Dietary fibre and the gut microbiome: implications for glucose homeostasis

Despite long-standing evidence linking dietary fibre intake to improved glycaemic control and reduced chronic disease risk, most individuals fail to meet recommended intake levels. As interest grows in the gut microbiota's role in mediating fibre's health effects, this review evaluates recent human intervention trials to assess whether dietary fibre improves glucose homeostasis through microbiota-dependent mechanisms.

Nine recent randomised controlled trials (RCTs) have examined the effects of dietary fibre on glycaemic markers and gut microbiota, primarily in individuals at risk of or diagnosed with metabolic disease. Five studies reported improvements in glycaemic outcomes such as fasting glucose, insulin, or HOMA-IR. Microbial responses were inconsistent, with variable effects on diversity and composition. Notably, improvements in markers of gut barrier integrity and systemic inflammation were consistently observed in studies including these as mechanistic outcomes.

Although dietary fibre may enhance glycaemic control and modulate the gut microbiota, effects vary by fibre type, dose, population, and study design. Markers of gut barrier integrity and inflammation appear to be more reliable indicators of benefit compared with the assessments of gut microbial composition. Future trials should prioritise healthy populations to explore the potential of dietary fibre to maintain metabolic health.