Associations between dietary index for gut microbiota and bone health outcomes.

UNLABELLED: Adults who consumed more foods or nutrients that support healthy gut bacteria had fewer fractures, less osteoporosis, and slightly higher bone density. This study suggests that gut-friendly eating habits may be linked to better bone health and should be explored further.

PURPOSE: Gut microbiota has been implicated in bone health and may be modulated by habitual diet. However, associations between dietary components influencing gut microbiota composition and/or function-as captured by the dietary index for gut microbiota (DI-GM)-and bone health outcomes have not been previously investigated. The present cross-sectional study was performed to investigate the associations between DI-GM and fracture (primary outcome), as well as osteoporosis and bone mineral density (BMD) at the femoral neck and lumbar spine (secondary outcomes).

METHODS

Data from 9385 adults aged ≥ 20 years in the National Health and Nutrition Examination Survey (NHANES) 2009-2020 were analyzed. DI-GM scores (range: 0-13) were calculated from two 24-h dietary recalls based on the intake of microbiota-relevant dietary components, including beneficial foods such as fiber-rich plants and fermented dairy products, and unfavorable components such as red and processed meats, refined grains, and high-fat diets. Higher scores reflected more microbiota-supportive diets. Fracture history and osteoporosis status were self-reported, with osteoporosis additionally identified using femoral neck BMD. BMD was measured at the femoral neck and lumbar spine using dual-energy X-ray absorptiometry. Multivariable regression models assessed associations between DI-GM and each bone health outcome, adjusting for relevant covariates.

RESULTS

Each 1-unit increase in DI-GM was associated with lower odds of fracture (OR = 0.90; 95% CI: 0.87-0.93) and osteoporosis (OR = 0.94; 95% CI: 0.92-0.96), with consistent associations across fracture sites and sexes. DI-GM was positively associated with femoral neck BMD (β for each 1-unit increase = 0.003 g/cm2; 95% CI: 0.001-0.005), particularly among men. No association was observed with lumbar spine BMD in the overall (β for each 1-unit increase = -0.001; 95% CI: -0.004 to 0.001) or sex-stratified analyses.

CONCLUSIONS

In this nationally representative sample of U.S. adults, greater adherence to a dietary pattern characterized by microbiota-relevant components, as reflected by higher DI-GM scores, was associated with lower prevalence of fracture and osteoporosis, and modestly higher femoral neck BMD. These findings suggest a potential link between diet-microbiota interactions and skeletal health, which warrants further investigations in longitudinal studies.