This week, from 23rd to 29th June 2025, is World Cancer Research Fund’s annual Cancer Prevention Action Week – and this year, their focus is on highlighting the links between alcohol and cancer. Despite persistent myths suggesting moderate alcohol consumption may be safe – or even beneficial – the unfortunate reality is that alcohol is a carcinogen. Not only that, its impact is not limited to one or two cancer types but extends across at least seven different forms, with the evidence now deemed strong and conclusive.
Understanding the Carcinogenic Nature of Alcohol
The International Agency for Research on Cancer (IARC), a specialised agency of the World Health Organization (WHO), classifies alcoholic beverages and the acetaldehyde derived from alcohol metabolism as Group 1 carcinogens. This is the highest classification available and places alcohol in the same category as tobacco and asbestos. The mechanism behind this risk is now well understood: when alcohol is consumed, it is metabolised by the body into acetaldehyde, a toxic compound that causes mutations in DNA and inhibits cellular repair processes. This damage creates the perfect storm for cancerous cells to develop and proliferate.
The Seven Cancers Strongly Linked to Alcohol
Alcohol has been found to increase the risk of the following seven types of cancer:
- Bowel (Colorectal) Cancer: In the UK, about 6% of bowel cancer cases are linked directly to alcohol consumption. Acetaldehyde’s DNA-damaging properties, coupled with alcohol’s pro-inflammatory effects on the gut lining, elevate the risk. Alcohol also interferes with folate metabolism, a B vitamin essential for DNA synthesis and repair, further compounding the problem. Studies suggest a dose-response relationship, meaning the more alcohol consumed, the higher the risk.
- Breast Cancer: This is the most common cancer among women, and evidence strongly supports a link with alcohol. Alcohol increases oestrogen levels, which in turn stimulates the growth of oestrogen-receptor-positive breast cancer cells. Even light drinking – defined as less than one drink per day – has been associated with a measurable increase in breast cancer risk. This is particularly concerning given the widespread consumption of alcohol among women around the world.
- Liver Cancer: Chronic alcohol use leads to liver inflammation, fatty liver disease, and eventually cirrhosis – a well-known precursor to liver cancer. The liver, responsible for metabolising alcohol, bears the brunt of its toxic effects. Over time, these processes cause genetic mutations and damage that can lead to hepatocellular carcinoma, the most common form of liver cancer.
- Oesophageal Cancer: Alcohol, particularly when combined with smoking, substantially increases the risk of oesophageal cancer, especially the squamous cell type. The synergistic effect of these two risk factors exacerbates mucosal damage in the oesophagus, making it particularly susceptible to cancerous changes.
- Mouth Cancer: The oral cavity is directly exposed to alcohol and its metabolites, making it a high-risk site for cancer development. Alcohol acts as a solvent, enhancing the penetration of other carcinogens – especially tobacco – into the mucosal lining. It also causes dehydration of cells in the mouth, which may facilitate the absorption of carcinogens.
- Pharyngeal and Laryngeal Cancers: These upper respiratory tract cancers are significantly more common in individuals who drink alcohol, especially in combination with tobacco use. Alcohol irritates the mucous membranes and increases cell turnover, thereby heightening vulnerability to DNA damage and mutation.
- Stomach Cancer: Although the evidence is not as strong as for the others listed, several studies suggest a link between heavy alcohol consumption and stomach cancer. Alcohol may promote Helicobacter pylori infection and chronic inflammation in the gastric lining, both of which are risk factors for cancer.
Mechanisms That Explain Alcohol’s Carcinogenic Effects
Beyond acetaldehyde-induced DNA damage, alcohol affects various physiological and biochemical processes that contribute to cancer risk:
Hormonal Disruption
Alcohol consumption can increase levels of circulating hormones like estrogen and insulin, both of which can promote cellular proliferation – a hallmark of cancer.
Oxidative Stress
Alcohol metabolism produces reactive oxygen species (ROS), which can damage cellular proteins, lipids, and DNA.
Nutritional Deficiencies
Chronic alcohol use can lead to deficiencies in essential nutrients like folate, zinc, and vitamins A, C, D, and E, all of which play critical roles in DNA repair and immune function.
Weight Gain and Obesity
Alcohol is calorie-dense, and frequent consumption contributes to weight gain – a known risk factor for several types of cancer, including postmenopausal breast cancer and colorectal cancer.
Alcohol, Smoking, and Cancer: A Dangerous Trio
Surprise, surprise – the relationship between alcohol and cancer becomes even more lethal when combined with smoking. Both substances independently increase the risk of cancer, but when used together, their carcinogenic effects multiply. Alcohol enhances the mucosal penetration of tobacco-derived carcinogens, while also suppressing the body’s ability to detoxify and repair DNA. This compounding effect significantly increases the risk of cancers in the upper gastrointestinal tract, including the mouth, pharynx, larynx, and oesophagus.
The “Sobering” Message
With the risk of being killjoys, medical professionals have to start hammering home the message to patients about the cancer risks associated with alcohol. This means not only advising on safe drinking levels but also providing support for those looking to reduce or eliminate alcohol intake. Brief interventions in primary care settings, combined with public health campaigns like Cancer Prevention Action Week, can hopefully help to influence public perception and behaviour.
Most of us enjoy the odd drink, and possibly also over-indulge a bit too often, but the bottom line is that there is no safe level of alcohol consumption when it comes to cancer risk. So, the message is clear: reducing alcohol intake reduces cancer risk.
Cancer Prevention Action Week 2025:
The U.S. Department of Health and Human Services (HHS), 15th Report on Carcinogens, Acetaldehyde:
