A major new genetic study has cast doubt on the long-held belief that alcohol consumption directly increases the risk of developing breast cancer, while simultaneously confirming its strong link to several other cancer types. The research, led by teams from the University of Cambridge and Sweden's Karolinska Institute, challenges aspects of established public health guidance.
Genetic Analysis Questions Established Links
Published in the journal BMC Medicine on Tuesday 16 December 2025, the study employed a technique called Mendelian randomisation. This method examines genetic variants known to influence a specific trait—in this case, genes linked to whether people tend to drink more or less alcohol. By analysing genetic data from 1.4 million people across long-term studies in the UK, US, and Finland, researchers sought more robust evidence than traditional observational studies can provide.
Professor Stephen Burgess, a statistician from the Medical Research Council Biostatistics Unit at Cambridge who oversaw the study, stated: "Our investigation confirms the harmful effect of alcohol consumption on cancer risk, but suggests that alcohol only increases cancer risk in body parts with direct exposure to alcohol." He added, "In particular, we did not see evidence supporting an effect of alcohol consumption on breast cancer risk, contradicting previous research."
Confirmed Risks and a Stark Mortality Finding
The genetic analysis found a clear association between genes linked to higher alcohol consumption and increased risk for cancers in tissues that have direct contact with alcohol. These included cancers of the head, neck, oesophagus, and bowel. This aligns with warnings from the International Agency for Research on Cancer, which lists alcohol as a risk factor for at least seven cancer types.
A particularly striking finding emerged from the UK data set: genetically predicted alcohol consumption was linked with a 44 per cent increased risk of cancer death overall. This underscores the significant general health burden posed by alcohol.
Expert Interpretation and Ongoing Caution
Dr Susanna Larsson, the epidemiologist from the Karolinska Institute who led the analyses, explained the breast cancer discrepancy: "We could not confirm the link between alcohol consumption and breast cancer risk in our genetic study. This could mean the true effect is very small, or that previous findings were influenced by other factors, such as hormone use, which are difficult to fully account for in observational studies."
Dr Siddhartha Kar, a physician-scientist at Cambridge, noted that while the cancer impact may be more limited to directly exposed sites, alcohol's broad harm to society—increasing risks of heart disease, liver disease, dementia, and violence—remains undisputed.
Health charities responded with caution. Dr Claire Knight of Cancer Research UK emphasised that "decades of high-quality research" still link alcohol to breast cancer, advising that cutting down reduces risk. Sally Kum of Breast Cancer Now acknowledged the new findings but recommended people still follow national guidance of no more than 14 units per week, spread over three days, due to alcohol's other health impacts.
The study highlights the complexity of cancer causation, where risk is influenced by genetics, lifestyle, and environment, and reinforces the value of advanced genetic methods in untangling these intricate relationships.
