Modulation of select immune responses by dietary capsaicin

Capsaicin (CAP) is the spicy principle of hot peppers that has been used as a food additive, preservative, and medicine. In this study, we investigated the effect of dietary CAP on immune status and selected immune responses. BALB/c mice were divided into 5 groups and fed diets with either 0, 5, 20, 50 or 100 ppm CAP for 3 weeks. The parameters measured with lymphocytes included mitogen-induced proliferation, plaque-forming cell number, and total serum immunoglobulin levels. In spleen cells of mice fed 20 ppm CAP there was a greater T-cell mitogen induced, lymphocyte proliferative response. In addition, the number of antibody-producing B cells and serum IgG and IgM levels increased in mice fed 20 ppm CAP as compared to the control with no CAP. The effect of dietary CAP on macrophage activity was assessed by phagocytosis and tumor necrosis factor-alpha (TNFα) production. Dietary CAP had no effect on phagocytic activity by peritoneal macrophages, but the levels of secreted TNFα increased in the groups fed 20 ppm CAP compared to the control. These results suggest that dietary CAP may differentially enhance immune status as well as select immune functions. That is in contrast with previous studies that show immunosuppression observed after CAP injection.