High-fruit, low-meat diet reduces colon cancer risk, UNC study finds

March 20, 2007

People who eat a high-fruit, low-meat diet have about half the risk of developing precancerous colon polyps than those who eat a high-meat diet, University of North Carolina at Chapel Hill researchers have found.Surprisingly, the study also found that people who eat a high-vegetable, moderate-meat diet have essentially the same risk of developing a colorectal adenoma as the high-meat group, said Dr. Gregory Austin, a clinical fellow in gastroenterology at UNC Hospitals and lead author of the study, which is published in the April 2007 issue of the Journal of Nutrition.

“People should eat more fruit and less meat. That’s the key finding here,” Austin said. “Eating a high-fruit, low-meat diet does seem to decrease your risk of developing a precancerous colorectal polyp.”

At the same time, people should not take this study as an indication that vegetable consumption is not helpful, Austin said. The higher meat consumption in the high-vegetable, moderate-meat group may have led to the increased risk of developing an adenoma (a precancerous polyp) compared to the high-fruit, low-meat group.

Another surprising finding, Austin said, was that the high-fruit, low-meat group consumed more total calories than the high-vegetable, moderate meat group. As expected, the high-meat group consumed the largest amount of total calories.

The results are based on analysis of dietary patterns and lifestyle data collected from 645 patients who had a colonoscopy at UNC Hospitals. All of the participants were between 30 and 80 years old and had no personal history of colon cancer, precancerous polyps, inflammatory bowel disease or previous colon resection. Both men and women were included and the average age of study participants was 58. Among all participants, 179 had one or more adenomas.

Austin and colleagues collected information about the participants’ eating habits by using a food frequency questionnaire that records portion sizes for 124 food items developed by the National Cancer Institute. Participants provided information about their eating habits for the year leading up to their colonoscopy.

An initial analysis of the questionnaire data revealed three distinct clusters, or groups of dietary patterns. The largest group was the high-meat cluster, which included 53 percent of participants, whose eating habits most closely matched the typical American diet. The second-largest group was the high-fruit, low-meat cluster, which included 28 percent of participants. The smallest group was the high-vegetable, moderate-meat cluster, representing 18 percent.

The researchers adjusted their statistical analysis to control for differences in total calories consumed and for other potentially confounding variables. These included age; body mass index (BMI); race; use of non-steroidal anti-inflammatory drugs such as aspirin; sex; alcohol consumption; and if the participant smoked (if so, the number of years the participant smoked was factored into the analysis).

The final results showed that participants in the high-vegetable, moderate-meat cluster were more than twice as likely than participants in the high-fruit, low-meat cluster to have an adenoma. Participants in the high-meat group were 1.7 times more likely to have an adenoma than those in the high-fruit, low-meat cluster.

These results show a clear protective benefit for the high-fruit, low-meat diet, Austin said, while the other two groups have essentially twice the risk.

Dr. Linda Adair

Dr. Jessie Satia

Austin’s co-authors, all from UNC, are Dr. Linda S. Adair and Dr. Jessie A. Satia, both from the department of nutrition in the School of Public Health; and Dr. Joseph A. Galanko and Christopher F. Martin, both from the division of gastroenterology and hepatology in the School of Medicine. Senior author is Dr. Robert S. Sandler, chief of the division of gastroenterology and hepatology.

School of Medicine contact: Stephanie Crayton, (919) 966-2860, scrayton@med.unc.edu.

News Services contact: Clinton Colmenares, (919) 843-1991, clinton_colmenares@unc.edu.