The Dual Effect of Folic Acid Supplementation in Preventing Colorectal Carcinomas

Abstract

Folic acid, a water-soluble B vitamin contained in vegetables, is essential for maintaining DNA stability through donating one-carbon-unit for cellular metabolism. So it plays an important role in DNA synthesis and replication. Early research suggested that folic acid could reduce the risk of colorectal cancer, but recent studies have questioned about this. Folic acid plays dual roles in the chemoprevention of colorectal cancer. Both the hopes for rapid cancer prevention and the fears about rapidly increased cancer risk from folic acid supplementation were not confirmed by folic acid supplementation. Folate deficiency may induce both gene-specific DNA hypermethylation and global DNA hypomethylation by its DNA-damaging effect. Meanwhile, the effect of folic acid in the development of colorectal cancer has a time-and dose-dependent pattern. Therefore, folate concentrations determined in duodenum or sigmoid colon epithelia are recommended so that a rational regimen could be made individually. We discussed the relationships between the effects of folic acid supplementation and colorectal cancer chemoprevention in the present review. The pros and cons of folic acid supplementation in tumor chemoprevention are still vague and need more efforts in the future.