IND athletes in winter, whereas in summer the values amounted to 42% and 83%, respectively. The athletes exposed to sun in winter had significantly higher vitamin D concentration than OUTD group. Oral supplementation improved vitamin D concentration by 45%, whereas winter sun exposure caused its increase by 85%. Except for a few summer months an inadequate status of vitamin D was found in the majority of Polish elite athletes, with the deficiency level being similar to the one observed in non-athletic population. The most serious deficiency was observed in indoor disciplines. Adequate vitamin D status can be achieved by both increased sun exposure, especially in winter, and oral supplementation. Athletes should therefore routinely assess their vitamin D status and be educated how to approach their sunlight exposure, diet and supplementation.
Highlights
Inadequate vitamin D status is common worldwide and might impact both the athletes’ health and performance [1,2,3,4,5]
The dietary source of vitamin D is poor and approx. 90% of its supply originates from sunshine-induced skin synthesis which correlates with latitude, season of the year, time of day, age, skin melanine content and use of sun screens [4,8]. 25-hydroxyvitamin D– 25(OH)D is the best available biomarker of vitamin D status [7,8,16] there is no consensus about its minimal level required in blood
The following groups were distinguished for the purpose of the analysis (Table 1): OUTD— outdoor sports, represented by track and field athletes, who trained in Poland, at the latitude of 49–54° N; IND—weightlifters, handball and volleyball players who trained mostly indoors in Poland; SUN—track and field athletes who trained during Polish winter (Jan-Mar) in The Republic of South Africa (RSA), at the latitude of 27° S and in April on Tenerife, at the latitude of 28° N, and had their samples taken within 1–4 weeks after their return to Poland
Summary
Inadequate vitamin D status is common worldwide and might impact both the athletes’ health and performance [1,2,3,4,5]. Low vitamin D status, especially in winter [3,5,17,18,19,20], has been identified in more than a billion people around the world (58–90% of North American and European population) as a consequence of urbanization, indoor lifestyle and sun protection strategies aimed at decreasing the risk of skin cancer incidence. This can be prevented by oral supplementation, food fortification and sensible sun exposure
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