Figure 1. General types of interactions between diet, microbiota, and immune responses.

(A) (Black) The immune system shapes the microbiota, which alters the metabolism of immunomodulatory dietary factors. (Red) The microbiota metabolizes dietary substrates into immunomodulatory metabolites. (Orange) Diet influences the microbiota resulting in altered immune responses. (Blue) Dietary factors are metabolized by the host resulting in alterations to immunomodulatory microbes. (B-G) General mechanisms by which the diet, microbiome, and immune system interact to induce immunological changes: (B) Dietary derived microbial metabolites alter immune response via host receptor signaling; (C) Diet alters the fitness of immunomodulatory microbes; (D) Diet alters microbiome composition and activity, which modulates the immune response; (E) Diet alters host metabolite production which impacts immunomodulatory microbes; (F) Microbes shape host metabolism of immunomodulatory dietary factors; and (G) The immune system shapes the microbiome altering microbial metabolism of immunomodulatory dietary factors.