A recent study had a group of African-American volunteers give up their typical diet for two weeks in favor of a high-fiber African diet while a group in Africa did just the opposite. Researchers say the outcome highlights the risks of colon cancer inherent in the typical Western diet.

As 20 U.S. volunteers shifted into a low-fat, high-fiber diet, the same number of volunteers in rural Africa were instructed to eat more junk food.

The result, according to the researchers, was that the Americans experienced less bowel inflammation while the bowel health of the African volunteers deteriorated. The study, although limited, supports the conclusion that the modern Western diet, full of fats and sugars with little fiber, is unhealthy.

"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," said lead researcher Dr. Stephen O'Keefe of the University of Pittsburgh School of Medicine.

While practicing in South Africa, O'Keefe recounted, he noticed that his rural patients rarely suffered from colon cancer or polyps, a known cancer precursor.

In contrast, colon cancer is the second-leading cause of cancer death in the Western world, and it is particularly prevalent in people of African descent in the United States.

In the study, 20 American volunteers and 20 South African volunteers – housed at facilities in their respective countries – spent two weeks on a diet featuring meal ingredients and cooking procedures typical of the alternate group.

A colonoscopy was performed on each of the volunteers at the beginning and end of the study period.

Even in the short period of the study, each group began to display the other's characteristic turnover of cells in the intestinal lining, fiber fermentation levels and signs of bacterial activity and inflammation associated with cancer risk. 

The findings raise concerns that an increasing "Westernization" of diets in Africa could increase the prevalence of colon cancer and turn it into a major health issue, said study co-leader Jeremy Nicholson of Imperial College London.

"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," he says.

O'Keefe added that the reduction in biomarkers linked to cancer seen in the American volunteers suggests "it is likely never too late to modify the risk of colon cancer."

This study was published in the journal Nature Communications.