Medical Research: What is the background for this study? What are the main findings?
Dr. Orlich: Colorectal cancer is the second leading cause of death from cancer in the United States. Screening efforts such as colonoscopies have helped save many lives by detecting pre-cancerous polyps and removing them. However, it is even better to prevent cancers from forming in the first place. We call this primary prevention. Diet is a potentially important approach to reduce the risk of developing colorectal cancer. In this analysis, we compared those eating different categories of vegetarian dietary patterns to those eating a non-vegetarian diet. About half of our study population was classified as non-vegetarian, which we defined as eating meat at least weekly. The other half of our population we called vegetarian and further divided them into four different vegetarian groups: semi-vegetarians ate meat but less than once per week; pesco-vegetarians ate fish but avoided other meats; lacto-ovo-vegetarians avoided meat but ate eggs and/or dairy products; and vegans avoided all meats, eggs, and dairy. All vegetarians together had on average a 22% relative reduction in the risk of developing colorectal cancer, compared to non-vegetarians, after carefully adjusting for many other factors. Pesco-vegetarians in particular had a much lower risk compared to non-vegetarians.
Medical Research: What should clinicians and patients take away from your report?
Dr. Orlich: People consuming healthy vegetarian diets may have a lower risk of colorectal cancer than non-vegetarians. Our vegetarians not only ate less meat than the non-vegetarians, but also less sweets, snack foods, refined grains, and caloric beverages and more fruits, vegetables, avocados, whole grains, beans, and nuts. Prior evidence strongly links eating red and processed meat to a higher risk of colorectal cancer and fiber-rich foods to a lower risk.
Medical Research: What recommendations do you have for future research as a result of this study?
Dr. Orlich: We plan to examine the relationship of several specific foods to colorectal cancer risk in our population. Further research into mechanisms linking diet to colorectal cancer is important. Interesting possibilities could include how dietary factors may alter the expression of certain genes or how they may affect the many microbes that inhabit the large intestine and the effects that such changes may have on cancer development. There is also a need for improved methods for accurately measuring long-term diet in large numbers of people.
MedicalResearch.com Interview with: Michael J. Orlich, MD, PhD (2015). Healthy Vegetarian Diet May Reduce Risk of Colon Cancer