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 to 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 employed 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, 95% 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, 95% CI=0.23-0.87, P=0.020) and high (T3, OR=0.19, 95% CI=0.09-0.39, P<0.001) dietary vitamin E intake being associated with a lower prevalence of SCH. Additionally, moderate (T2, OR=0.59, 95% CI=0.37-0.93, P=0.024) and high (T3, OR=0.52, 95% 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.