Alcohol can cause at least seven types of cancer, according to research analysis.
Those who drink — especially those who drink a lot — are at risk for oropharynx (located at the top of your throat), larynx, oesophagus, liver, colon, rectum and female breast cancers, according to a review in the Addiction journal from the Society for the Study of Addiction.
"Put very briefly, existing epidemiological evidence supports a causal association of alcohol consumption with cancers at seven sites," review author Jennie Connor of the department of preventive and social medicine at the University of Otago in New Zealand said in the review.
Connor conducted an analysis of 10 years of research by a handful of groups and institutions including the American Institute for Cancer Research and the World Cancer Research Fund.
Connor's conclusions are similar to what is presented by the National Cancer Institute, which asserts on its website that "there is a strong scientific consensus of an association between alcohol drinking and several types of cancer."
The National Cancer Institute, however, shies away from pointing to a causal relationship between alcohol and cancer, with the exception of saying that " alcohol consumption is an independent risk factor for, and a primary cause of, liver cancer."
Both the review and the institute say a few factors may be behind an alcohol-cancer connection. One is how the ethanol in alcohol breaks down to the toxic acetaldehyde, which can damage DNA. They also say that alcohol might cause levels of estrogen to spike, which is correlated with breast cancer in women.
The National Cancer Institute also points to the possibility that alcohol may stop the body from absorbing nutrients like vitamins A, C, D, E, nutrients in B complex, and carotenoids. Alcohol can also create reactive oxygen species that can harm DNA, protein and fat.
Research also shows a decrease in risk for some types of cancer over time when people stop drinking, according to Connor's review.
Connor's review was intended to clarify the "unclear and conflicting messages in the media" and to show "there is increasing research evidence about the causal role of alcohol in cancer," she said in the report.
Some, however, have taken issue with Connor's eagerness to prove cause and effect.
Sam Zakhari, Distilled Spirits Council senior vice president of scientific affairs released the following after Connor's review was published.
"To declare that alcohol definitively causes cancer based upon cherry-picked epidemiology articles lacks scientific credibility. As the articles author Jennie Connor appropriately points out in her own words, 'proof is impossible in epidemiology.' "
"Based on my own 40-year career as a biomedical scientist, including 26 years at the National Institute of Alcohol Abuse and Alcoholism, the science regarding cancer and alcohol consumption is far from settled. In fact, the existing epidemiological studies do not demonstrate causation, nor do they account for the multitude of confounding factors.
"This is particularly true for moderate consumption. For example, there are some studies that suggest an association between moderate alcohol consumption and an increased risk of breast cancer. However, there also are numerous studies that show no association."
Zakhari, formerly with the National Institute on Alcohol Abuse and Alcoholism's division of metabolism and health effects added, "Cancer is a complex disease that is not yet entirely understood and requires more research."
"If anyone has questions regarding alcohol and health, they should discuss the potential risks and potential benefits of consuming alcohol with their physician. Together, they can determine what is best based on individual risk factors including family history, genetics and lifestyle."
Connor, perhaps anticipating criticism, added near the end of her study that "there will be orchestrated attempts to discredit the science and the researchers, and to confuse the public. The stakes are high for alcohol industries when there is no argument, on current evidence, for a safe level of drinking with respect to cancer."
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