Objective:

To identify dietary and metabolic factors associated with Hashimoto’s thyroiditis (HT) risk and evaluate whether tuber-associated metabolites causally influence HT susceptibility.

Approach:

• Study Design: Cross-sectional analysis of 7,878 community-dwelling adults (≥40 years) from the REACTION cohort in Dalian, China.
• Data Collection: Screened 49 variables including dietary intake, lifestyle behaviors, anthropometrics, and metabolic parameters using logistic regression.
• Mendelian Randomization: Analyzed eight tuber-associated metabolites as instrumental variable exposures against a published HT genome-wide association study.

Key Findings:

• HT prevalence was 29.3% (2,305/7,878).
• Female sex (OR 1.97, 95% CI 1.68 to 2.33), elevated total cholesterol (OR 1.13, 95% CI 1.02 to 1.26), and lower fasting glucose (OR 0.95, 95% CI 0.91 to 1.00) were independent metabolic predictors of HT.
• Adequate tuber intake (50–100 g/day) was protective against HT (OR 0.75, 95% CI 0.64 to 0.88).
• Excessive tuber intake (>100 g/day) was associated with increased HT risk (OR 1.50, 95% CI not provided).
• Genetically predicted folic acid supplementation increased HT risk across all MR methods (IVW: β = 0.105, SE = 0.001; P < 0.001).

Interpretation:

Adequate tuber intake is associated with a lower likelihood of HT, while high-dose folic acid supplementation is linked to increased risk.

Limitations:

• Observational nature of the study may introduce confounding.
• Cross-sectional design limits causal inference.

Conclusion:

Moderate tuber consumption may be associated with lower HT risk, while high-dose folic acid supplementation is linked to increased risk.