It is known that consuming a diet high in red meat is a risk factor for developing colon cancer. Now we have a report that specifically demonstrates that a vegetarian diet is associated with a reduced risk of developing colorectal cancer.
A report this month in the journal JAMA Internal Medicine demonstrated that vegetarians compared to meat-eating nonvegetarians have a lower risk of developing colorectal cancer. Moreover, those vegetarians that also consumed fish had even lower rates of colorectal cancer. Researchers from Loma Linda University School of Public Health recruited 77,659 men and women from Seventh-day Adventist churches throughout the U.S. Diet was assessed at baseline and categorized into four vegetarian dietary patterns and a nonvegetarian dietary pattern. The four vegetarian dietary patterns were vegan, lacto-ovo vegetarian, pescovegetarian, and semivegetarian. All enrollees filled out questionnaires that included over 200 food items. During an average of seven years of follow-up, the researchers found 380 cases of colon cancer and 110 cases of rectal cancer. Vegetarians had a 21 percent reduced risk compared with nonvegetarians. Interestingly, some vegetarian diets were better than others. Results for participants who modified a vegetarian diet with eating meat or fish up to four times a month demonstrated little benefit. However, “pescovegetarians,” who ate fish one or more times a month and other meats less than once a month reduced their risk by 42 percent compared with nonvegetarians.
It is felt that phytochemicals from fruits, vegetables, and whole grains offer chemoprevention of colorectal cancer. An example of a phytochemical is curcumin from turmeric. Curcumin is consumed throughout Southern Asia where the incidence of colorectal cancer is very low compared to westernized nations. Western diets contain refined grains, animal proteins, saturated fats, and are low in fruits and vegetables. The digestion by-products of a western diet that reach the colon contain pro-inflammatory molecules and carcinogens. Indeed, countries that have been moving to a western diet, including Southern Europe and Japan, have seen increasing rates of colorectal cancer.
It is likely that our gut microflora have adapted to non-digestible phytochemicals which are metabolized into final products that are anti-inflammatory and chemopreventative. A western diet alters the amount of phytochemicals reaching the gut and also alters the gut microflora. These changes likely contribute to the higher rates of colorectal cancer along with obesity and the metabolic syndrome that are prevalent in western societies.
We should strongly encourage a diet high in fruits and vegetables along with the consumption of fish. I would recommend a daily serving of at least 2 cups of fruit along with 2-1/2 cups of vegetables. You should try to consume 20-35 grams of fiber per day. See our fiber guide to help you calculate your daily intake of fiber. With this recent report from JAMA Internal Medicine, it makes sense to eat fish one or more times per month.
Here’s to your colon health!
Frank Farrell, MD, MPH, AGAF