Folic acid, a crucial vitamin B9, plays a significant role in various biological processes, including cell maturation and proliferation. This review examines the conflicting data regarding folic acid's role in cancer development and progression. While some studies suggest that folic acid can reduce the risk of certain cancers, others indicate potential carcinogenic effects. The review highlights molecular mechanisms that explain these contrasting findings, such as DNA synthesis, DNA methylation, homocysteine regulation, and antioxidant properties. Additionally, it discusses the protective mechanisms of folic acid, including its role in DNA synthesis, gene expression, and DNA repair. However, high-dose folic acid supplementation may have adverse effects, particularly in individuals with pre-existing cancer or precancerous lesions. The review also explores the mandatory fortification of folic acid in food, its public health impact, and the potential carcinogenic effects of excessive intake. Future research is needed to provide a comprehensive understanding of folic acid's role in cancer, including pharmacogenomic studies and multicenter clinical trials.Folic acid, a crucial vitamin B9, plays a significant role in various biological processes, including cell maturation and proliferation. This review examines the conflicting data regarding folic acid's role in cancer development and progression. While some studies suggest that folic acid can reduce the risk of certain cancers, others indicate potential carcinogenic effects. The review highlights molecular mechanisms that explain these contrasting findings, such as DNA synthesis, DNA methylation, homocysteine regulation, and antioxidant properties. Additionally, it discusses the protective mechanisms of folic acid, including its role in DNA synthesis, gene expression, and DNA repair. However, high-dose folic acid supplementation may have adverse effects, particularly in individuals with pre-existing cancer or precancerous lesions. The review also explores the mandatory fortification of folic acid in food, its public health impact, and the potential carcinogenic effects of excessive intake. Future research is needed to provide a comprehensive understanding of folic acid's role in cancer, including pharmacogenomic studies and multicenter clinical trials.