Dietary Pattern and Risk of Thyroid Cancer: A Systematic Review.

The incidence of thyroid cancer (TC) has significantly increased over the past decades due to a few recognised risk factors. Although the relationship between dietary factors and TC is still not fully understood, emerging evidence suggests that certain dietary habits may influence the risk of developing this type of cancer. This systematic review (PROSPERO ID: CRD42023463802) investigated the association between dietary patterns and TC risk using the available evidence. Five databases were searched (PubMed/Medline, Embase, Scopus, Web of Science and LILACS) for observational studies in adults comparing unhealthy and healthy dietary patterns among individuals diagnosed with TC-between September 2023 and January 2025, without restrictions on language or publication year. Three independent reviewers conducted study selection and data extraction. Forty-five studies were included (two cross-sectional, thirteen cohort and thirty case-control). A posteriori patterns rich in vegetables, fruits, fish, lean meat, dairy products and unsaturated fats were significantly associated with reduced TC risk, whereas starchy foods, seafood, seaweed, processed meats, instant foods, fast food and Western patterns increased risk. A priori patterns with higher inflammatory potential were also positively associated with TC risk. Most studies demonstrated good methodological quality, according to NOS assessment. This systematic review suggests that dietary patterns may be associated with TC risk. Although healthier dietary patterns tended to be associated with a lower risk and pro-inflammatory or Western-style dietary patterns with a higher risk, the current evidence remains observational and heterogeneous. Further prospective studies are needed to clarify the biological mechanisms underlying these associations.