Even light and moderate drinking (up to one drink a day for women and up to two drinks a day for men) is associated with an increased risk of certain alcohol related cancers in women and male smokers, suggests a large study published by The BMJ today.
Overall, light to moderate drinking was associated with minimally increased risk of total cancer in both men and women.
However, among women, light to moderate drinking (up to one drink per day) was associated with an increased risk of alcohol related cancer, mainly breast cancer.
Risk of alcohol related cancers was also higher among light and moderate drinking men (up to two drinks per day), but only in those who had ever smoked. No association was found in men who had never smoked.
Heavy alcohol consumption has been linked to increased risk of several cancers.
However, the association between light to moderate drinking and overall cancer risk is less clear. The role of alcohol independent of smoking has also not been settled.
So a team of US researchers based at Harvard T.H. Chan School of Public Health and Brigham and Women's Hospital in Boston, set out to determine whether light to moderate drinking is associated with an increased risk of cancer.
They used data from two large US studies that tracked the health of 88,084 women and 47,881 men for up to 30 years. They assessed risk of total cancer as well as known alcohol related cancers including cancer of the the colorectum, female breast, liver, oral cavity, pharynx, larynx and esophagus.
Light to moderate drinking was defined as up to one standard drink or 15g alcohol per day for women and up to two standard drinks or 30g alcohol per day for men. One standard drink is roughly equivalent to a small (118ml) glass of wine or a 355ml bottle of beer.
Influential factors, such as age, ethnicity, body mass index, family history of cancer, history of cancer screening, smoking, physical activity and diet were also taken into account.
During the follow-up period, a total of 19,269 and 7,571 cancers were diagnosed in women and men, respectively. The researchers found that overall, light to moderate drinking was associated with a small but non-significant increased risk of total cancer in both men and women, regardless of smoking history.
For alcohol-related cancers, risk was increased among light and moderate drinking men who had ever smoked, but not among men who never smoked. However, even in never smoking women, risk of alcohol-related cancers, mainly breast cancer, increased even within the range of up to one drink a day.
This large study sheds further light on the relationship between light to moderate drinking and cancer, says Dr Jürgen Rehm at the Centre for Addiction and Mental Health in Toronto, in an accompanying editorial.
More research is needed to explore the interaction between smoking and drinking on risk of cancer, he says. But, roughly speaking, women should not exceed one standard drink a day and men should not exceed two standard drinks a day.
Finally, people with a family history of cancer "should consider reducing their intake to below recommended limits or even abstaining altogether, given the now well established link between moderate drinking and alcohol-related cancers," he concludes.