The more alcohol you drink, the more likely you are to develop at least seven types of cancer, oncologists warn.
Drinking - even small or moderate amounts - was especially closely associated with increased risks for esophogeal, mouth, liver, colorectal and breast cancers, and is responsible for more than five per cent of cancers and cancer deaths worldwide.
The American Society of Clinical Oncology (Asco) has never before formally addressed the link between alcohol and cancer, but is now underscoring the importance of controlling "high-risk" alcohol consumption to reducing the risk of cancer.
Asco does suggest strategies for cutting back on drinking, it also advocates for temperate use of alcohol, rather than recommending giving up drinking altogether.
Seven cancers caused by alcohol
• Head and neck
As of 2013, about 73 per cent of Americans reported consuming alcohol, and nearly 13 per cent described their consumption habits as binge drinking, according to a survey published in JAMA Psychiatry in August.
The survey found that alcohol consumption had soared since 2001-2002. Drinking in general was up 11 per cent, high-risk drinking was 30 per cent more common and 50 per cent more people qualified as having a drinking problem.
The CDC recommends that women have no more than one drink a day or eight drinks a week. Men can drink two drinks a day, or 14 a week. But data suggests that many Americans are drinking far more than they should.
Asco cited a review that found "the evidence to be convincing" that alcohol consumption is not just linked to, but is a cause of, mouth, throat, voice box, colorectal, liver and breast cancer.
The report said that there is also now enough evidence to suggest that alcohol is a probably cause of pancreatic, stomach and other cancers.
"The most recent data that I have seen estimated that this was 18,200-21,300 alcohol related deaths in the US in 2009," says study co-author Noelle LoConte, a professor at the University of Wisconsin School of Medicine and Public Health.
There has been some debate over whether alcohol itself, or other elements come the compositions of various alcoholic beverages are cancer-causing. The Asco report puts that debate to bed: "The answer is that associations between alcohol drinking and cancer risk have been observed consistently regardless of the specific type of alcoholic beverage," it says.
Alcohol does not affect each part of the body in the same carcinogenic way, as LoConte explained.
"For head and neck and esophageal cancers, alcohol's breakdown product (acetaldehyde, which is an established carcinogen) touches the tissues directly as one swallows an alcoholic drink and causes cancer," she wrote.
Liver cancer is caused by cirrhosis, which is in turn caused by drinking. When cirrhosis develops, healthy liver cells are replaced by damaged scar tissue cells, which can become cancer cells.
Alcohol, LoConte says, "interferes with the absorption of folate, which is a critical step in the development of colon cancer".
When a woman's estrogen levels become abnormally high, the hormone puts her at higher risk for breast cancer. Alcohol has been shown to increase estrogen levels.
In fact, Asco reports that women who drank even one drink of beer or wine (which have significantly lower alcohol contents than liquors) were five per cent more likely to develop premenopausal breast cancer, and nine per cent more likely to develop the cancer after menopause.
"If you don't drink, don't start," says LoConte, and "if you do drink try to stay under the recommendations of 1 or less per day for women and 2 or less per day for men."
But if you drink more than that, all hope is not lost. "If you drink more, drinking less will definitely reduce your risk," she says. "If you move from a 'heavy drinker' to a 'moderate drinker' your risk of all of the cancers does go down."