The link between alcohol and cancer

It is said that the discovery of alcoholic drinks goes as far back as Noah who enjoyed their virtues. One thing is certain: throughout history they have always accompanied meals, and especially celebrations, where alcohol is used to toast the occasion. But raising a glass can carry with it the risk of developing cancer, especially if the conventional recommendations are not followed, these were first issued by the International Agency for Research on Cancer (IARC), and then shared over the years by leading international organisations and scientific bodies. If you want to prevent cancer, it’s better not to drink.

Alcohol is a substance that affects our psychic functions and can therefore be addictive. It also causes various illnesses, serious traumas, accidents, as well as mental and behavioural disorders. This is partly why the World Health Organisation classifies it among the drugs capable of altering how the brain functions (as a psychoactive agent) and of causing addiction - to keep getting the same effects, the dose must be constantly increased. When describing drinks, the alcohol referred is ethanol, a substance created by the fermentation of certain simple sugars or by distilling fermented mash. More precisely, ethanol, or ethyl alcohol, is a molecule (CH3-CH2-OH) which is soluble in both water and lipids. It is very small, and this means it can easily penetrate tissues and enter the bloodstream, which is how it spreads through the body. All alcoholic drinks are mainly made up of ethanol and water; some nutrients (sugars, proteins, vitamins and minerals) can be present in alcoholic products but only in trace amounts, which is why they cannot be considered as a food even though these drinks are high in calories (7 kilocalories per gram). The body is not able to use ethanol for muscle work, but only for basic metabolism. This means that the body saves, so to speak, nutrients such as fats and sugars which are ingested in our diet, and these then contribute to weight gain by accumulating in the cells.

According to the World Health Organisation, Europe is the continent with the highest alcohol consumption of all. On average, considering all the various alcoholic drinks (beer, wine, cocktails, spirits, etc.), each European consumes around 9.24 litres per year. A habit that is not without consequences. The occurrence of alcohol-related diseases in Europe is double the global average. This figure shouldn’t come as a surprise, given that – in Europe – alcohol is considered the third biggest risk factor for death and disability after tobacco and hypertension, and the main threat to the health of young people as it increases the risk of road accidents. It is well known that alcohol affects the central nervous system, this can be observed in the acute effects of excessive drinking, and alcohol-related liver disease (ARLD) is another widely recognised consequence of alcohol consumption. But in actual fact, alcohol is also a type 1 human carcinogen. This means that it is one of the substances for which there is enough scientific evidence to prove it causes cancer, based on the IARC classification system. Specifically, alcohol is now considered a risk factor for cancer of the oral cavity (mouth), pharynx (throat), larynx (voice box), oesophagus (gullet), stomach, colorectum (large intestine and rectum), liver, gallbladder, and pancreas. This has also been confirmed by the findings of a large-scale study known as EPIC (The European Prospective Investigation into Cancer and Nutrition), which saw the participation of numerous researchers supported by the Italian AIRC Foundation for Cancer Research. The first data, which go back to 2011, demonstrate that 10 percent of all cancers affecting men and 3 percent of those affecting women can be attributed to drinking alcohol. Where Italy is concerned, estimates released in the Istisan reports issued by the Istituto Superiore di Sanità show that nearly 4 percent of cancer deaths are linked to drinking alcohol. This corresponds to almost twenty thousand lives that could have been saved by reducing alcohol consumption.

Breast cancer, the most common kind of cancer among women, is also sensitive to alcohol consumption. It’s a little-known risk factor for this disease, which was confirmed by the results of a study carried out in the UK and published in the journal BMJ Open in 2020, but for this very reason the link needs to be investigated. Drinking alcohol regularly can in fact be associated with between 5 and 11 percent of new breast cancer diagnoses (this means 2,500 to 5,000 new cases per year in Italy, for example). Almost all of these involve young women of childbearing age. There seem to be two reasons for this: firstly, the toxicity of alcohol is more acute. The second reason is that ethanol stimulates the action of oestrogen, and almost 70 percent of breast tumours grow in response to this hormone. These data worry the scientific community, because young people start drinking at an increasingly early age and are often involved in what’s called “binge drinking”. What is certain is that there is a direct relationship between the amount of alcohol consumed and the likelihood of developing breast cancer. The risk we are talking about is relative, i.e., an increased risk in those who drink compared to the baseline risk for the same disease in those who do not drink. The risk in drinkers compared to non-drinkers increases for each additional glass above the threshold of ten grams of ethanol per day (+7 percent). An increase that can almost quadruple (+27 percent) if the mammary gland tissue has oestrogen receptors.

