Just one alcoholic drink a day may increase the risk of cancer, according to a new study, which estimates that light drinking is responsible for 34,000 deaths a year worldwide.
New research based on more than 150,000 men and women shows that light drinking increases the likelihood of cancer of the mouth, pharynx, oesophagus and breast.
One drink a day increased the risk of cancer of the oesophagus by almost a third, according to the study being reported in the Annals of Oncology, which analysed data from more than 200 research projects. Low alcohol intake increased the risk of oral cavity and pharynx cancer by 17 per cent, and breast cancer in women by 5 per cent.
"Alcohol increases the risk of cancer even at low doses," say the researchers. "Given the high proportion of light drinkers in the population, and the high prevalence of these tumours, especially of breast cancer, even small increases in cancer risk are of great public health relevance."
When it comes to enjoying your favourite drink and looking after your health, advice has often been complicated. Evidence suggests that drinking in moderation may decrease the risk of heart disease, type-2 diabetes and dementia, leading many to believe a glass of wine a day is good for you.
But the damaging effects of drinking are well known. An estimated 2.2 million deaths a year worldwide are linked to alcohol, according to the report, and 3.6 per cent of all cancers are attributable to drinking alcohol.
Until now, almost all the evidence has come from studies that focused on people drinking moderate or large amounts of alcohol, or binge drinkers, and not those who drink less.
In the new study, researchers from the University of Milan and other centres in the US, France, Canada, Iran and Sweden, estimated that, in one year alone, 24,000 deaths from oesophageal cancer, 5,000 from oral and pharyngeal, and 5,000 from breast cancer, were due to light drinking.
The study defined light drinking as up to one drink a day or 12.5g or less of ethanol.
Data on 92,000 light drinkers and 60,000 non-drinkers was used to calculate the overall cancer risk.
No link was found with other cancers that have been associated with heavier drinking, including colon, liver and larynx.
Professor Peter Johnson, Cancer Research UK's chief clinician, said: "This study adds to the evidence linking alcohol consumption to several types of cancer, and confirms that even light drinkers have a small but definite increase in the risk, particularly for those parts of the body, such as the throat and oesophagus, that come into direct contact with alcohol.
"People who wish to minimise their risk of cancer can help by cutting down on their drinking."
Just why light intake increases the risk of some cancers and not others, is unclear. The researchers suggest that with cancer of the mouth, pharynx and oesophagus it may be because the alcohol comes into direct contact with the affected tissue. They suggest the rise in risk for breast cancer may be associated with increased levels of oestrogen, or higher levels of insulin-like growth factors that are produced by the liver after drinking alcohol.