Table 3.

The association between 25(OH)D levels and inflammatory cytokines and the effect of vitamin D supplementation on inflammatory cytokines in humans.

The Association between 25 ( OH ) D Levels and Inflammatory Cytokines
Study Design, n	Results
A cross-sectional population-based study, 281 [53]	- A negative association between plasma IL-6 and TNF-α levels and serum 25(OH)D concentration in normal-weight participants - A negative association between plasma adiponectin level and serum 25(OH)D concentration in overweight participants
Post hoc analysis from 1-year lifestyle intervention program, 113 men [54]	- An increase in 25(OH)D levels were associated with a decrease in leptin levels after adjustment for changes in adiposity - No association between changes in 25(OH)D levels and changes in adiponectin levels
The Effect of Vitamin D Supplementation on Inflammatory Cytokines
Study design, n	Type of vitamin D, dose, duration	Results
RCT, subcutaneous abdominal adipose tissue from 40 participants with obesity and vitamin D deficiency (25(OH)D < 20 ng/mL) [25]	Vitamin D3 7000 IU/day vs. placebo, 26 weeks	- No differences in the changes in MCP-1, IL-6, IL-8, and adiponectin levels from baseline between the 2 groups - No differences in the expression levels of MCP-1, IL-6, and IL-8 before and after treatment with either placebo or vitamin D
RCT, 332 participants with overweight and obesity [55]	Vitamin D3 40,000 IU/week vs. 20,000 IU/week vs. placebo, 1 year	- A non-significant decrease in IL-6 (p = 0.08) and a significant increase in CRP (p < 0.05) in the vitamin D group when compared with the placebo group - No effect of vitamin D supplementation on TNF-α levels
A systematic review and meta-analysis of 13 RCTs, 1955 participants with obesity or overweight [56]	Vitamin D3 700–200,000 IU/day or vitamin D2 150,000 IU at 0 and 12 weeks, duration 4–156 weeks (mean 41 weeks)	- No significant reduction in CRP, TNF- α, and IL-6 levels after receiving vitamin D supplementation
A systematic review and meta-analysis of 13 RCTs, 875 participants with type 2 diabetes [57]	Vitamin D2 or D3 20–6000 IU/day or 25,000 or 50,000 IU/week, duration 8–52 weeks (median 12 weeks)	- A significant decrease in CRP in the vitamin D group when compared with no vitamin D treatment (p = 0.005) - No effects of vitamin D supplementation on TNF-α and IL-6

25(OH)D: 25-hydroxyvitamin D; CRP: C-reactive protein; IL-6: interleukin 6; IL-8: interleukin 8; MCP-1: monocyte chemoattractant protein-1; RCT: randomized-controlled trial; TNF-α: tumor necrosis factor-alpha.