PURPOSE: To evaluate the associations between protein intake and fractures risk in a large population-based cohort. METHODS: We conducted a prospective population-based study of UK Biobank. Participants aged 40-69 who completed the Oxford WebQ dietary questionnaire at least once were included. Exposures were percentage of energy provided by protein and its components (animal and vegetable protein). Participants were categorized into quintiles based on these exposures. The primary outcome was composite fracture, and secondary outcomes included osteoporotic and hip fractures, defined by ICD-10 codes. We used Cox proportional hazard models and restricted cubic splines (RCS) to assess the association between exposure and outcomes, as well as their dose-response relationships. RESULTS: This study included 132,807 participants (mean [SD] age, 56.8 [8.0] years
68,769 [51.8 %] female). During a median follow-up of 12.4 years, 6,673 composite fractures, 4,496 osteoporotic fractures and 930 hip fractures occurred. Regarding protein intake, compared to the lowest quintile (Q1), individuals in the highest quintile (Q5) had significantly lower risks of composite fracture (HR 0.82, 95 % CI 0.75-0.90), osteoporotic fracture (HR 0.81, 95 % CI 0.72-0.91) and hip fracture (HR 0.63, 95 % CI 0.49-0.82). Similar results were observed for animal and vegetable protein intake. RCS revealed a negative linear dose-response relationship between protein intake and fractures risk. CONCLUSION: Increased protein intake can significantly reduce the risk of fractures and may serve as an important dietary strategy for promoting bone health.