Scientists have found dramatic effects on risk factors for colon cancer when American and African volunteers swapped diets for just two weeks.
Colon cancer is the fourth most common cause of death from cancer worldwide. It accounts for over 600,000 deaths annually. Colon cancer rates tend to be much higher in the west than in Africa or the East. However, African Americans tend to shoulder a majority of the disease’s burden.
Western diets are high in protein and fat but low in fiber. These diets are thought to raise colon cancer risk compared with African diets high in fiber and low in fat and protein.
A new study confirms that a high fiber diet can substantially reduce risk. The study also shows that bacteria living in the gut play an important role in this effect.
The study was published in Nature Communications on April 30th.
In order to investigate the possible roles of diet and gut bacteria, researchers carried out a study with a group of 20 African American volunteers and another group of 20 participants from rural South Africa.
The two groups swapped diets under tightly controlled conditions for two weeks.
The volunteers had colonoscopy examinations before and after the diet swap. The patients’ biological markers were then measured taken from samples of bacteria taken from the colon. Biological markers indicate colon cancer risk.
At the beginning of the study, when the groups had been eating their normal diets, almost half of the American subjects had polyps. Polyps are abnormal growths in the bowel lining that may be harmless but can progress to cancer. None of the participants from rural South Africa had these abnormalities.
After two weeks of the swapped diets, the American group had significantly less inflammation in the colon and reduced biomarkers of cancer risk. In the rural South African group, measurements indicating cancer risk dramatically increased after two weeks on the western diet.