Not all the ways in which alcohol contributes to the development of cancer are known yet. There are some things, however, that we do know for sure. For example, alcohol irritates the mucous membranes, preventing damaged cells from repairing themselves properly, this can favour the development of mouth and throat cancer. As alcohol is broken down by the liver – this organ has the task of making the substances that pass through it less toxic – it can cause changes and inflammation in liver cells, which may in time become cancerous. In the intestine, alcohol has at least two different effects: one is that alcohol is converted into acetaldehyde, a substance which is recognised as carcinogenic. This reduces the absorption capacity of folates, compounds that appear to protect against colon and breast cancer. What’s more, ethanol stimulates the production of oestrogen and androgen which circulate in the blood, these hormones contribute significantly to the growth and development of breast, ovary and prostate tissue. Excessive quantities of these hormones increase the risk of developing cancer. Lastly, alcoholic drinks amplify the likelihood of being overweight and obese, which are conditions associated with an increased risk of developing at least 12 forms of cancer.

Wine at the table or spirits at the end of a meal? Beer or cocktails? There is no difference between these different drinks where the link between alcohol and cancer is concerned: all alcohol is a risk factor. It is the amount of ethanol, regardless of what drink it is in, that causes the damage to the body which may give rise to cancer. It follows that most alcohol-related types of cancer occur in people who exceed the recommended level of alcohol consumption: 20 grams per day for men (the equivalent of two 125 ml glasses of wine) and 10 grams per day for women (about one glass of wine).

As we get older, however, our ability to process alcohol gradually decreases, as does the amount of water in the body, so the suggested limits are lower for the elderly. As the years pass, ethanol tends to spend longer in the body, causing greater toxic and carcinogenic effects. As a result, people over the age of 65 are advised not to drink more than one unit of alcohol per day (12 grams of alcohol).

Alcohol doesn’t work alone in raising the risk of cancer. It often interacts with other factors, increasing their harmful effects. Its main partner is smoking: several studies have shown that for people who drink alcohol and are also smokers, the risk of developing cancer of the oral cavity, oesophagus and liver does not just add up, it is multiplied. According to a study conducted by researchers at the Mario Negri Institute in Milan, the results of which were published in the journal Alcohol and Alcoholism in 2013, people who only drink alcohol are 32 percent more likely to develop mouth and throat cancer than the general population. However, when the effects of smoking are added to a drinking habit, the risk increases almost tenfold. Similar conclusions in relation to liver cancer have been recognised for two decades. According to the results of a study published in the International Journal of Cancer, people who drink more than five units of alcohol a day and are also heavy smokers increase their risk of developing cancer more than tenfold.

Can alcohol be drunk during and after treatment for cancer? Although drinking alcohol is not recommended as a general rule, there are no guidelines in this specific case, and whether or not it can be drunk occasionally or in small daily doses varies from patient to patient. The consequences of drinking alcohol while cancer treatment is taking place have mainly been investigated in patients with breast, colorectal and upper digestive tract (oral cavity, pharynx, larynx and oesophagus) cancers. In many cases it was found that drinking alcohol is associated with higher likelihood of recurrence and a lower survival rate. Ethanol may in fact interact with some drugs (e.g., the chemotherapy agents procarbazine and lomustine) or worsen some side effects of these therapies (e.g., mouth ulcers). What’s more, alcohol abuse, when associated with psychological disorders (anxiety and depression are more frequent among cancer patients), may affect how these patients carry out their treatment, worsen their quality of life and weaken the immune system, thus exposing them to a higher risk of infections.

These are the conclusions as things currently stand, new data will enrich our understanding in the future. It is no coincidence that in almost all the studies investigating the impact of drinking alcohol during and after cancer treatment, researchers have emphasised the need for further data before drawing more robust conclusions. In particular, the impact of ethanol on treatments - whether surgery, radiotherapy, chemo- or immunotherapy - needs further investigation. Any decision on whether it is appropriate to drink alcohol during and after treatment should always be made in consultation with the patient’s own doctor. One thing is certain, however: given that alcohol increases the likelihood of developing some kinds of cancer, it also makes the reoccurrence of cancer more likely in those who have already had it.

A correct public health message should always emphasise that alcohol increases the risk of developing chronic diseases including cancer. The most recent scientific reports confirm the trends and findings that can be seen in the relative data and demonstrate that alcohol is one of the main causes of preventable death, illness and disability.