Alcohol drinking has long been known to cause cancers of the oral cavity, pharynx, larynx, oesophagus, and liver (IARC Monographs Volume 44, 1988). The addition of breast cancer and colorectal cancer, two of the most common cancers worldwide, to this list indicates that the burden of cancer attributable to alcohol consumption is higher than previously thought. "The scientific evidence relating alcohol drinking to an increased risk of cancer continues to grow as does the contribution of alcohol drinking to the global cancer burden. The clear association with increased risk of breast cancer associated with even modest levels of alcohol drinking is a major concern particularly in view of the changing drinking patterns of women in many countries. Public Health action against alcohol consumption, especially excessive alcohol consumption, needs to be stepped up", said Dr Peter Boyle, Director of the International Agency for Research on Cancer (IARC), the cancer research agency of the World Health Organization.
This is the newest evaluation from the IARC Monographs programme
In February, 2007, 26 scientists from 15 countries met at IARC in Lyon, France, to reassess the carcinogenicity of alcoholic beverages. This assessment will be published in volume 96 of the IARC Monographs. A summary of the meeting appears today in The Lancet Oncology (Carcinogenicity of alcoholic beverages, Robert Baan et al., Policy Watch, The Lancet Oncology, Volume 8, Issue 4 , April 2007, Pages 292-293) and on the Monographs programme website.
Alcohol one of the top-10 risks for health
Although moderate alcohol consumption has some health benefits, the WHO has identified alcohol drinking as one of the top-10 risks for global burden of disease. In 2002, more than 1900 million people (>=15 years of age) around the world were estimated to be regular consumers of alcoholic beverages, with an average daily intake of 13 g of ethanol (about one drink).
Consumption highest in Europe - and increasing in Asia
In general, men drink alcohol more often and in larger quantities than women do. On the basis of production data, per-capita consumption is highest in eastern Europe. In Africa, South America, and Asia, alcohol consumption is comparatively lower, but a large proportion of alcohol is produced locally and remains unrecorded. Over the past 40 years, alcohol consumption has remained stable in most regions of the world, except in the western Pacific region-predominantly China-where it has increased about five-fold.
The Working Group reviewed the epidemiological publications on the possible association between alcohol consumption and cancer at 27 anatomical sites.
For the following cancers a causal association with alcohol drinking has been established:
Cancers of the oral cavity, pharynx, larynx and oesophagus
Many studies of different design and in different populations around the world have consistently shown that regular alcohol consumption is associated with an increased risk for cancers of the oral cavity, pharynx, larynx, and oesophagus. Daily consumption of around 50 g of alcohol increases the risk for these cancers two- to three-fold, compared with the risk in non-drinkers.
A large number of cohort and case-control studies provide strong evidence that the consumption of alcohol is an independent risk factor for primary liver cancer. Cirrhosis and other liver diseases often occur before the cancer becomes manifest and patients with these disorders generally reduce their alcohol intake. Therefore, the effect of alcohol consumption on the risk for liver cancer is difficult to quantify.
More than 100 epidemiological studies that assessed the association between alcohol consumption and breast cancer in women consistently found an increased risk with increasing alcohol intake. A pooled analysis of 53 studies on more than 58 000 women with breast cancer showed that daily consumption of about 50 g of alcohol is associated with a relative risk of about 1.5 (95% confidence interval 1.3-1.6), compared with that in non-drinkers. Even for regular consumption of 18 g of alcohol per day, there is a small but statistically significant increase in relative risk.
The association between alcohol consumption and colorectal cancer has been investigated in more than 50 prospective and case-control studies. Pooled results from eight cohort studies and data from recent meta-analyses provide evidence for an increased relative risk of about 1.4 for colorectal cancer with regular consumption of about 50 g of alcohol per day, compared with that in non-drinkers. This association seems to be similar for colon cancer and for rectal cancer.
Relative Risk increase for consumption of 50 g/day
|Oral Cavity, Pharynx, Larynx, Oesophagus
Difficult to quantify
Furthermore, in populations that are genetically deficient in the activity of an enzyme involved in the metabolism of ethanol, much higher risks for cancer, particularly oesophageal cancer, after alcohol consumption have been reported than in populations with a fully active enzyme. This enzyme deficiency, a condition that is particularly prevalent in certain eastern-Asian populations, causes a strong facial flushing response, physical discomfort, and severe toxic reactions.
Risk linked to alcohol, not to type of drink
As these associations were observed with different types of alcoholic beverages, and given the carcinogenicity of ethanol in animals, ethanol in alcoholic beverages was classified as "carcinogenic to humans (Group 1)".
Alcohol + Tobacco = multiplied risk
The adverse effects of drinking and smoking do not simply add up, but seem to be multiplicative.
"The take home message is simple" concluded Dr Boyle: "If you drink alcohol you should drink in moderation and you should certainly not smoke tobacco under any circumstances."
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