High fermented food, high fiber diet effect on human microbiome and immune system

Diet modulates the gut microbiome, which, in turn, can impact the immune system. Here, we determined how two microbiota-targeted dietary interventions, plant-based fiber or fermented foods, influence the human microbiome and immune system in healthy adults. Using a 17-week randomized, prospective study (n = 18/arm) combined with -omics measurements of microbiome and host, including extensive immune profiling, we found diet-specific effects. The high-fiber diet increased microbiome-encoded glycan-degrading CAZymes despite stable microbial community diversity. While Cytokine Response Score (primary outcome) was unchanged, three distinct immunological trajectories in high fiber-consumers corresponded to baseline microbiota diversity. Alternatively, the high-fermented food diet steadily increased microbiota diversity and decreased inflammatory markers. The data highlight how coupling dietary interventions to deep and longitudinal immune and microbiome profiling can provide individualized and population-wide insight. Fermented foods may be valuable in countering the decreased microbiome diversity and increased inflammation pervasive in industrialized society.