Higher dietary zinc intake increases the risk of autoimmune thyroiditis

Background: Autoimmune thyroiditis (AIT), encompassing Hashimoto's thyroiditis (HT), is a prevalent chronic autoimmune disorder characterized by lymphocytic infiltration and the presence of anti-thyroid antibodies. It is the primary cause of primary hypothyroidism and affects women more frequently than men. Nearly 95% of individuals with HT exhibit thyroid peroxidase antibodies or thyroglobulin antibodies. Dietary factors, including vitamins and trace elements such as zinc, play a significant role in thyroid health; yet, clinical guidelines lack explicit dietary recommendations for AIT.

Methods: This study investigates the relationship between dietary zinc intake (Zinc) and AIT using data from the 2007-2008 National Health and Nutrition Examination Survey. A total of 5467 participants were analyzed, including 273 individuals with AIT and 5194 without AIT. Clinical characteristics, dietary Zinc, and other relevant variables were assessed. Multivariate logistic bidirectional stepwise regression analysis was conducted to identify independent risk factors for AIT, and a risk prediction model was developed.

Results: The prevalence of AIT was 5%. Individuals with AIT were older, had a higher proportion of females, and showed elevated levels of various biomarkers, including zinc. Dietary Zinc was significantly higher in the AIT group (22.6 mg vs. 15.3 mg, P < .001). The regression analysis identified dietary Zinc, along with other factors, as an independent risk factor for AIT. The risk prediction model, including zinc, demonstrated a better performance (area under the curve = 0.8) compared to the model without zinc.

Conclusion: The findings indicate that higher dietary Zinc is positively correlated with the risk of AIT and serves as an independent risk factor. Excessive Zinc may disrupt immune balance, potentially increasing the risk of autoimmune diseases. These results suggest that dietary Zinc should be carefully considered in the management of AIT, and further research is needed to explore the causal relationship and determine safe zinc consumption levels to avoid increasing the risk of autoimmune diseases.