Why does alcohol increase the risk of cancer from the first drink?

Our bodies pay a price for alcohol, whether consumed regularly or occasionally. This substance has harmful effects on health , affecting many organs, from the brain to the gastrointestinal system, including the lungs, muscles (including the heart), and the immune system. It is now known that alcohol causes cancer, among other things.

In the United States, alcohol is responsible for approximately 100,000 cases of cancer and 20,000 cancer deaths each year, making it the third leading preventable cause of cancer . For comparison, alcohol-related traffic accidents cause approximately 13,500 deaths annually in the United States.

( In France, in 2018, 28,000 new cases of cancer were attributable to alcohol, or 8% of incident cancer cases, with a distribution of 11% among men and 4.5% among women. Road accidents linked to alcohol and/or drug consumption caused nearly 1,250 deaths in 2024 , with alcohol being involved in three-quarters of cases, editor's note).

Scientists have suspected that alcohol can cause cancer since the 1980s . Epidemiological studies have since shown that alcohol consumption increases the risk of cancers of the oral cavity, throat, larynx, esophagus, liver, colon and rectum, and breast . Other studies have revealed an association between chronic drinking or occasional heavy drinking and pancreatic cancer .

In 2000, officials from the U.S. National Toxicology Program concluded that the consumption of alcoholic beverages should be considered a known human carcinogen . In 2012, the International Agency for Research on Cancer (IARC), the World Health Organization's cancer agency, classified alcohol as a Group 1 carcinogen . A substance's inclusion in this category, the highest in the IARC classification, indicates that there is sufficient scientific evidence to conclude that it causes cancer in humans. TheCenters for Disease Control and Prevention and the National Institutes of Health also agree that the evidence is conclusive: alcohol does cause various types of cancer.

Furthermore, in the United States ( as in France , editor's note), health authorities emphasize that even small quantities of alcohol – less than one glass per day – increase the risk of cancer .

Despite this, many citizens are unaware that alcohol causes cancer . In 2019, less than 50% of adults in the United States were aware of the links between alcohol consumption and cancer risk.

In France, the link between alcohol and cancer is also underestimated by a portion of the population. The 2021 Cancer Barometer survey, conducted by the National Cancer Institute, revealed that 38.6% of respondents believe that "it is mainly hard liquor that increases the risk of cancer," while 23.5% believe that "overall, drinking a little wine reduces the risk of cancer rather than not drinking any at all," even though the " French paradox" _is now being debunked, Editor's note_.

Additionally, the 2023 edition of the National Survey on Drug Use and Health found that more than 224 million Americans , aged 12 and older, had consumed alcohol at some point in their lives—more than 79% of people in this age group. Alcohol consumption was already increasing before the Covid-19 pandemic , which is a public health concern.

In France, according to data collected by Public Health France, daily alcohol consumption has been steadily decreasing for thirty years. However, it is noted that, while "heavy occasional drinking" tends to decrease among young men, it is increasing significantly among women over 35. In both cases, regional disparities are marked, Editor's note.

As a researcher, I study the biological effects of moderate and long-term alcohol consumption . My team is working to elucidate the mechanisms by which alcohol increases the risk of cancer, particularly through damage to immune cells and the liver.

Cancer occurs when cells begin to grow uncontrollably in the body. Alcohol can promote tumor formation by damaging DNA , causing mutations that disrupt cell division and growth.

Researchers have identified several mechanisms that may explain how alcohol consumption leads to the development of cancer. A 2025 report by the U.S. Surgeon General listed four main pathways by which alcohol can cause cancer:

The term "alcohol metabolism"—the primary pathway by which this substance can cause cancer—refers to the processes by which the body breaks down and eliminates alcohol. Once ingested, it undergoes chemical transformations by various enzymes that allow it to be eliminated (it is said to be "metabolized"). The first by-product of these reactions is acetaldehyde, a substance itself classified as a carcinogen . Scientists have shown that certain genetic mutations can cause some individuals' bodies to break down alcohol more quickly , leading to increased levels of acetaldehyde.

The second way in which alcohol increases the risk of cancer involves other harmful molecules called free radicals . Alcohol can trigger the release of these chemically highly reactive molecules, which damage cellular DNA, proteins, and lipids through a process called oxidative stress. My lab has shown that free radicals from alcohol consumption can directly affect how cells synthesize and degrade proteins , leading to the production of abnormal proteins that fuel inflammation that promotes tumor formation.

Cancer risk may also be increased by alcohol in a third way, due to its ability to alter hormone levels. It is known that moderate alcohol consumption can not only increase estrogen levels, but also encourage continued drinking . However, research has shown that breast cancer risk can be increased by estrogen levels . Alcohol also increases breast cancer risk by reducing levels of vitamin A , which regulates estrogen.

Finally, alcohol increases the risk of cancer by interacting with other carcinogens. For example, it is known that people who drink and smoke have an increased risk of developing cancer of the mouth, pharynx, and larynx . This is because alcohol makes it easier for the body to absorb the carcinogens contained in cigarettes and e-cigarettes.

Based on current knowledge, the risk of cancer associated with long-term use of e-cigarettes appears to be much lower than that of tobacco cigarettes, but it is not zero (compared to not using them); the reason is the presence of certain potentially mutagenic or carcinogenic constituents in the aerosols generated by e-cigarettes, which could influence the risk of certain cancers, particularly in the case of prolonged use . However, additional data still needs to be collected to assess this risk, Editor's note.

Additionally, smoking alone can also cause inflammation, inducing free radicals that damage DNA.

If you drink alcohol, you may have wondered if there is a minimum safe dose. The answer from clinicians and scientists may not please you: Alcohol consumption is never safe.

The risk of cancer increases from the first drink and increases with the quantity consumed , regardless of the type of alcoholic beverage consumed.

In the United States, the Centers for Disease Control and Prevention , the National Institute on Alcohol Abuse and Alcoholism , and the U.S. Surgeon General recommend no more than one drink per day for women and two drinks for men.

In France, the guidelines for "low-risk" alcohol consumption do not distinguish between the sexes. To communicate on the subject, the authorities have adopted the formula: "[For your health, alcohol is a maximum of two glasses per day, and not every day (https://www.drogues.gouv.fr/campagne-alcool-nouveaux-reperes-de-consommation-moindre-risque)"], Editor's note.

Alcohol consumption is therefore a highly preventable cause of cancer.

However, there is currently no method for determining an individual's risk of developing alcohol-related cancer. Individual genetics, lifestyle, diet, and other factors can influence the propensity of alcohol to lead to tumor formation . One thing is certain: reconsidering your drinking habits can help protect your health and reduce your risk of cancer.

To go further

• The pages of the Alcool info service and Santé publique France websites devoted to the effects of alcohol on health;
• the NACRe network website page dedicated to the links between alcohol and cancer;
• the page of the Health Insurance website intended for the assessment of alcohol consumption.