Alcohol may be a social lubricant but WHO and Public Health England say it can cause cancer. Last week the alcohol industry was accused of downplaying the link between alcohol and the increased risk of seven cancers: mouth, throat, oesophagus, liver, breast, rectum and colon. A research paper in Drug and Alcohol Review found that “responsible drinking” information funded by the alcohol industry tends to push the message that only heavy drinking increases the risk of these cancers. But the paper says the risk starts with low levels of drinking, even though the risk itself is low. So is the recommended number of alcohol units a week – 14 – too high?

The solution

Even less than 1.5 units a day – a small glass of wine – can increase the risk of mouth, throat, oesophagus and breast cancer (in women), according to a UK government committee. While the toll of heavy drinking on the liver and pancreas is well known, the link to cancers, especially breast and colorectal, is less so. There are more than 100 epidemiology studies showing an association between breast cancer and alcohol, the risk increasing with less than one daily glass of wine. Research at Harvard found that while light to moderate drinking was not significantly associated with an increased risk for men (unless they smoked), it did increase the risk of breast cancer for women.

Edward L Giovannucci, professor of nutrition and epidemiology at Harvard School of Public Health and the lead author of the report, says that the increase in risk is modest. And there are some health benefits from occasional drinking that make the true risk to health harder to quantify. He points out other research that shows that one drink per day reduces the risk of diabetes for women. “So the overall effect on health for women might still be positive,” he says. “For colorectal cancer, the risk for men and women is low until you reach more than two drinks per day.”

There are also individual genetic differences in metabolising alcohol that can increase the risk of cancer. Ethanol in alcoholic drinks is broken down into acetaldehyde, which is toxic to cells, damaging DNA and proteins. Some people have genetic variations that are less effective at getting rid of acetaldehyde, and they may have a higher risk of oesophageal cancer.

Giovannucci says that overall he wouldn’t recommend drinking alcohol to improve your health. “But if one enjoys a glass or occasionally two a day as part of a healthy diet, and doesn’t smoke, I think the increased risk of cancer is small,” he says. “For those with a family history of colorectal or breast cancer, I’d suggest not drinking or not exceeding one glass per day.”

• This article was amended on 3 October 2017. An earlier version said alcohol increased the risk of seven cancers but only gave six. Rectal cancer has been added to this list.

