Vitamin D deficiency is more common in the obese population, in whom there is an inverse relationship between serum vitamin D levels and the degree of obesity. Vitamin D has also been shown to skew T cells toward a less inflammatory state. For instance, 1,25(OH)2D3 decreases T cell-mediated IFN-γ production while increasing IL4 production [42, 43]. Both the generation and immunosuppressive capacity of Foxp3 + CD4+ regulatory T cells are increased by 1,25(OH)2D3 . Moreover, recent studies showed that production of the inflammatory cytokine IL17 by T cells is prevented by 1,25(OH)2D3 [43, 45]. In line with these results, other groups have documented that the development of Th17 cells is negatively modulated by 1,25(OH)2D3 . Production of IL21, IL22 and IL17 is also inhibited by physiologically relevant doses of 1,25(OH)2D3 in Th17-skewed T cells; this evidence suggests that principal changes in transcription are driven by the vitamin D receptor-transcription factor complex .