Prevalence of vitamin D deficiency amongst soccer athletes and effects of 8 weeks supplementation.

Background: High prevalence of vitamin D deficiency is well known around the world in risk populations. Although less is known about the athletic population, some studies report vitamin D deficiency amongst athletic population and adequate vitamin D levels are crucial for athletic population as they can prevent injuries such as stress fractures and might even have ergogenic effects for example on muscle function. The main objectives were to evaluate the basal serum levels of 25(OH)D and calcium in professional soccer athletes on the latitude 40°N, to evaluate the effects in 25(OH)D and calcium serum levels following supplementation of 1667 IU/day of cholecalciferol during a period of 8 weeks and evaluate eventual toxicity arising from it.

Methods: Twenty-eight professional athletes were evaluated according to the skin type. Basal serum levels of 25(OH)D and calcium were evaluated during winter months. Athletes were then supplemented with cholecalciferol 25.000 IU every two weeks. Serum levels of 25(OH)D and calcium were evaluated after supplementation.

Results: 25(OH)D initially ranged between 9.9 ng/mL and 32.9 ng/mL with a median of 19.2 IQR 7.24 ng/mL. A statistically significant inverse correlation exists between vitamin D deficiency and the Fitzpatrick Scale (ρ=-0.555 P=0.003). After 8 weeks, 25(OH)D ranged between 10.6 ng/mL and 43.4 ng/mL with a median of 33.2 ng/mL IQR 6.1 ng/mL. We verified a statistically significant increase of serum 25(OH) D levels (11.74±5.988; CI 95% [9,02; 14,47]; P<0.001. In addition, there was a statistically significant reduction of calcium: -0.36±0.457; CI 95% [- 0.57; -0.15]; P=0.002.

Conclusions: Professional athletes have a high prevalence of vitamin D deficiency. Supplementation with cholecalciferol in winter months during 8 weeks is safe and effective in raising 25(OH)D serum levels. However, it may not be sufficient for athletes to reach adequate vitamin D levels.