Beneficial role for folate in the prevention of colorectal and breast cancer

Folate is involved in the synthesis of nucleotides and amino acid metabolis m such as methylation of homocysteine to methionine. Methionine is activate d by adenosine triphosphate (ATP) to produce S-adenosylme-thionine (SAM), t he primary intracellular methyl donor. Thus, folate is essential for the sy nthesis, methylation, and repair of DNA. With regard to its biochemical fun ction it has been hypothesized that a diminished folate status may contribu te to carcinogenesis by alteration of gene expression and increased DNA dam age. Animal and human studies support this hypothesis, particularly with re spect to colorectal cancer. Epidemiological evidence for the association be tween folate status and cancer was first observed among ulcerative colitis patients. Several case-control studies demonstrated reduction in colorectal cancer risk with better folate status. Two large, prospective cohort studi es support the concept that high folate intake is protective against colon cancer. In contrast to colorectal cancer, the potential association of fola te status and risk has been less investigated in breast cancer. Recently, c onvincing epidemiological data establishing a positive effect of folate sta tus on breast cancer risk were published. This review summarizes the epidemiological evidence for the association bet ween folate status and colorectal and breast cancer risk. In addition, a sh ort overview is given on the discussed mechanism(s) by which folate might b e involved in carcinogenesis.