Dietary index for gut microbiota and its protective role against osteoporosis: Evidence from NHANES 2007 to 2018

Distortions in gut microbiota homeostasis may contribute to abnormal bone metabolism and osteoporosis. This study aimed to examine the association between the dietary index for gut microbiota (DI-GM) and osteoporosis among U.S. adults, identify key dietary components, and develop a clinically applicable risk prediction model incorporating dietary and clinical factors. We conducted a cross-sectional analysis of 9065 adults. DI-GM was calculated from the dietary intake data, and osteoporosis was the primary outcome. Weighted multivariable logistic regression models were used to evaluate the association between DI-GM and osteoporosis, and odds ratios (ORs) with 95% confidence intervals (CIs) were calculated. Additionally, least absolute shrinkage and selection operator regression was applied to identify critical dietary components. Finally, a prediction model integrating clinical and nutritional factors was developed and evaluated using receiver operating characteristic curve analysis. Each unit increase in DI-GM reduced the risk of osteoporosis by 10% (adjusted OR = 0.90, 95% CI: 0.83-0.99). A higher intake of DI-GM-beneficial components was also associated with reduced osteoporosis risk (OR: 0.88; 95% CI: 0.79-0.98). Least absolute shrinkage and selection operator highlighted soy, fermented dairy, and processed meat as the most influential dietary factors; higher intake of soybeans and fermented dairy was associated with a decreased risk of osteoporosis, whereas higher processed meat intake was associated with an increased risk. The prediction model demonstrated good discrimination (area under the curve = 0.757). A higher DI-GM was associated with a reduced risk of osteoporosis, and specific dietary components may drive this association. The proposed model may support individualized dietary risk stratification and prevention strategies for populations with an elevated osteoporosis risk.