How much alcohol people drink over the course of their lives, not just whether they drink now, may influence their risk of developing colorectal cancer, according to new research based on a large U.S. cancer screening trial.
The study, published in Cancer, analyzed data from nearly 90,000 adults enrolled in the Prostate, Lung, Colorectal, and Ovarian Cancer Screening Trial who were cancer-free at baseline. Over approximately 20 years of follow-up, researchers documented 1,679 cases of colorectal cancer.
Participants with an average lifetime alcohol intake of at least 14 drinks per week were found to have a 25% higher risk of colorectal cancer compared with people who averaged fewer than one drink per week. The association was stronger for rectal cancer, with heavy drinkers showing a 95% higher risk than light drinkers.
Patterns of drinking over time also appeared to matter. Individuals who drank heavily and consistently throughout adulthood had a 91% higher risk of colorectal cancer compared with those who consistently drank lightly. In contrast, researchers did not observe an increased risk among former drinkers, and former drinkers had lower odds of developing colorectal adenomas, noncancerous growths that can precede cancer, than current very light drinkers, though data for this group were limited.
“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,” said Erikka Loftfield, a senior author of the study and a researcher at the National Cancer Institute. “While the data on former drinkers were sparse, we were encouraged to see that their risk may return to that of the light drinkers.”
Researchers emphasized that the findings do not establish cause and effect. The analysis was observational, meaning it cannot rule out unmeasured factors that may influence both drinking behavior and cancer risk. Alcohol intake was self-reported, which can introduce recall error, particularly when estimating consumption across decades.
The study also did not directly test biological mechanisms. However, the authors noted that alcohol metabolism can produce carcinogenic compounds and that alcohol may influence gut microbes in ways that affect cancer risk, possibilities that warrant further investigation.
Taken together, the findings add to a growing body of evidence suggesting that cancer risk related to alcohol is shaped by cumulative exposure over time, rather than short-term drinking patterns alone. The results also suggest that reducing or stopping alcohol intake may be associated with lower colorectal cancer risk, even later in adulthood, though more research is needed to confirm this relationship.
This research was supported in part by the Intramural Research Program of the National Institutes of Health. Contributions from NIH authors were made as part of their official duties as federal employees. Additional support was provided by the National Cancer Institute and the Maryland Department of Health’s Cigarette Restitution Fund Program.