Dairy product consumption and thyroid cancer risk: a systematic review and meta-analysis of observational studies

The relationship between regular dairy consumption and thyroid cancer (TC) risk remains inconclusive. This study aims to clarify this association through a systematic review and meta-analysis.

We systematically searched PubMed, EMBASE, and Web of Science for observational studies published until September 1, 2025. Following PICOS (participants, interventions, comparisons, outcomes, and study design) criteria, eight articles were included from 298 initially identified records.

Eight studies were included in the meta-analysis. The overall pooled analysis found no significant association between dairy consumption and TC risk [odds ratio (OR): 0.92, 95% confidence interval (CI): 0.72-1.17], with considerable heterogeneity (I²=67.9%, P=0.003). Subgroup analyses by study design (cohort OR: 0.85; case-control OR: 1.04), geography, and study quality showed no significant associations or subgroup differences. Adjustments for total energy intake or age did not materially alter the results. Studies adjusting for total energy intake yielded an OR of 0.89, compared to an OR of 0.94 in studies without such adjustment. Notably, age adjustment was identified as a key source of heterogeneity, reducing it to I²=0.0%. Sensitivity analyses confirmed the robustness of the findings, with no single study substantially influencing the overall results. The funnel plot indicated possible publication bias; however, Begg's and Egger's tests did not support significant publication bias statistically.

This meta-analysis demonstrates no significant association between dairy consumption and TC risk. The findings were consistent across subgroups and robust in sensitivity analyses. Further large-scale, high-quality prospective studies are needed to confirm these findings and explore potential underlying mechanisms.