Effect of Vitamin D3 Supplementation on Interleukin 6 and C-Reactive Protein Profile in Athletes.

Vitamin D3 has a preventive, anti-inflammatory effect. However, there are still few studies linking the effects of athlete training to vitamin D3 supplementation and the immune response. The study evaluated the impact of vitamin D3 supplementation on interleukin 6 (IL-6) release during physical exercise in relation to C-reactive protein (CRP) levels in healthy male athletes. Twenty-five soccer players were divided into two groups-with (GS) and without (GN) vitamin D3 supplementation in a dose of 20,000 IU twice a week for 8 wk (about 6,000 IU/d). At the baseline (T1) and at the end (T2) of the training cycle serum concentrations of 25-hydroxyvitamin D [25(OH)D], IL-6 and CRP were measured. In the GS group, we observed a significant increase in 25(OH)D concentration (p=0.004), and non-significantly increased levels (p>0.05) of IL-6 and CRP. At the baseline, CRP in the supplemented athletes who had suboptimal vitamin D3 concentration in T1 (GSO) was significantly higher than in those with an optimal baseline vitamin D3 level (GO) (p=0.028). However, in GO in T2, a non-significant trend of negative correlation (p=0.055) between 25(OH)D concentration and IL-6 level was found. In the total study group (TG), a statistically significant (p=0.021) negative correlation in T1 was observed between 25(OH)D and CRP. However, our results do not support the immune-modulatory effect of vitamin D3 supplementation in a dose of 6,000 IU/d in athletes, in relation to IL-6 production and its subsequent stimulatory effect on CRP releasing.