In Canada, in 2010, some 173,800 Canadians were diagnosed with cancer and more than 76,000 died from it. Alcohol is among the top 3 leading risk factors for death from cancer worldwide.
And yet Canadians as a whole are unaware that alcohol can lead to cancer.
In a survey conducted in 2008 which asked Canadians about their awareness of risk factors for cancer, only 33% of us thought drinking alcohol was linked to an increased risk of cancer. Canadians were more likely to associate alcohol with diabetes or heart disease.
Evidence linking alcohol to cancer has been present since the 1990s. A review by the World Cancer Research Fund found good evidence that alcohol increases the risk of cancer of the esophagus, mouth, throat, breast and colon. In addition it increases the risk of liver cancer.
Research does support the concept of a dose-response relationship between alcohol and cancer, meaning the more alcohol one drinks, the higher the risk of cancer. In addition, the WCRF does not identify a safe level of alcohol consumption. Studies have shown that women who average 12 g of alcohol a day – the equivalent of about one drink – had a 10% increase risk of breast cancer.
The percentage of Canadians who exceed the low risk is increasing steadily in Canada. The rising trend is seen in all age groups and as income increases so does alcohol consumption.
In this week’s issue of the CMAJ is an analysis revisiting guidelines for sensible drinking. The article points out that guidelines for sensible drinking are typically based on the short term effects of consuming alcohol such as the social and psychological problems but often disregard the known dose response relationship between alcohol and cancer risk.
In 1984, the British Health Education Council, according to this review, described sensible drinking as 18 standard drinks per week for men and 9 standard drinks per week for women. In 1987, those limits were raised to 21 and 14 drinks per week.
Studies have shown that ethanol and its metabolite acetaldehyde are carcinogenic. They also increase the permeability of other carcinogens such as tobacco. It also interferes with the metabolism of folate which can also lead to an increaser risk of colorectal cancer. Alcohol is also known to modify sex hormones which influences the development of breast cancer.
Given that there is no safe level for risk of cancer, there is no safe limit of exposure that can be recommended. This advice is often reflected against the suggestion that there is a beneficial effect of moderate alcohol consumption in preventing cardiovascular disease. The WHO however in reviews of studies have stated “there is no merit in promoting alcohol consumption as a preventive strategy.”
Our guidelines in Canada, written in 1997, state that low risk starts at zero drinks for the lowest level of risk for alcohol-related problems Levels above 0, with up to 2 drinks per day and totalling 9 drinks per week for women and 14 drinks per week for men are considered so-called “low risk” and not NO risk.
It must be remembered that these kinds of guidelines do not apply to those who have a family history of cancer. In 2011, we expect that new guidelines will be released here in Canada.