While heavy alcohol consumption is recognized as a contributor to the development of colorectal cancer (CRC), an increasing number of studies suggest that moderate alcohol consumption may not have an adverse effect on the risk of CRC, or even decrease the risk.
The present paper, a meta-analysis of 16 studies on the relation of alcohol consumption to invasive CRC, was conducted by leading investigators in the field. Forum members consider this to be a well-done study, with a large number of subjects, the ability to use individual level data in their meta-analysis, and the use of appropriate and complete analytic techniques.
The key finding of their study was that there was a J-shaped curve evident in all of their analytic approaches; their results strongly support a J-shaped association for the relation of alcohol intake to CRC: a slightly lower risk of cancer for light to moderate drinkers and an increased risk for subjects reporting an average of 3 or more drinks/day. Further, they found that their results did not vary by age, obesity, smoking, or family history of CRC. Overall, the effects of benefits/harms were somewhat more striking for cancers in the distal colon than in the proximal colon.
Potential mechanisms for heavy alcohol consumption being related to an increase in risk were discussed by the authors. As for moderate drinking decreasing the risk, potential mechanisms are discussed by a Forum member in this critique. He describes active, beverage-specific metabolites other than ethanol that reach the intestine. In particular, our attention goes to the several microbial catabolites which can be formed via our host microbiota in the colon.
The finding of a J-shaped curve between alcohol and CRC is similar to the relation seen for a number of other diseases, including coronary artery disease, ischemic stroke, dementia, and total mortality. While a linear relation between heavy drinking and certain upper aero-digestive tract cancers has been shown, for certain cancers there may be a J-shaped curve of effect, with reductions in risk for light-to-moderate drinkers.
Reference: McNabb S, Harrison TA, Albanes, Berndt S, Brenner H, Caan BJ, et al. Meta-analysis of 16 studies of the association of alcohol with colorectal cancer. Int J Cancer. 2019 Apr 29. doi: 10.1002/ijc.32377.