Anti-inflammatory effects of dietary vitamin D₃ in patients with multiple sclerosis

To assess the effects of dietary vitamin D₃ on proinflammatory (interleukin-17A [IL-17A] and IL-6) and anti-inflammatory (IL-10) cytokines.

Our study was conducted on 75 participants who were divided into 3 groups: multiple sclerosis participants (MSPs, n = 25), first-degree relative participants (FDRPs, n = 25), and healthy participants (HPs, n = 25). All groups received 50,000 IU vitamin D₃/wk for 8 weeks. Serum 25-(OH) vitamin D₃ levels and messenger RNA (mRNA) expression levels of ILs were determined using electrochemiluminescence assay and real-time PCR, respectively.

Vitamin D₃ affected the levels of IL-17A, IL-10, and IL-6 among the 3 groups (p < 0.001 for all). Levels of IL-17A (MSPs: fold change [FC] = 5.9, p = 0.014; FDRPs: FC = 5.2, p = 0.006; HPs: FC = 4.2, p = 0.012) and IL-6 (MSPs: FC = 5.6, p = 0.003; FDRPs: FC = 5.5, p = 0.002; HPs: FC = 5.1, p < 0.001) were downregulated after vitamin D₃ treatment. In addition, levels of IL-10 (MSPs: FC = 6.2, p = 0.005; FDRPs: FC = 4.6, p < 0.001; HPs: FC = 5.2, p < 0.001) were upregulated after 8 weeks.

Although supplementation with vitamin D₃ reduced the mRNA expression levels of IL-17A and IL-6, it increased the mRNA expression level of IL-10 in all groups. However, these effects were more considerable in the MSP group than in the other groups. Of interest, in a deficiency state of serum vitamin D3, IL-17A expression had a positive feedback effect on the expression of IL-6. Conversely, in the sufficient state, IL-10 expression had a negative feedback effect on the expression of IL-17A and IL-6.