Sports training causes an increased load on the musculoskeletal, hormonal and immune system, which makes maintaining homeostasis in the organism more difficult. Maintaining metabolic balance in the athlete's body is important due to the necessity to obtain high physical fitness. One factor that facilitates optimization of health and increased endurance is a balanced diet. Proper nutrition enables provision of energy-giving and body-building substances as well as bioelements and vitamins, which influence metabolic processes and play regulatory functions. Vitamin D, also called calciferol, has an impact on maintaining effectiveness of the musculoskeletal system, on mineralization of bones and on increase of mass, strength and endurance of muscles. An association between vitamin D content in the organism and levels of anabolic hormones such as insulin and testosterone has been reported. A sufficient amount of calciferol is also necessary for effective functioning of the nervous system, including keeping balance and determining the reaction time. Maintaining an adequate vitamin D level in the athlete's body is also important due to its role in mobilizing the immune system and preventing infections, to which athletes are particularly prone. The positive impact of vitamin D on physical fitness of athletes shows how important it is to maintain its adequate level in the organism. Numerous studies indicate widespread occurrence of vitamin D deficiency, including among athletes. Climatic conditions and training in halls lead to limited endogenous production of this vitamin, which shows the importance of diet as a source of vitamin D. The aim of the study is to present the role of vitamin D in preservation of health, particularly endurance and physical fitness of athletes, on the basis of currently available scientific literature.