Today is World Cancer Day, a moment meant not for slogans but for clarity. Alcohol is now firmly established as a cause of cancer, not a marginal or speculative risk. New research, long-term population data, and updated European prevention guidance all point in the same direction. Alcohol increases cancer risk in a dose-dependent way, affects multiple organs, and contributes substantially to the overall cancer burden. While the highest risks are seen with heavier and long-term drinking, the idea that alcohol-related cancer risk is confined to a narrow group of people or a small set of rare cancers no longer holds up.

One of the clearest recent signals on the dangers of sustained heavy drinking comes from a large U.S. study following more than 88,000 adults for over 20 years as part of the National Cancer Institute’s PLCO Cancer Screening Trial. Researchers identified 1,679 cases of colorectal cancer and found that people who consistently drank heavily across adulthood, defined as 14 or more drinks per week, had a 25 percent higher risk of colorectal cancer overall and nearly double the risk of rectal cancer compared with those drinking less than one drink per week. Importantly, the study also found that former drinkers did not carry this elevated risk, suggesting that stopping alcohol use may help reduce long-term cancer risk.

Biology helps explain why this relationship is so consistent. When alcohol is metabolised, it produces acetaldehyde, a toxic compound that can damage DNA. Alcohol also promotes inflammation, oxidative stress, disrupts folate metabolism, and alters gut microbiota, all of which are relevant pathways in cancer development. These mechanisms are not confined to one organ. Alcohol has been linked to cancers of the mouth, throat, oesophagus, stomach, colorectum, liver, and female breast, and risk begins at low levels of consumption before rising steadily as intake increases.

Population-level evidence reinforces the same message. A recent Australian study published in the British Journal of Cancer analysed more than 70 years of national data on alcohol consumption and cancer mortality. The researchers estimated that long-term alcohol exposure contributed to around 45 percent of male upper aerodigestive tract cancer deaths, nearly half of male liver cancer deaths, and a substantial share of colorectal and breast cancer deaths. The burden was highest among people aged 50 and over, reflecting the cumulative effects of decades of drinking. Crucially, the study modelled prevention as well. Reducing average alcohol consumption by just one litre per person per year was associated with measurable reductions in deaths from several major cancers. This is not about individual willpower alone. The authors pointed to proven policy tools, including taxation, availability controls, and marketing restrictions, as the most effective ways to lower cancer mortality at population level.

Against this backdrop, Europe’s main cancer prevention framework has also sharpened its message. The European Code Against Cancer, 5th edition, now advises people to “avoid alcoholic drinks,” replacing the earlier guidance to limit intake. This change is based on comprehensive evidence reviews published in The Lancet Regional Health – Europe and Molecular Oncology, and supported by assessments from the International Agency for Research on Cancer. The authors conclude that there is no safe level of alcohol consumption for cancer risk, that all types of alcoholic drinks can cause cancer, and that even light to moderate drinking accounts for a significant share of alcohol-attributable cancers in the European Union. The updated Code also makes clear that prevention depends on supportive environments, pairing individual advice with policy recommendations that reduce exposure and denormalise alcohol use.

Taken together, these findings mark a shift from ambiguity to precision. Alcohol is not a minor lifestyle factor at the edges of cancer prevention. It is a common, modifiable, and scientifically established cause of cancer. For individuals, the safest option for cancer prevention is to avoid alcohol. For societies, reducing alcohol consumption through effective public policy can prevent disease and save lives. On World Cancer Day, that is not a radical claim. It is what the evidence now says.