A higher composite dietary antioxidant index is associated with a decreased risk of subclinical hyperthyroidism in adults: evidence from epidemiological studies.

Background and objective: Thyroid dysfunction is closely related to oxidative stress, and the intake of dietary antioxidants may affect thyroid function by regulating oxidative stress. The composite dietary antioxidant index (CDAI) is used as an indicator to measure the overall antioxidant capacity of the diet by quantifying the intake of these various antioxidants. However, its association with thyroid dysfunction has not been clearly established. This study aimed to investigate the association between CDAI and thyroid dysfunction in a nationally representative sample of U.S. adults. Methods: For this research, data was drawn from the National Health and Nutrition Examination Survey (NHANES) conducted in the United States between 2007 and 2012. The study population comprised 5,956 adults age ≥ 20 years. It investigated the association between CDAI and subclinical hyperthyroidism (SCHyper) as well as other thyroid dysfunctions through multivariate logistic regression and restricted cubic spline analysis (RCS). Results: After adjusting for covariates, our research revealed that an increase in CDAI is significantly associated with a reduced risk of SCHyper [OR = 0.90, 95% CI = (0.82, 0.99), Conclusion: Higher CDAI scores were independently associated with a reduced risk of SCHyper, suggesting that dietary antioxidants may protect thyroid function by alleviating oxidative stress. These results offer new insights into the prevention and treatment of patients with SCHyper.