Association Between Dietary Tryptophan Intake and Bone Health: A Cross-Sectional Study

The relationship between dietary tryptophan intake and the risk of low bone mineral density (LBMD) has not been thoroughly evaluated. This study aimed to examine the relationship between dietary tryptophan intake and LBMD. A total of 12,003 participants aged 50 years and older with complete data on bone mineral density (BMD) and tryptophan intake from the National Health and Nutrition Examination Survey (NHANES) 2005 to 2020 were included in this cross-sectional study. The median dietary tryptophan intake among the 12,003 participants was 1822.14 mg/day, with significantly lower levels observed in individuals with LBMD compared to those with normal bone mass (1740.45 mg/day vs. 2041.39 mg/day, p < 0.001). For every 2.7-fold increase in dietary tryptophan intake, the risk of low BMD decreases by 22%. When dietary tryptophan intake was categorized into quartiles, significantly lower risks of LBMD were observed in the third [Odds Ratio (OR) = 0.68, 95% confidence interval (CI): 0.51-0.91] and fourth (OR = 0.65, 95% CI: 0.49-0.87) quartiles compared to the reference group after multivariable adjustment. Moreover, the restricted cubic spline (RCS) results revealed a negative nonlinear relationship between dietary tryptophan intake and LBMD (p for overall < 0.001, p for nonlinear < 0.05), with this correlation remaining consistent across various population subgroups and exhibiting no significant interaction according to stratification variables. Sensitivity analyses further substantiated these findings. Overall, we found that increased dietary tryptophan intake may be associated with a lower risk of LBMD among individuals aged ≥ 50 years, highlighting the importance of optimizing tryptophan nutrition for reducing osteoporosis risk.