A meta-analysis of case-control and cohort studies on the association of alcohol consumption with colorectal cancer was carried out, based on 22 studies from Asia, 2 from Australia, 13 from Western Europe, and 24 from North America. The paper provides evidence that alcohol, at least at higher levels of consumption, is associated with an increase in the risk of colorectal cancer. Overall, there was no increase in the risk for consumers reporting an average intake of up to 1 drink per day, but an increase (of 21%) for what the authors defined as "moderate drinking" (averaging up to 49.9 g of alcohol – far in excess of all responsible drinking guidelines ). The increase in risk was greater (52%) for consumers of 50 or more grams of alcohol per day.
Forum reviewers thought that this was, in general, a very well-done study that used appropriate statistical techniques for meta-analysis. There were some key concerns, however, including the following: (1) the authors' definition of "moderate drinking" extended well above the usual recommended limits for sensible drinking; effects of consumption in categories of 1 to 2 drinks/day, 2 to 3 drinks/day, etc., were not given; (2) no results were provided according to type of beverage even though many previous studies have shown differences between health effects for consumers of wine, or wine/beer, and other beverages; and (3) no data were available on the pattern of drinking. Many studies have shown that regular, moderate drinking on most days of the week has very different health outcomes than drinking only on week-ends or binge drinking.
Despite these concerns, Forum members agreed that current data indicate that alcohol intake, especially heavier drinking, is associated with an increase in the risk of colorectal cancers. Future studies are needed to help determine if there is a threshold level of alcohol that increases the risk, if there are differences by type of beverage, and if the pattern of drinking (regular versus binge drinking) affects the risk.