Alcohol and cancer: why the risk goes far beyond the liver

When we talk about the effects of alcohol on health, one association tends to come to mind almost automatically: alcohol and the liver. Cirrhosis, fatty liver disease and alcoholic hepatitis are some of the consequences we already know about. However, there is another link that has been supported by scientific evidence for decades but still seems far less widely understood: alcohol consumption also increases the risk of developing several types of cancer.

The International Agency for Research on Cancer (IARC) has classified alcoholic beverages as carcinogenic to humans since 1987, so this is not a recent warning. There is currently sufficient causal evidence to link alcohol consumption to at least seven cancer sites.

A recent analysis published in The Lancet Regional Health – Americas has once again brought this relationship into focus. According to its findings, the estimated number of cancer deaths attributable to alcohol in the United States rose from 11,361 in 1990 to 23,126 in 2023. But perhaps what matters most is not simply that the figure has increased, but which types of cancer are behind these deaths and at what ages they occur.

It is not only about liver cancer

The analysis uses more than three decades of data from the Global Burden of Disease to examine how cancer mortality attributable to alcohol consumption has changed over time.

Cancers linked to alcohol include those affecting the colon and rectum, breast, oesophagus, mouth, pharynx and larynx.

Among adults aged 20 to 54, for example, colorectal cancer accounted for the highest alcohol-attributable mortality among men. In women of the same age group, breast cancer ranked first, followed by colorectal cancer.

How can alcohol contribute to different types of cancer?

When we drink alcohol, the body has to break it down so it can be eliminated. During this process, acetaldehyde is produced, a substance that can damage cellular DNA and interfere with some of its repair mechanisms.

If these alterations occur repeatedly over time, they can increase the likelihood of cellular changes associated with tumour development. However, this is not the only way in which alcohol can influence cancer risk.

Alcohol consumption can also promote oxidative stress, affect the way the body uses certain nutrients and alter hormone levels. The latter is particularly relevant in breast cancer, as alcohol can influence oestrogen levels.

These effects can also interact with other risk factors. When alcohol and tobacco are consumed together, for example, they can intensify tissue damage and particularly increase the risk of certain cancers of the mouth and throat.

What if alcohol consumption is low?

This is probably one of the most common questions. For years, the idea of “moderate” drinking has often been discussed as though there were a clear threshold beyond which alcohol becomes harmful. When it comes to cancer, however, that threshold is not so straightforward.

In general, risk increases as the amount of alcohol consumed rises, but it can also begin to increase at relatively low levels of consumption, particularly for certain cancers such as breast cancer. For this reason, the World Health Organization states that, from the perspective of cancer risk, no level of alcohol consumption can be considered completely risk-free.

This does not mean that having one drink will cause cancer, nor that two people with the same drinking pattern will necessarily develop the same disease.

We are talking about probabilities, not certainties that apply equally to everyone.

Many other factors influence a person’s overall risk, including age, genetic predisposition, smoking, diet, physical activity, environmental exposures and biological factors that we still cannot fully control or predict.

What the available evidence does allow us to say is something simpler: the lower the exposure to alcohol, the lower the risk that can be attributed to it.

What does it really mean when a death is “attributable to alcohol”?

It is worth stopping to understand this expression in order to interpret the study’s figures correctly.

The 23,126 deaths recorded for 2023 do not correspond to death certificates stating that alcohol was the direct cause of death. They are epidemiological estimates calculated by combining data on alcohol consumption, known cancer risks, population figures and mortality.

These tools make it possible to estimate what proportion of disease may be statistically associated with a particular risk factor.

It would therefore also be incorrect to conclude that an individual’s risk of dying from an alcohol-related cancer has doubled since 1990 simply because the absolute number of estimated deaths has increased. Over more than three decades, the size and age structure of the US population, drinking patterns, the incidence of different cancers and many other factors have also changed.

A link well known to science, but not always to the public

It is particularly striking to compare the way society perceives alcohol with the way it perceives tobacco.

Today, it is difficult to find someone who does not know that smoking increases the risk of cancer. With alcohol, that relationship is not always perceived as clearly, partly because drinking is deeply embedded in many social and cultural settings.

The IARC classification helps show how firmly established the evidence is: alcohol belongs to Group 1 of agents carcinogenic to humans, the category used when there is sufficient evidence that an exposure can cause cancer. Tobacco smoke and asbestos are also included in this group.

This does not mean that drinking alcohol, smoking or being exposed to asbestos involve exactly the same level of risk. The classification reflects the strength of the evidence that an agent can cause cancer, not how great the risk is or how much exposure is required for it to occur.

And that is precisely where an important part of health education comes in: knowing about a risk factor does not turn a behaviour into a certainty of disease, but it does make it possible to assess its possible consequences more accurately and make decisions with more complete information.

In the case of alcohol, that information also includes a link with cancer that is still not always perceived as clearly as other effects associated with its consumption.