A long-term study has found that people who consistently drink heavily throughout their adult life face a 91% higher risk of developing colorectal cancer compared to light drinkers.
The research used data from the Prostate, Lung, Colorectal, and Ovarian Cancer Screening Trial, a large U.S. study that followed participants for up to 20 years. Adults in the trial reported their alcohol consumption across four stages of life, starting at age 18. Researchers calculated average lifetime alcohol intake in drinks per week.
Participants were grouped into categories such as consistent light, moderate, or heavy drinkers, as well as former drinkers. The study tracked two outcomes: colorectal cancer and colorectal adenomas, which are benign growths that can turn into cancer. All participants were cancer-free at the start of the study.
Heavy lifetime drinkers, those averaging 14 or more drinks per week throughout their adult lives, had a 25% higher risk of colorectal cancer overall compared to the lightest drinkers, who had less than one drink per week. For rectal cancer specifically, the risk was 95% higher for heavy lifetime drinkers.
The most striking finding involved people who were consistent heavy drinkers throughout their lives. These individuals faced a 91% higher risk of colorectal cancer compared to consistent light drinkers. The study also found that moderate drinkers, those averaging seven to less than 14 drinks per week, had a 21% lower risk of colorectal cancer compared to the lightest drinkers. Researchers said this does not mean moderate drinking is protective, but may reflect other lifestyle factors the study could not fully account for.
Former drinkers had a 42% lower risk of developing non-advanced adenomas compared to current light drinkers. Since adenomas are precursors to most colorectal cancers, this suggests that quitting drinking may interrupt the cancer development process. The study could not prove that quitting caused the lower risk, but the timing and relationship strongly suggest that reducing alcohol offers protective benefits.
When the body breaks down alcohol, it produces acetaldehyde, a compound classified as a carcinogen. This substance damages DNA in colon and rectum cells and creates oxidative stress that can lead to cancer-promoting mutations. Acetaldehyde also interferes with how the body absorbs folate, a B vitamin important for healthy DNA function. Alcohol can disrupt the gut microbiome, which influences immune function, inflammation, and cell growth in the intestinal lining.
Colorectal cancer is appearing in younger adults at increasing rates. The research shows that risk is shaped by long-term patterns, not isolated behaviors. Regularly exceeding 14 drinks per week over many years was linked to higher colorectal cancer risk. Former drinkers showed lower odds of developing non-advanced adenomas, suggesting that risk reduction is possible. While moderate drinkers did not show higher risk in this study, alcohol remains a known carcinogen. The protective effects were strongest among participants who underwent regular colorectal screening, reinforcing the importance of colonoscopies starting at age 45, or earlier for those at higher risk.
