Alcohol is a common part of social life for many people, and moderate drinking is often seen as harmless. However, scientific research has been steadily revealing a darker side of long-term alcohol use.
For years, studies have shown that drinking alcohol increases the risk of colorectal cancer, one of the most common cancers worldwide. Now, new research suggests that it is not just how much alcohol a person drinks now, but how much they drink over their entire lifetime, that plays a major role in shaping this risk.
The new findings come from a large study that followed tens of thousands of adults in the United States for nearly two decades. The research was published in the journal CANCER, a peer-reviewed publication of the American Cancer Society.
The results show a clear pattern: the more alcohol people consumed over their lifetime, the higher their chances of developing colorectal cancer. Among different types of colorectal cancer, rectal cancer appeared to be most strongly linked to heavy lifetime drinking.
To reach these conclusions, researchers analyzed health data from adults who took part in the National Cancer Institute’s Prostate, Lung, Colorectal, and Ovarian Cancer Screening Trial. All participants were cancer-free when the study began.
Over a follow-up period of about 20 years, 1,679 out of 88,092 participants were diagnosed with colorectal cancer. This long observation period allowed researchers to examine how long-term drinking habits affected cancer risk later in life.
The researchers paid close attention to lifetime alcohol intake rather than focusing only on recent drinking habits. They classified current drinkers who averaged 14 or more alcoholic drinks per week across their lifetime as heavy drinkers.
When compared with people who averaged fewer than one drink per week over their lifetime, heavy drinkers had a 25 percent higher risk of developing colorectal cancer. The link was even stronger for rectal cancer, where heavy drinkers faced nearly double the risk.
The study also examined how drinking patterns across adulthood influenced cancer risk. People who drank heavily for many years had a much greater risk than those who consistently drank small amounts. In fact, long-term heavy drinkers had a 91 percent higher risk of colorectal cancer compared with lifelong light drinkers.
These findings suggest that sustained exposure to alcohol over time may gradually damage the colon and rectum, increasing the chance that cancer will eventually develop.
One of the most encouraging findings involved people who had stopped drinking. Former drinkers did not show an increased risk of colorectal cancer compared with light drinkers.
They also had a lower chance of developing colorectal adenomas, which are noncancerous growths that can sometimes turn into cancer. Although the number of former drinkers in the study was relatively small, these results suggest that quitting alcohol may help lower cancer risk over time.
Scientists are still working to understand exactly how alcohol increases the risk of colorectal cancer. One possible explanation involves acetaldehyde, a toxic substance produced when the body breaks down alcohol.
Acetaldehyde can damage DNA and interfere with normal cell repair, increasing the chance of cancer. Alcohol may also disrupt the balance of bacteria in the gut, leading to inflammation and changes that promote tumor growth. More research is needed to confirm how these biological processes contribute to cancer development.
In reviewing and analyzing the study findings, the results strongly support the idea that long-term alcohol exposure matters. The study goes beyond earlier research by showing that lifetime drinking patterns, not just current alcohol use, are closely linked to colorectal cancer risk.
The especially strong association with rectal cancer highlights that different parts of the colon may respond differently to alcohol damage. Perhaps most importantly, the findings offer hope by suggesting that stopping alcohol use could reduce risk, bringing it closer to the level seen in people who drink very little.
Overall, this research adds to growing evidence that alcohol is a preventable risk factor for colorectal cancer. While moderate drinking may seem harmless in the short term, the cumulative effects over decades can quietly increase cancer risk.
For individuals concerned about colorectal cancer, reducing alcohol intake or quitting altogether may be a meaningful step toward protecting long-term health.
If you care about cancer, please read studies that a low-carb diet could increase overall cancer risk, and vitamin D supplements could strongly reduce cancer death.
For more information about health, please see recent studies about how drinking milk affects the risks of heart disease and cancer and results showing higher intake of dairy foods linked to higher prostate cancer risk.
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