# When Gut Microbes Run Low on Fiber, They May Start Eating You New research reveals how gut microbiota impacts health when fiber is scarce. - **Source:** [Latest Science News -- ScienceDaily](https://brifing.si/source/0eef8637-6c5b-4e79-8f5b-6c9c6b36cf16) - **Published:** 2026-08-15 - **Original article:** - **On Brifing:** https://brifing.si/s/3e06d494-97e1-41fb-93e1-c1517a8f7291 ## Multifaceted Benefits of Plant-Based Diets Plant-based diets offer wide-ranging benefits from gut health to immune function, metabolism, and cardiovascular health. A significant part of these effects stems from enhancing bacterial diversity in the gut. Fibers are broken down by microbiota, contributing to healthy metabolite production. Phytochemicals in plants also have protective effects on human health. ## Origins of Harmful and Beneficial Metabolites The PNAS study examined how plant fibers and indigestible proteins (Prifs) alter microbial metabolism. Beneficial metabolites like phenylpropionate and hippuric acid, derived from phenylalanine, support gut health, while harmful metabolites like p-cresol sulfate, from tyrosine, are linked to cancer and kidney disease. Prifs increase production of beneficial metabolites. ## The Unexpected Role of Gut Lining Using isotope tracing, researchers tracked protein digestion in mouse guts. Harmful phenols were produced when bacteria consumed host proteins from the gut lining. Beneficial phenols came almost exclusively from dietary indigestible proteins (Prifs). Fiber reduced breakdown of gut lining, lowering harmful metabolite production. ## Prifs: A New Nutrient Class The study suggests Prifs represent a new class of nutrients shaping microbiota composition with broad metabolic health implications. AbuSalim notes Prif content could soon appear on food labels below fiber. This discovery opens a new research frontier in nutritional science. ## Surprising Source of Indole Metabolites The Nature Metabolism study investigated indole metabolites' origins. Contrary to belief, these compounds can be synthesized by mammalian metabolism itself. Even after antibiotic treatment disrupted microbiota, key metabolites like indole-3-lactate remained circulating in mice and human patients. ## Links to Cancer and Neurodegenerative Diseases Indole metabolites are associated with inflammatory bowel diseases, neurodegenerative disorders, and cancer. They influence processes like cancer metastasis and anti-tumor immune responses. These findings suggest therapeutic strategies need reevaluation. ## Groundbreaking Implications for Therapy Development Both studies provide data to guide therapies targeting specific metabolites. Detailed mapping of microbiome-diet interactions paves way for personalized nutrition and treatments. Microbiota manipulation shows particular promise for chronic diseases. ## A New Paradigm for Healthy Eating Research highlights not just fiber intake but the role of indigestible plant proteins (Prifs) in diet. These findings deepen our understanding of plant-based nutrition's health impacts while proposing new standards for food industry and clinical practice. Microbiota research is ushering in a new era in nutritional science. ## Sources covering this story - https://www.sciencedaily.com/releases/2026/08/260814235842.htm — --- _Summary written by Brifing from the original reporting. Copyright in the original article belongs to its publisher; read the full piece at the link above._