Brazil study links drinking pattern to 91% higher colon cancer risk

A long-term study found that people who were consistent heavy drinkers throughout their adult lives had a 91% higher risk of developing colorectal cancer compared to light drinkers. The research tracked alcohol intake from early adulthood through midlife and beyond, using data from the Prostate, Lung, Colorectal, and Ovarian Cancer Screening Trial, a large U.S. study that followed participants for up to two decades.

Participants reported their alcohol consumption across four life stages, starting at age 18. Researchers calculated average lifetime alcohol intake in drinks per week and categorized participants by drinking patterns, including consistent light, moderate, or heavy drinking, as well as former drinking status. The study tracked two key outcomes: colorectal cancer and colorectal adenomas, which are benign growths that can develop into cancer over time.

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 consumed less than one drink per week. For rectal cancer specifically, the risk jumped to 95% higher for heavy lifetime drinkers. The most striking finding involved people who were consistent heavy drinkers throughout their lives, maintaining that pattern over time. These individuals faced a 91% higher risk of colorectal cancer compared to consistent light drinkers.

Moderate drinkers who averaged seven to less than 14 drinks per week had a 21% lower risk of colorectal cancer compared to the lightest drinkers, particularly for distal colon cancer, which is the part of the colon closer to the rectum. The researchers noted that this does not mean moderate drinking is protective. It likely reflects something about the comparison groups or other lifestyle factors that the study could not fully account for.

Stopping drinking may lower risk

Former drinkers had a 42% lower risk of developing non-advanced adenomas compared to current light drinkers. Since adenomas are the precursors to most colorectal cancers, this suggests that quitting drinking could interrupt the cancer development process. The findings indicate that the body appears to have some capacity to recover from previous alcohol exposure when a person stops drinking.

The biological mechanisms behind alcohol’s cancer-promoting effects are well understood. When a person drinks, the body breaks down alcohol into acetaldehyde, a compound classified as a carcinogen. This substance directly 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 and uses folate, a B vitamin crucial for healthy DNA function. When folate metabolism gets disrupted, it can lead to abnormal DNA methylation patterns, which are often among the first steps toward cancer development.

Alcohol also affects the gut microbiome, potentially disrupting the balance of bacteria that influence immune function, inflammation levels, and cell growth in the intestinal lining. Chronic low-grade inflammation creates a fertile environment for abnormal cells to grow and persist, especially when exposure continues for decades.

Colorectal cancer is showing up in younger adults at alarming rates. The research reinforces that colorectal cancer risk is shaped by long-term patterns, not isolated behaviors. Regularly exceeding 14 drinks per week over many years was consistently 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 a higher risk in this study, alcohol remains a known carcinogen, and benefits may reflect confounding lifestyle factors rather than alcohol itself.

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. Fiber intake, physical activity, body composition, and limiting processed meats also play significant roles in colorectal cancer prevention.