For many people, having a glass of wine with dinner or sharing drinks with friends is a normal part of life.
Moderate alcohol use is often viewed as harmless and is closely tied to celebrations, social events, and relaxation.
However, scientists have been uncovering a less visible side of alcohol use for many years. Growing evidence shows that drinking alcohol can increase the risk of several serious health problems, including liver disease, heart conditions, and certain types of cancer.
One cancer that has attracted increasing attention is colorectal cancer, which affects the colon and rectum. Colorectal cancer is one of the most common cancers worldwide and is a major cause of cancer-related deaths. The disease often begins with small growths called adenomas or polyps inside the colon or rectum.
These growths are usually not cancerous at first, but some can slowly develop into cancer over many years. Age, family history, smoking, obesity, lack of physical activity, and diet are all known risk factors. Scientists now believe that long-term alcohol use should also be considered an important and preventable risk factor.
A large new study suggests that the amount of alcohol a person drinks throughout life may matter even more than how much they are drinking right now. The research found that people who consumed larger amounts of alcohol over their lifetime had a significantly higher risk of developing colorectal cancer.
The study was published in the journal CANCER, a peer-reviewed publication of the American Cancer Society.
Researchers analyzed data from the National Cancer Institute’s Prostate, Lung, Colorectal, and Ovarian Cancer Screening Trial, a large long-term study involving adults from across the United States. All participants were free of cancer when the research began.
The scientists followed 88,092 participants for nearly 20 years. During this period, 1,679 people developed colorectal cancer. Because the study lasted for such a long time, the researchers were able to examine how drinking habits across many decades influenced cancer risk later in life.
Unlike many earlier studies that focused only on current drinking habits, the researchers carefully examined lifetime alcohol intake. They classified people who averaged 14 or more alcoholic drinks per week over their lifetime as heavy drinkers. They then compared these individuals with people who averaged fewer than one alcoholic drink each week throughout their lives.
The findings revealed a clear pattern. Heavy lifetime drinkers had a 25 percent higher risk of developing colorectal cancer than lifelong light drinkers. The link was even stronger for rectal cancer, which affects the last section of the large intestine. Heavy drinkers had nearly double the risk of developing rectal cancer compared with those who drank very little.
The researchers also looked at drinking patterns over adulthood. People who drank heavily for many years had a much greater risk than people who consistently consumed only small amounts of alcohol.
Long-term heavy drinkers had a 91 percent higher risk of colorectal cancer than lifelong light drinkers. These results suggest that the effects of alcohol may slowly accumulate over time, gradually increasing the likelihood that cancer will develop.
Scientists are still trying to understand exactly why alcohol raises the risk of colorectal cancer. One possible explanation involves a substance called acetaldehyde, which is produced when the body breaks down alcohol. Acetaldehyde is toxic and can damage DNA, making it harder for cells to repair themselves properly.
This damage may increase the chances that normal cells become cancerous. Researchers also suspect that alcohol can disturb the balance of bacteria living in the gut. These changes may promote inflammation and create conditions that encourage tumor growth.
One of the most encouraging findings involved people who had stopped drinking alcohol. Former drinkers did not have a higher risk of colorectal cancer than people who drank very little throughout their lives.
They also appeared less likely to develop colorectal adenomas, the noncancerous growths that can sometimes turn into cancer. Although the number of former drinkers in the study was relatively small, the findings suggest that quitting alcohol may help reduce risk over time.
The study adds to growing evidence that long-term alcohol exposure can quietly affect health in ways that may not become obvious for many years. The especially strong connection between alcohol and rectal cancer also suggests that different parts of the digestive system may respond differently to alcohol-related damage.
Overall, the findings provide another reminder that lifestyle choices made over decades can have important effects on future health. While moderate drinking may appear harmless in the short term, regular heavy drinking over many years may significantly increase the risk of colorectal cancer.
For people concerned about protecting their long-term health, reducing alcohol intake or stopping drinking altogether may be a meaningful step toward lowering the risk of this common and potentially life-threatening disease.
If you care about cancer, please read studies that a low-carb diet could increase overall cancer risk, and berry that can prevent cancer, diabetes, and obesity.
For more health information, please see recent studies about how drinking milk affects the risks of heart disease and cancer and results showing vitamin D supplements could strongly reduce cancer death.
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