No safe level of alcohol? Major study links even moderate drinking to higher cancer risk

For decades, the image of a glass of wine with dinner has been seen as moderate drinking, and at times, some have also called it healthy. But one of the most comprehensive reviews of alcohol and disease is adding to a growing body of evidence that, when it comes to alcohol, there is no safe limit. The conversation needs to change specifically with respect to cancer.

Published in Nature Health, the study found that alcohol consumption was associated with an increased risk of several cancers—including those of the breast, colon, liver, mouth, throat, oesophagus, pancreas and stomach. The risk generally increased with the amount of alcohol consumed, with cancers of the throat, larynx, and oral cavity showing some of the strongest associations.

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The study analysed data from 843 epidemiological studies involving millions of people worldwide. Researchers examined alcohol’s relationship with 20 major diseases, including ten cancers, cardiovascular diseases, liver disease, pancreatitis, diabetes and dementia.

The message, however, is unlikely to surprise oncologists.

“Alcohol is a known human carcinogen,” says Dr Sameer Kaul, senior oncologist, Indraprastha Apollo. “What this study suggests is that the association may extend to more cancers than we previously appreciated. But the evidence is still evolving,” he added.

The current study showed that even moderate alcohol consumption may increase the risk of nine cancers. This reinforces the well-established carcinogenic effects of alcohol.

“The evidence has been accumulating for years, but studies of this scale reinforce that alcohol is not just a liver issue—it is a cancer prevention issue. This study puts together all the evidence and builds a case for alcohol’s association with liver disease, cancers and other metabolic diseases,” says Dr Dodul Modal, Principal Director and Head of Radiooncology in Max Hospital Saket.

More than liver damage

Alcohol is converted into acetaldehyde, a toxic chemical that can damage DNA and interfere with the body’s ability to repair cells. Alcohol can also increase levels of hormones such as oestrogen, helping explain its association with breast cancer. In addition, it promotes chronic inflammation and may make it easier for other carcinogens, such as those in tobacco smoke, to penetrate tissues lining the mouth and throat.

“When alcohol is metabolised, it is converted into acetaldehyde, a toxic chemical that can damage cells and may cause mutations,” explains Dr Koul. “Alcohol can also damage the protective lining of the gastrointestinal tract, allowing harmful substances to interact more directly with cells.”

Over time, repeated cellular damage and impaired DNA repair can increase the likelihood that normal cells become cancerous.

The disease risks

Five health outcomes where alcohol increases the risk by 15–50%.

The strongest association, pharyngeal cancer, showed a 105% increased risk.

Nine outcomes increased the risk of developing a health condition by 0–15% or, in some cases, decreased the risk by 0–13%.

For five health diseases, the evidence was weak or inconsistent: stomach cancer, hemorrhagic stroke, ischemic stroke, tuberculosis, and ischemic heart disease.

Is there a safe limit?

One reason alcohol advice has often confused the public is that some earlier studies suggested light drinking might protect against heart disease.

The new analysis found that while low levels of alcohol were associated with slightly lower risks of a few cardiovascular conditions in some observational studies, these apparent benefits were uncertain and may reflect biases in the underlying research rather than alcohol itself.

For cancer, however, the pattern was much clearer. Risk rose steadily with increasing alcohol intake, and for some cancers, there was no obvious threshold below which risk disappeared entirely.

Experts say this doesn’t mean a single drink causes cancer, but exposure over the years damages the body. While other genetic, environmental, and lifestyle factors are important, every increase in alcohol exposure appears to increase the probability that harmful cellular changes will occur.

A public health challenge

Unlike tobacco, alcohol rarely features in cancer awareness campaigns. “Cigarette packets carry graphic warnings; alcohol bottles do not mention the risks at all. A person should be made aware of the risk, as happens with cigarettes. We all know both smoking and alcohol consumption increase the risk of the disease,’’ explains Dr Mondal.

Dr Mondal says that studies in several countries have found that many people are unaware that alcohol can cause cancer. Alcohol is called a Group 1 carcinogen along with tobacco smoke and asbestos.

No safe limit for alcohol?

The study is not a call for panic or prohibition. Instead, it reinforces that less alcohol means lower risks of diseases, including cancer.

Both doctors agree there is no safe limit for alcohol. “ Experts are now discussing redefining alcohol guidelines in many parts of the world,” says Dr Kaul.

So start by cutting down on the number of drinks you consume at social occasions. Never binge drink. Discuss with your doctor if there is a family history of cancer or a previous cancer diagnosis.

Cancer prevention has traditionally focused on smoking, obesity, physical inactivity, and infections. Alcohol experts say it deserves a place in that conversation.