Circulating cytokine concentrations are not altered by supplemental vitamin D in knee osteoarthritis: A pilot study

The purpose of this investigation was to identify if raising serum 25-hydroxyvitamin D (25(OH)D) through vitamin D supplementation modulates circulating cytokine concentrations in subjects with knee osteoarthritis (OA). This study consisted of a randomized, double-blind, placebo-controlled study design. Twenty-nine subjects with knee OA were randomly assigned to one of two oral-supplement groups: 1) placebo (PL; n = 15) or 2) vitamin D (VD; n = 14; 4000 IU/d, cholecalciferol). Supplements were taken daily for 84-d. Serum 25(OH)D and cytokine concentrations were measured in fasting blood samples obtained prior to (i.e., at Baseline (Bsl)), during, and following supplementation. At Bsl, circulating interleukin (IL)-10 and IL-12 concentrations were significantly (all p < 0.05) higher in subjects above (i.e., ≥26.3 ng/mL, n = 14) compared to below (i.e., <26.3 ng/mL, n = 15) the median serum 25(OH)D concentration prior to supplementation. Following supplementation, serum 25(OH)D concentrations were significantly (p < 0.05) increased (~45%) in the VD group and circulating cytokine concentrations were not significantly different between groups (i.e., PL vs VD). Based on these findings, we conclude that higher serum 25(OH)D concentrations at baseline associate with higher serum IL-10 and IL-12 concentrations in subjects with knee OA. However, raising serum 25(OH)D concentrations with vitamin D supplementation did not perturb serum cytokine concentrations. ClinicalTrials.gov identifier: NCT04121533.