Meat consumption has been associated with colorectal cancer in previous studies, but the strength of the association and types of meat involved have not been consistent, according to background information in the article. Few studies have evaluated long-term meat consumption or the relationship between meat consumption and the risk of rectal cancer. Clarifying the role of meat consumption and any subsequent development of colorectal cancer is important because meat is an integral component of diet in the United States and many other countries in which colorectal cancer is common. Per capita annual consumption of beef has increased in the United States since 1993, reversing a previous decrease since 1976.

Ann Chao, Ph.D., of the American Cancer Society, Atlanta, and colleagues examined the relationship between recent and long-term meat consumption and the risk of colon and rectal cancer. The study included 148,610 adults aged 50 to 74 years, residing in 21 states with population-based cancer registries, who provided information on meat consumption in 1982 and again in 1992/1993 when enrolled in the Cancer Prevention Study II (CPS II) Nutrition Cohort. Follow-up from time of enrollment in 1992/1993 through August 31, 2001, identified 1,667 incident colorectal cancers.

The researchers found that high intake of red and processed meat reported in 1992/1993 was associated with higher risk of colon cancer after adjusting for age and energy intake but not after further adjustment for body mass index, cigarette smoking, and other covariates. When long-term consumption was considered, persons in the highest tertile of consumption in both 1982 and 1992/1993 had a 50 percent higher risk of distal colon cancer (a section of the colon near the rectum) associated with processed meat, and those persons with the highest ratio of red meat-to-poultry and fish had a 53 percent increased risk of distal colon cancer, relative to those persons in the lowest tertile at both time points. Long-term consumption of poultry and fish was inversely associated with risk of both proximal and distal colon cancer. High consumption of red meat reported in 1992/1993 was associated with a 71 percent higher risk of rectal cancer, as was high consumption reported in both 1982 and 1992/1993 (43 percent increased risk).

The main strengths of this study are its size, the availability of dietary and other exposure information collected prospectively from respondents at 2 time points, and information on major potential confounders. The sample size allowed us to obtain stable estimates of risk and to show differences by colorectal subsite. Our results demonstrate the potential value of examining long-term meat consumption in assessing risk and strengthen the evidence that prolonged high consumption of red and processed meat may increase the risk of cancer in the distal portion of the large intestine, the authors conclude.

jama