Sex-specific differences in the association of magnesium intake with femoral neck bone mineral density among older adults

Background Magnesium plays a crucial role in bone metabolism, but its relationship with bone mineral density (BMD) remains complex and potentially sex-specific. This study aimed to investigate the association between magnesium intake and femoral neck BMD in older adults. Methods We analyzed data from 1,343 adults aged ≥65 years in the 2017-2020 National Health and Nutrition Examination Survey, conducted by the National Center for Health Statistics in the United States. Magnesium intake was assessed using 24-hour dietary recalls, and femoral neck BMD was measured by dual-energy X-ray absorptiometry. We employed weighted multivariate linear regression, subgroup analyses, and non-linear modeling techniques. Results The fully adjusted model (controlling for demographic, clinical, lifestyle, nutritional and biochemical factors) revealed a significant positive association between magnesium intake and femoral neck BMD (β =0.0020 g/cm 2 per 50mg/d increase in magnesium intake, 95% CI: 0.0001, 0.0039, P = 0.042). This association was stronger in women and participants with BMI >30 kg/m 2 . In men, we identified a non-linear relationship with an inflection point at 480 mg/d magnesium intake, above which the positive association diminished. Conclusions Our findings reveal complex, sex-specific relationships between magnesium intake and femoral neck BMD in older adults, highlighting the need for tailored dietary recommendations. The observed non-linear associations and threshold effects underscore the importance of optimal magnesium intake levels for bone health.