Folate intake and carcinogenesis of the colon and rectum.

Experimental evidence suggests that folate depletion plays a role in carcinogenesis. A case-control study examining folate intake was conducted. Some 428 colon and 372 rectal cancer cases with matched neighbourhood controls were interviewed regarding usual intake of foods, including food preparation. Unadjusted folate was not associated with risk of either cancer. Controlling for kilocalories, odds ratios (ORs) for those with the highest folate intake were 0.5 (95% confidence interval (CI): 0.24-1.03) and 0.31 (95% CI: 0.16-0.59) for females and males for rectal cancer. There was no change in colon cancer risk associated with folate intake. There was an indication of an interaction of folate and alcohol intake; the difference in risk associated with low and high folate intake was highest for males in the highest alcohol category. Associations were of similar magnitude for other dietary factors correlated with folate. It appears that intake of folate or a correlated factor may be negatively related to risk of rectal cancer.