Writing in the journal Addiction, Jennie Connor at the University of Otago in New Zealand says alcohol is estimated to have caused about half a million deaths from cancer in 2012 alone – 5.8 per cent of cancer deaths worldwide. She found evidence of a link between drinking and cancer of the mouth and throat, larynx, oesophagus, liver, colon, bowel and breast.
“We see the risk increasing as the amount of alcohol consumed increases, and we agree that there is solid evidence to conclude that alcohol consumption directly causes cancer,” says Susannah Brown, science programme manager for the World Cancer Research Fund.
Although the highest risks are from heavy drinking, people who drink at low levels are still at risk. According to Connor, there is no safe level of drinking when it comes to cancer.
This sentiment is in line with UK guidance. In January, the UK’s chief medical officers said that no level of regular drinking is without risks to health, and reduced the weekly recommended limit for men down to 14 units, to match advice for women.
The exact biological reasons for why alcohol causes cancer remain unclear. One theory is that alcohol can damage DNA, causing harmful mutations.
University of Otago researcher Professor Jennie Connor’s new review of epidemiological evidence supports a causal association between alcohol consumption and cancers at seven sites in the body: oropharynx, larynx, oesophagus, liver, colon, rectum and female breast.
This is a stronger statement than the long-recognised association between alcohol and cancer. An association means there is a relationship of some kind between the two variables. A causal association means there is evidence that alcohol consumption directly causes cancer.
Professor Connor’s review is published online today by the scientific journal Addiction.
The causal link was supported by evidence for a dose-response relationship, at least partial reversal of risk when alcohol consumption is reduced, statistical adjustment for other factors that might explain the association, and specificity of the association with some cancers and not others.
The epidemiological evidence for these conclusions comes from comprehensive reviews undertaken in the last 10 years by the World Cancer Research Fund and American Institute for Cancer Research, the International Agency for Research on Cancer, the Global Burden of Disease Alcohol Group, and the most recent comprehensive meta-analysis undertaken by Bagnardi and colleagues*, building on meta-analyses of the effect of alcohol on single cancers.
Professor Connor’s review cites evidence that alcohol caused approximately half a million deaths from cancer in 2012, 5.8 per cent of cancer deaths worldwide. The highest risks are associated with the heaviest drinking, but a considerable burden is experienced by drinkers with low to moderate consumption.
The review also finds the current evidence that moderate drinking provides protection against cardiovascular disease is not strong.