Vitamin E Intake and Prevalence Rates of Thyroid Dysfunction and Autoimmune Thyroiditis: A Cross-Sectional Analysis of NHANES Data.

Background: Thyroid disorders are associated with various dietary factors and nutritional elements. The aim of this study was to investigate the relationships between dietary vitamin E intake and the prevalence of thyroid dysfunction and thyroid antibody positivity using data from the National Health and Nutrition Examination Survey (NHANES) database. Methods: Data from the NHANES database collected between 2007 and 2012 were analyzed. A total of 7,773 nonpregnant adults without preexisting thyroid diseases and possessing complete thyroid and vitamin E data were included in the study. The participants were categorized into tertiles based on their dietary vitamin E intake: the lowest group (T1: ≤4.53 mg), the intermediate group (T2: 4.54-8.10 mg), and the highest group (T3: ≥8.11 mg). We used a complex multistage probability sampling design in conjunction with R software. We compared thyroid indices, the prevalence of overt and subclinical hyperthyroidism or hypothyroidism, and the occurrence of thyroid antibody positivity among the three groups based on vitamin E intake. Weighted multinomial logistic regression was used to assess the association between dietary vitamin E intake and thyroid disorders. Restricted cubic splines (RCSs) were used to explore potential nonlinear associations. Results: The prevalence rates of subclinical hypothyroidism (SCH) were 3.63%, 3.07%, and 1.85% in T1, T2, and T3, respectively, indicating a decreasing trend (P-trend = 0.013). In the general population, high vitamin E intake (T3) was significantly associated with a lower prevalence of SCH (OR = 0.28, CI = 0.15-0.54, p < 0.001). Subgroup analysis revealed a more pronounced protective effect in males, with both moderate (T2, OR = 0.45, CI = 0.23-0.87, p = 0.020) and high (T3, OR = 0.19, CI = 0.09-0.39, p < 0.001) dietary vitamin E intake being associated with a lower prevalence of SCH. In addition, moderate (T2, OR = 0.59, CI = 0.37-0.93, p = 0.024) and high (T3, OR = 0.52, CI = 0.36-0.75, p < 0.001) dietary vitamin E intake was associated with a lower prevalence of autoimmune thyroiditis (AIT) in males. However, no significant association was observed among females. Conclusion: The findings of this study suggest that a higher intake of vitamin E is associated with lower prevalence rates of SCH and autoimmune thyroiditis among males.