Two or More Drinks a Day Increases Colorectal Cancer Risk

New data suggest that individuals who drink moderate amounts of alcohol, defined as 2 or 3 drinks a day, have an increased likelihood of developing colorectal cancer. The findings also support prior evidence of a causal relationship between a high alcohol intake and increased colorectal cancer risk.

Veronika Fedirko, MD, of the International Agency for Research on Cancer (IARC) in Lyon, France, and colleagues conducted a metaanalysis involving 27 cohort and 34 case-control studies published before May 2010 on alcohol consumption and colorectal cancer.

“The results from this largescale meta-analysis have important public health implications, given the large number of women and, especially, men consuming alcohol and the high incidence of colorectal cancer worldwide and in developed countries, in particular,” reported Fedirko and colleagues.

According to the World Health Organization (WHO), roughly 2 billion people worldwide consume alcohol beverages—an average of 6.2 liters of ethanol per adult per year—on a regular basis.

The IARC has concluded that alcohol consumption is related to colorectal cancer. However, several questions remain unanswered, including the dose-risk relationship of alcohol and colorectal cancer. It is also unclear whether the effect of alcohol varies for colon and rectal anatomical subsites and whether the effect varies by sex and geographical region.

All studies in the meta-analysis included results for at least 3 categories of alcohol consumption. Light alcohol drinking was defined as the consumption of ≤1 drink per day (≤12.5 g/day of ethanol), moderate drinking as 2 or 3 drinks/day (12.6 to 49.9 g/day of ethanol), and heavy drinking as the consumption of ≥4 drinks/day (≥50 g/day of ethanol).

“The results from this large-scale meta-analysis have important public health implications, given the large number of women and, especially, men consuming alcohol and the high incidence of colorectal cancer worldwide and in developed countries, in particular.”

—Veronika Fedirko, MD

Compared with nondrinkers or occasional alcohol drinkers, moderate and heavy drinking were associated with a 21% and 52% increased risk of colorectal cancer, respectively. Light alcohol consumption was not associated with an increased cancer risk. The investigators also found that the association of alcohol drinking with colorectal cancer did not differ by colon and rectal anatomic subsites.

The association between alcohol drinking and colorectal cancer risk was slightly stronger among Asian populations. The authors suggested that this finding may be a function of the high prevalence among Asians of the slow-metabolizing variant of aldehyde dehydrogenase enzyme, which is associated with increased blood levels of acetaldehyde after alcohol ingestion. Nongenetic factors, such as body composition, may also play a role.

Fedirko and colleagues said that the findings mean that public health recommendations for colorectal cancer prevention should include limiting consumption of alcoholic beverages. However, the results need to be interpreted with caution given that high alcohol intake may be associated with behaviors that predispose to colorectal cancer, such as cigarette smoking, unhealthy diet, and low physical activity.

Fedirko V, Tramacere I, Bagnardi V, et al. Alcohol drinking and colorectal cancer risk: an overall and dose-response metaanalysis of published studies. Ann Oncol. 2011 Feb 9. doi:10.1093/annonc/ mdq653. [Epub ahead of print]