Dr. Gabi Fragiadakis

Several studies have established links between diet and the microbiota, and that link the microbiota and host health. We performed a dietary intervention to ask (i) to what extent can the microbiota be altered over the course of weeks using diet in healthy adults, and (ii) do these changes result in an improvement in the immune system. We selected two diets that have been implicated in affecting the microbiota: a diet high in dietary fiber, complex carbohydrates that can serve as substrates for the microbiota and have been shown to induce rapid changes in the gut microbiome; and a diet high in fermented foods, which are rich in living microbes and have been explored as treatments for inflammatory conditions and in microbial dysbiosis. We longitudinally tracked both the microbiota and the immune system, using technologies that provide a systems-level view of both microbial and immune function. We found that participants consuming fermented foods had an increase in microbial diversity and an improvement in immune status, as defined by decreases in inflammatory cytokines, decreases in immune signaling at steady-state, and an increase in signaling capacity ex vivo. In contrast, participants consuming high-fiber diets exhibited varied response both in changes to the microbiota and in immune state. This study is a proof-of-concept for longitudinal, systems-level microbiota and immune profiling in humans, and can serve as a template for future studies toward untangling the complex interactions between diet, the microbiota, and the immune system.