Consistent Heavy Alcohol Intake Increases the Risk of Colorectal Cancer

New research shows that drinking alcohol is associated with an elevated risk of developing colorectal cancer, with the risk especially pronounced for rectal cancer. The findings, published in Cancer, strengthen evidence that heavy and consistent alcohol use contributes to cancer development, while quitting drinking may reduce risk.

The study drew on data from 88,092 adults who participated in the National Cancer Institute’s Prostate, Lung, Colorectal, and Ovarian Cancer Screening Trial. None had cancer at enrollment, and they were followed for 20 years. During that period, 1,679 participants developed colorectal cancer. Researchers evaluated the effects of both lifetime alcohol intake and consistent drinking patterns over adulthood.

Current heavy drinkers—those averaging at least 14 drinks per week—had a 25% higher risk of developing colorectal cancer compared with those averaging less than one drink per week. The elevated risk was especially evident for rectal cancer, where heavy drinkers faced a 95% higher risk than light drinkers. When drinking patterns were examined over time, individuals who consistently drank heavily throughout adulthood had a 91% higher risk of colorectal cancer compared with consistent light drinkers.

No increased risk was observed among former drinkers. In fact, former drinkers had lower odds of developing adenomas—noncancerous colorectal growths that can progress to cancer—than current light drinkers. Although data on this group were limited, these results suggest that stopping drinking may help lower a person’s long-term cancer risk.

Researchers suggested several biological explanations for the link between alcohol and colorectal cancer. These include carcinogenic substances produced during alcohol metabolism and possible disruptions to gut microbes. Additional research will be necessary to confirm how these factors contribute to cancer formation.

“Our study is one of the first to explore how drinking alcohol over the life course relates to both colorectal adenoma and colorectal cancer risk. While the data on former drinkers were sparse, we were encouraged to see that their risk may return to that of the light drinkers,” said co–senior author Erikka Loftfield of the National Cancer Institute, part of the National Institutes of Health.