During the 13th World Congress on Probiotics, Prebiotics and New Foods, held recently in Rome (italy) Microbiomepost sat down with Mahesh Desai, group leader of the Eco-Immunology and Microbiome team at the Luxembourg Institute of Health and adjunct associate professor in ‘Gut microbiome in health and disease’ at the University of Southern Denmark to discuss about his research in nutrition and gut microbiome.

Dietary fiber plays a crucial role in maintaining gut barrier integrity by modulating the activity of mucin-degrading bacteria. Previous mechanistic studies in mouse models have shown that fiber deprivation promotes microbial erosion of the colonic mucus layer, increasing susceptibility to enteric infections and chronic inflammatory conditions. To translate these findings to humans, we conducted a crossover dietary intervention in healthy participants, comparing high-fiber (40 g/day) and low-fiber (20 g/day) diets. 

Across approximately 900 days of dietary records, coupled with extensive stool and blood sampling, we observed that reduced fiber intake was consistently associated with the enrichment of mucin-degrading bacteria and their cross-feeding partners, which we define as “low-fiber biomarkers.” These microbial signatures exhibited limited growth on polysaccharide substrates and were reproducibly linked to inflammatory, metabolic, autoimmune, and neurological diseases in comparative datasets. Mechanistic validation in a mouse model of colitis confirmed that one key biomarker, Ruminococcus torques, exacerbates inflammation and mucus erosion under low-fiber conditions. Collectively, our findings highlight that insufficient fiber consumption in humans promotes a microbial signature characterized by mucin-degrading and opportunistic taxa, with potential implications for the development of a wide range of chronic diseases.