Dietary Index for Gut Microbiota and Osteoporosis Risk in Chinese Postmenopausal Women: A Case–Control Study

Background: Diet influences bone health through modulation of gut microbiota. The current study aimed to assess the association between the dietary index for gut microbiota (DI-GM) and osteoporosis in Chinese populations. Methods: We conducted a case-control study among 500 postmenopausal Chinese women (250 osteoporosis and 250 controls). Controls were postmenopausal women matched or frequency-matched to cases on key characteristics (eg, age ± 2 years, time since menopause) who had BMD measurements within the normal or osteopenic range (ie, T-score > − 2.5) at the same skeletal sites. The DI‑GM score was calculated based on 14 components, yielding a total possible score range of 0 to 14. The DI‑GM was analyzed as both a continuous variable and as categorical variables (0– 3, 4, 5, ≥ 6). Logistic regression models adjusted for confounders were used to examine associations. Results: In the fully adjusted logistic regression, when DI-GM was analyzed as a continuous variable, the association with osteoporosis was not statistically significant (OR per 1-point increase: 0.96; 95% CI, 0.92– 1.01). However, the analysis of categorical variables revealed women with DI-GM ≥ 6 had significantly lower odds of osteoporosis compared with scores 0– 3 (OR 0.59; 95% CI, 0.36– 0.97). Associations were stronger among women with BMI < 25 kg/m 2 and serum 25(OH) D ≥ 20 ng/mL, although the interactions were not statistically significant (p > 0.05). Conclusion: A high DI-GM score is significantly associated with a lower prevalence of osteoporosis in Chinese postmenopausal women, particularly when comparing the highest versus the lowest score categories.