Association between the dietary index for gut microbiota and fracture prevalence among women aged 50 years and older: a NHANES-based study with a preliminary exploratory pilot analysis

IntroductionGut microbiota has been implicated in bone metabolism, but whether a diet supporting gut microbial health is associated with fracture prevalence in older women remains unclear. This study aimed to examine the association between the dietary index for gut microbiota (DI-GM) and fracture prevalence in women aged 50 years and older.MethodsWe analyzed cross-sectional data from five NHANES cycles, including 6,318 women aged 50 years and older (mean age 63.8 ± 9.6 years). DI-GM scores were derived from 24-h dietary recalls based on 13 dietary components. Self-reported hip, wrist, or spine fracture was the outcome (863 women, 13.7%). Bone mineral density (BMD) was measured by dual-energy X-ray absorptiometry. Weighted logistic regression and exploratory mediation analyses were performed.ResultsHigher DI-GM scores were associated with lower odds of fragility fracture (OR = 0.93, 95% CI: 0.88–1.00, p = 0.035) and any fracture (Model 3: OR = 0.96, 95% CI: 0.92–0.99, p = 0.045). Neither femoral neck nor spinal BMD significantly mediated these associations. In a small exploratory pilot cohort (n = 12), DI-GM scores were positively correlated with spinal BMD (R = 0.82, p = 0.0011).DiscussionHigher DI-GM scores were associated with lower fracture prevalence in women aged 50 years and older, although BMD did not significantly mediate this association. Given the cross-sectional design and the small pilot sample, these findings should be considered exploratory and require confirmation in larger prospective studies.