Diet Effects Colon Cancer Risk

Diets with more animal protein and less soluble fiber increases cancer risk.

The risk of colon cancer was found to be directly affected by the type of food an individual consumes, according to a recent study.

Published online in Nature Communications, the study found that African Americans and Africans who swapped their typical diets for 2 weeks saw their respective risks of colon cancer exchanged as well, as reflected by altered gut bacteria. The study noted that colon cancer is the second leading cause of cancer death, with African Americans carrying the greatest disease burden in the United States.

"The African American diet, which contains more animal protein and fat, and less soluble fiber than the African diet, is thought to increase colon cancer risk," principal investigator Stephen O'Keefe, MD, said in a press release. "Other studies with Japanese migrants to Hawaii have shown that it takes only one generation of Westernization to change their low incidence of colon cancer to the high rates observed in native Hawaiians. In this project, we examined the impact of a brief diet change on the colon in a controlled setting where we didn't have to worry about the influence of smoking and other environmental factors on cancer risk."

The study assessed the in-home diets for 20 African American and 20 rural South African individuals between the ages of 50 to 65 years. The participants ate meals prepared by researchers with ingredients and cooking techniques typical of the other group.

The researchers evaluated fecal and colon content samples obtained from a colonoscopy from each participant at baseline and after the 2-week study.

Despite the brief timeframe for the study, each group experienced the other side’s rate for turnover of intestinal lining cells, fiber fermentation levels, and markers of both bacterial metabolic activity and inflammation associated with cancer risk.

Additionally, African Americans were found to have increased butyrate production, which is believed to play a vital role in anti-cancer pathways. The researchers removed intestinal polyps from 9 African American participants, while there were none found in the Africans.

"We can't definitively tell from these measurements that the change in their diet would have led to more cancer in the African group or less in the American group, but there is good evidence from other studies that the changes we observed are signs of cancer risk," said co-author Jeremy Nicholson, PhD, in a press release.

The study found that increasing the amount of fiber in the diet from approximately 10 grams to more than 50 grams in African Americans caused biomarker changes that indicate a reduced cancer risk, while eating less animal fat and proteins may also be beneficial.

"These findings are really very good news," Dr. O'Keefe said. "In just two weeks, a change in diet from a Westernized composition to a traditional African high-fiber, low-fat diet reduced these biomarkers of cancer risk, indicating that it is likely never too late to modify the risk of colon cancer."