The relationship between iodine intake and the risk of thyroid cancer: A meta-analysis

Thyroid cancer (TC) is the most common malignancy of the endocrine system. The relationship between iodine intake and TC risk is controversial always. We aim to figure out the relationship between iodine intake and TC using meta-analysis. Literature research in MEDLINE, Embase, China National Knowledge Infrastructure, and China BioMedicine was performed up to April 2016, searched for relevant case-control and cohort studies. The effect of iodine consumption on the risk of TC was assessed using the pooled odds ratio (OR) and 95% confidence interval (CI). The meta-analysis included 8 case-control studies (n = 4974; 2213 cases; 2761 controls). More than adequate or excess iodine intake (>300 μg/d) decreased the risk of TC (OR 0.74, 95% CI 0.60, 0.92). High consumption of saltwater fish or shellfish decreased the risk of TC (OR 0.72, 95% CI 0.55, 0.95; OR 0.70, 95% CI 0.52, 0.96; respectively). A higher intake of dietary iodine was as a protective factor for TC. However, the available data are very limited and more studies are required.