Forest plot for the association between thyroid cancer risk and daily iodine intake. Effect on thyroid cancer reported as adjusted odds ratios (OR) for the highest iodine intake quantile compared to the lowest quantile. Studies are ordered ascending from lower to higher iodine intakes. Overall pooled OR 0.77 (95 % CI: 0.58, 1.02; p = 0.068). Between-study heterogeneity: I2 = 42.6 % (p = 0.058). Publication bias: Kendall’s Tau = 0.061 (p = 0.841). 1Sex: female (F), male (M); type of thyroid cancer: papillary (P), follicular (F), medullary (M). 2Low daily iodine intake. 3High daily iodine intake.