MTHFR and cancer: However, in this study, we did not explore the effect of folate itself but rather the genetic susceptibility of the methylenetetrahydrofolate reductase (MTHFR) gene, which not only plays a crucial role in folate metabolism affected by alcohol consumption but also is involved in DNA synthesis, the methylation cycle, and epigenetic regulation18–21 and is a widely studied one-carbon metabolism-related gene with reported associations with all types of cancer, including thyroid cancer20,22–24.