Links between bone fractures and the gut microbiota.

As populations age worldwide, the incidence of fractures is increasing, leading to considerable disease burden and increased health-care costs. Bone mineral density (BMD), bone quality and muscle function are major contributors to fracture risk, with muscle function having a critical role in preventing falls. The gut microbiota is well established as a regulator of these parameters in rodents, with the immune system and short-chain fatty acids acting as key mediators of these effects. First-generation probiotic interventions have demonstrated modest effects on BMD in clinical trials. In humans, the association between the gut microbiota and muscle mass, muscle function and fracture risk seems to be more robust than the correlation between gut microbiota and BMD. Future research should prioritize the development of more targeted gut microbiota-based interventions, including second-generation probiotics, personalized dietary strategies, synbiotics, postbiotics and species-specific antibiotics with the potential to enhance both BMD and muscle function, thereby reducing risk of fractures.