Composite dietary antioxidant index in predicting chronic kidney disease risk: Findings from NHANES 1999 - 2018

Chronic kidney disease (CKD) poses a significant global health burden, with oxidative stress implicated in its pathogenesis. The composite dietary antioxidant index (CDAI), integrating multiple dietary antioxidants, may offer a novel approach to CKD risk assessment, yet evidence remains limited.

This study aimed to evaluate the association between CDAI and CKD risk in a nationally representative U.S.

Cross-sectional data from 24,202 adults in NHANES (1999 - 2018) were analyzed. CDAI was calculated from six dietary antioxidants (vitamins A/C/E, zinc, selenium, β-carotene). CKD was defined by estimated glomerular filtration rate (eGFR) < 60 mL/min/1.73m² or UACR ≥ 30 mg/g. Multivariable logistic regression, restricted cubic splines (RCS), and subgroup analyses were employed to assess associations, adjusted for demographics, lifestyle, comorbidities, and laboratory parameters.

Participants in the highest CDAI quartile (Q4) had a 27% lower CKD risk (adjusted OR = 0.73, 95% CI: 0.62 - 0.87, p < 0.001) vs. Q1, with a dose-dependent relationship (p-trend < 0.001). RCS revealed nonlinear effects, with steep risk reduction at CDAI < 10 and plateauing at CDAI > 20. Subgroup analyses showed stronger inverse associations in women, older adults (≥ 65 years), and individuals with diabetes or cardiovascular disease (p-interaction < 0.05). Mediation analysis indicated direct effects of CDAI, independent of traditional risk factors.

Higher CDAI levels were independently associated with reduced CKD risk, particularly in high-risk subgroups. These findings support the potential role of dietary antioxidants in CKD prevention, warranting further prospective validation.