There is increasing evidence that vitamin D (VitD) supplementation may reduce inflammation in individuals with multiple sclerosis (MS). The aim of this study was to evaluate the effect of different doses of VitD on selected markers of inflammation in patients with relapsing-remitting MS (RRMS). Participants were divided depending on the supplemented dose of VitD into a high-dose (2000 IU/d; HD) group and a low-dose (15,960 IU/month; LD) group (n = 23 and n = 29, respectively). The concentration of 25(OH)D and the levels of CXCL16, PTX3, ALCAM, IL-1RA, and OPG were measured initially and after six months of VitD supplementation in blood serum. A significant increase in the concentrations of CXCL16, PTX3, and OPG was observed during the study (p = 0.02, p = 0.01, and p < 0.01, respectively). Furthermore, a higher increase in PTX3 and OPG in the LD group was observed (p = 0.04 and p = 0.03, respectively). A significant positive correlation was observed between the 25(OH)D serum concentration and PTX3 (R = 0.28, p < 0.05) and OPG (R = 0.28, p < 0.05) only at the beginning of the study. In patients with RRMS, such doses of VitD might be too low to induce obvious beneficial effects on the pro-inflammatory and inflammatory balance.
Keywords: immune system; inflammation; multiple sclerosis; supplementation; vitamin D.