Obesity may modify the association between alcohol consumption and the risk of colorectal cancer

A case-control study from Newfoundland/Labrador has reported that greater alcohol intake may increase the risk of colorectal cancer (CRC) among obese subjects, but not among non-obese subjects. This is not a particularly large study, and only 45-60% of subjects who were recruited by telephone ended up providing data. Further, it is a case-control comparison, rather than a cohort analysis, making bias in the results more likely.

In this study, there was no relation of alcohol with the risk of CRC when considering the entire population. However, when subjects were stratified by BMI (<30 versus = 30), the data indicate an increase in CRC risk for obese subjects who were "drinkers" (OR=2.2, 95% CI 1.2-4.0), especially among subjects reporting 5 or more drinks/daily (OR=3.7, CI 1.5-9.0). On the other hand, even among obese subjects there was not a clear dose-response effect noted, i.e., there was not a step-wise increase in CRC risk with greater number of drinks/day. For example, the odds ratio (OR) was 2.3 times that of non-drinkers for obese subjects reporting 1-2 drinks/daily and 1.3 for those reporting 3-4 drinks/daily.

It will be interesting to determine if other studies show that there is modification of the association between alcohol intake and colorectal cancer by obesity. If such is the case, it could help understand some of the mechanisms for the development of cancer and provide better guidelines for screening for CRC.