Alcohol is associated with 5.5 per cent of all new cancers and 5.8 per cent of all cancer deaths worldwide, including cancers of the breast, larynx, liver, colon, esophagus, and head and neck, according to statement released Tuesday by the American Society of Clinical Oncology.

Even light drinking (defined as one drink a day) increases risk -- but the greatest risk exists with heavy drinkers (defined as four or more drinks in one sitting):

  • Light drinking increases your risk of head and neck cancers by 13 per cent, while heavy drinking increases risk by over 500 per cent.
  • Breast cancer risk increases 4 per cent with light drinking, and rises 61 per cent with heavy drinking.

Alcohol causes damage in different ways. In one, it converts into a carcinogen called acetaldehyde, which can stop cells from repairing DNA damage, explains lead author Dr. Noelle K. LoConte of the University of Wisconsin.

“For the liver it is a bit different: alcohol causes cirrhosis and it is actually the cirrhosis that causes the cancer,” she says.

“And with colon cancer, alcohol seems to interfere with the way folate is absorbed, which is a known precursor in the path to developing cancer in the colon. And in female breast cancer, (alcohol) affects the levels of female hormones in the body, and by adjusting the levels of estrogen in particular, it increases risk of breast cancer.”

The real concern is excessive and specifically binge drinking (which is defined as eight or more drinks per week or three or more drinks per day for women, or 15 or more drinks per week or four or more drinks a day for men).

The authors write that the number of adults who binge drink has been increasing during the past decade.

“With alcohol we are not saying don’t drink ever. We are saying drink in moderation and really avoid binge drinking,” says LoConte.

“But a little bit of alcohol here or there is probably OK. Even one drink a day, every day, your risk of breast cancer goes up a tiny amount but not a lot. It is really the heavy drinkers over a long period of time that we need to worry about.”

The researchers add that the benefits of alcohol -- especially the widely held belief that red wine improves cardiovascular health -- has likely been overstated and doctors should not recommend alcohol consumption to prevent cardiovascular disease.

The doctors say there is a need for public education about drinking and cancer risks, especially among general practitioners who may lack knowledge about the link.