A large U.S. study finds that heavy drinking across adulthood significantly raises the risk of colorectal and rectal cancer, while people who quit may see their risk drop back toward light drinkers. The findings add new urgency to conversations about alcohol, cancer and prevention.
How much you drink over the course of your life may matter more for colon health than the occasional big night out, new research suggests.
A long-term study of more than 88,000 U.S. adults has found that people who averaged at least 14 alcoholic drinks a week across adulthood faced a substantially higher risk of colorectal cancer — and an especially high risk of rectal cancer — than those who drank very little. The study also offers a hopeful message: people who quit drinking did not show the same elevated risk.
The findings, published online in the American Cancer Society journal Cancer, deepen evidence that alcohol is not just a short-term health concern but a long-term cancer risk factor that can build over decades.
Researchers analyzed data from the National Cancer Institute’s Prostate, Lung, Colorectal, and Ovarian (PLCO) Cancer Screening Trial, which followed participants who did not have cancer at the start of the study. Over 20 years of follow-up, 1,679 cases of colorectal cancer were diagnosed among 88,092 participants.
When the team looked at average lifetime alcohol intake, they found a clear pattern. Current drinkers who averaged 14 or more drinks per week — a level the researchers classified as heavy drinking — had a 25% higher risk of developing colorectal cancer than people who averaged less than one drink per week. For rectal cancer specifically, the risk was 95% higher among these heavy drinkers compared with very light drinkers.
The picture became even sharper when the researchers examined how consistently people drank over their adult lives. Those who reported heavy drinking throughout adulthood had a 91% higher risk of colorectal cancer than people who consistently drank very lightly.
The study also looked at noncancerous growths called adenomas, which can develop into colorectal cancer over time. Understanding who is more likely to develop adenomas can help doctors target screening and prevention efforts earlier.
In contrast to the increased risks seen among heavy current drinkers, the researchers did not find evidence of higher colorectal cancer risk among former drinkers. Former drinkers also had lower odds of developing adenomas than current drinkers who averaged less than one drink per week. That pattern suggests that stopping drinking may help lower a person’s risk, although the authors cautioned that the data on former drinkers were limited.
Co-senior author Erikka Loftfield, a researcher at the National Cancer Institute, noted the work fills an important gap in understanding how alcohol affects cancer risk over time.
“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,” Loftfield said in a news release.
Colorectal cancer is one of the most commonly diagnosed cancers worldwide and a leading cause of cancer deaths. While age and family history are major risk factors, lifestyle choices — including diet, physical activity, smoking and alcohol use — also play a significant role.
Previous research has linked alcohol to colorectal cancer, but many studies have focused on drinking at a single point in time or over relatively short periods. By looking at alcohol intake across adulthood and tracking both adenomas and cancer over two decades, the new study offers a more complete picture of how long-term drinking patterns relate to disease.
Scientists are still working to understand exactly how alcohol promotes cancer. One leading idea is that when the body breaks down alcohol, it produces a compound called acetaldehyde, which can damage DNA and interfere with cells’ ability to repair that damage. Alcohol may also affect hormones and promote inflammation, and it can alter the community of microbes in the gut, which in turn may influence cancer risk.
The authors noted that more research is needed to test these biological mechanisms and to better understand how risk changes after people reduce or stop drinking. Because the data on former drinkers were sparse, the apparent return to lower risk needs to be confirmed in other large studies.
For now, the findings add weight to public health recommendations that encourage people to limit alcohol to reduce cancer risk. Many guidelines already advise that if adults choose to drink, they should do so in moderation — and that not drinking at all is the option that carries the lowest risk.
For individuals, the results underscore that alcohol is not just about liver health or short-term effects like hangovers. It is a factor that can shape cancer risk over many years.
The hopeful signal around former drinkers also suggests that it may never be too late to reconsider drinking habits. While no single study can offer guarantees, the new research indicates that cutting back or quitting alcohol could be one meaningful step toward protecting colon health over the long term.
Source: Wiley