Coffee and tea both contain compounds that could potentially help prevent colorectal cancer, but findings from previous studies on the relationship between coffee and tea consumption and colorectal cancer risk have been mixed.

It could be that coffee and tea consumption have different effects on different sites in the gut. Epidemiological studies suggest that the risk factors for cancer in the proximal colon, distal colon, and rectum may differ.

For this study, researchers used data from the NIH-AARP Diet and Health study to see how coffee and tea consumption affect the risk of cancer at these three sites. Study participants included 489,706 older adults who were tracked for an average of 10.5 years. During follow-up 2,863 cases of proximal colon cancer, 1,993 cases of distal colon cancer, and 1,874 cased of rectal cancer were identified.

Tea consumption was not associated with the risk of colon or rectal cancer. Higher consumption of caffeinated coffee was associated with a decreased risk of colon cancer, while higher consumption of decaffeinated coffee was associated with lower risk of colon and rectal cancer.

The beneficial effect of coffee consumption was strongest for cancers in the proximal colon, with no significant associations to cancers in the distal colon. Limitations of this study include self-reported tea and coffee consumption and the possibility that the lifestyle of people who drank decaffeinated coffee was different from those who drank caffeinated coffee. If so, that could have affected the findings.