Dietary Modulation of Osteoporosis via Probiotics and the Gut–Bone Axis: From Mechanisms to Food Applications

Osteoporosis, a metabolic bone disorder affecting nearly one-third of women and one-fifth of men globally, poses a major public health burden. Current pharmacological treatments face limitations, driving interest in safer nutritional interventions. The gut-bone axis, through which gut microbiota modulate bone homeostasis, offers a promising target. This review synthesizes recent evidence on probiotics, including both viable and heat-inactivated strains of Lactobacillus and Bifidobacterium, as modulators of osteoporosis. Probiotics exert integrated protective effects by reinforcing intestinal barrier, balancing Th17/Treg/Breg immunity, regulating RANKL/RANK/OPG signaling, producing short-chain fatty acids, and modulating serotonin metabolism. Preclinical and clinical studies show that specific strains improve bone density and microstructure, though efficacy depends on strain, dosage, duration, and host factors. Moreover, heat-inactivated forms and postbiotics offer stability advantages. Future development of synbiotics, next-generation probiotics, and functional foods tailored to specific matrices, along with personalized strategies, promises effective dietary interventions for bone health.