The study, published in the journal Addiction on Thursday, found an association between alcohol consumption and cancers in seven sites of the body: the oropharynx, larynx, esophagus, liver, colon, rectum, and female breast. The strongest link was between alcohol and cancers of the mouth and throat.
The research goes on to cite figures which suggest that alcohol led to around half a million cancer-related deaths in 2012, or 5.8 percent of cancer deaths worldwide.
Study author Jennie Connor, of the preventative and social medicine department at New Zealand’s Otago University, said the study shows there is more than a simple link or association between alcohol and cancer, and that there is now enough evidence to prove that drinking is a direct cause of the disease.
“There is strong evidence that alcohol causes cancer at seven sites in the body and probably others,” Connor wrote. “Even without complete knowledge of biological mechanisms [of how alcohol causes cancer], the epidemiological evidence can support the judgment that alcohol causes cancer of the oropharynx, larynx, oesophagus, liver, colon, rectum and breast.”
She added that there is growing evidence to suggest that alcohol is also a likely cause of skin, prostate, and pancreatic cancer, and that current evidence that moderate drinking provides protection against cardiovascular disease is not strong.
The highest risks, according to Connor, are associated with heavy drinking – those who regularly drink five units a day have a 40 percent increased risk.
However, those consuming low to moderate amounts of alcohol are also affected. Connor said campaigns to reduce alcohol consumption should be aimed at everyone to cut down, regardless of their drinking habits.
She admitted, however, that the research has its limitations – particularly because many of the studies relied on people self-reporting their alcohol consumption, and it is not uncommon for people to claim they drink less than they actually do.
Connor said that although the exact reason for why alcohol causes cancer is not understood, scientists believe it’s because a compound that breaks down when alcohol is consumed is responsible for cancer in the mouth, throat, esophagus, and liver. As for breast cancer, it is believed that alcohol may cause cancer by increasing levels of estrogen in the body.
Connor and her team arrived at their conclusions after studying comprehensive reviews undertaken in the last 10 years by the World Cancer Research Fund, the American Institute for Cancer Research, the International Agency for Research on Cancer, the Global Burden of Disease Alcohol Group, and a recent academic analysis titled ‘Alcohol consumption and site-specific cancer risk: a comprehensive dose-response meta-analysis.’