Alcohol Consumption and the Risk for Colorectal Cancer

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The summary below is from the full report titled "Alcohol Intake and Colorectal Cancer: A Pooled Analysis of 8 Cohort Studies." It is in the 20 April 2004 issue of Annals of Internal Medicine (volume 140, pages 603-613). The authors are E. Cho, S.A. Smith-Warner, J. Ritz, P.A. van den Brandt, G.A. Colditz, A.R. Folsom, J.L. Freudenheim, E. Giovannucci, R.A. Goldbohm, S. Graham, L. Holmberg, D.-H. Kim, N. Malila, A.B. Miller, P. Pietinen, T.E. Rohan, T.A. Sellers, F.E. Speizer, W.C. Willett, A. Wolk, and D.J. Hunter.

What is the problem and what is known about it so far?

Colorectal cancer is cancer of the colon (large intestine) or rectum and is one of the most common types of cancer in the United States. Whether drinking alcohol increases a person's risk for colorectal cancer has been uncertain. Some studies have shown that alcohol increases colorectal cancer risk, and others have not. Studies have been too small to give definite answers or to see whether certain alcoholic beverages influence colorectal cancer while others do not. They have also been too small to determine whether alcohol intake is associated with the risk for cancer in certain parts of the large intestine or rectum. It would be useful to know whether alcohol increases colorectal cancer risk so that people could adjust alcohol intake accordingly.

Why did the researchers do this particular study?

To find out whether alcohol intake is associated with the risk for colorectal cancer, whether different alcoholic beverages influence risk differently, and whether alcohol is associated with cancer in particular parts of the large intestine.

Who was studied?

Rather than do a new study, the authors combined data from 8 previous studies of the relationship of alcohol intake with the future development of colorectal cancer. These studies included a total of 489,979 people.

How was the study done?

At the beginning of each study, study participants were asked a question about alcohol intake. Researchers then followed participants for 6 to 16 years to see who developed colorectal cancer. The authors combined this information from all of the studies. They also analyzed information about the type of alcoholic beverages people drank and the location of any colorectal tumors that developed.

What did the researchers find?

Of the 489,979 people in the 8 studies, 4687 developed colorectal cancer. Compared with people who reported drinking no alcohol, people who reported drinking more than 30 grams of alcohol per day (the equivalent of 2 average-size drinks) had a small increase in risk for colorectal cancer. The increase in risk was highest in people who drank more than 45 grams of alcohol per day (> 3 average-size drinks). The authors could not find differences in colorectal cancer risk by the type of alcoholic beverages people drank. In addition, the 8 studies showed no relationship between alcohol intake and the location of colorectal cancers within the intestine. In addition, the 8 studies showed no relationship between alcohol intake and the location of colorectal cancer in the intestine.

What were the limitations of the study?

Study participants reported alcohol intake only once at the beginning of the study; intake could have changed over time. Risk was increased only among people with the highest levels of alcohol intake, an amount reported by only a small fraction of the people studied.

What are the implications of the study?

People who drink more 30 grams of alcohol per day (and especially those who drink more than 45 grams per day) appear to have a slightly higher risk for colorectal cancer. Doctors and patients should consider this risk when weighing the risks and benefits of alcohol.