A fibre rich, low fat diet may help to reduce colon cancer risk in African Americans, reports a study published in Nature Communications. Colon cancer is the second leading cause of cancer death in western society and African Americans show the highest incidence of the disease in the USA.
Stephen O’Keefe and colleagues performed a series of investigations on the importance of diet in the development of colon cancer in a group of 20 African Americans and 20 rural African participants. They found that diets in both populations were fundamentally different, with animal protein and fat intake 2 to 3 times higher in African Americans, and carbohydrate and fibre intake higher in Africans. Colonoscopy results showed greater incidence of colon cancer biomarkers in African Americans.
These differences were also associated with a profound difference in microbiota in both populations. Africans had higher levels of carbohydrate fermenting and butyrate producing bacteria, and African Americans had higher levels of bile acid metabolising bacteria. There is already extensive evidence suggesting an anti-inflammatory and tumour suppressant role for the products of fibre fermentation (particularly butyrate), and evidence suggesting that some products of bile acid metabolism are carcinogenic. These findings may indicate a possible mechanism for dietary mediation of certain colon cancer risk factors.
The authors then conducted a two-week food exchange between the populations, which had a significant impact on colonic microbiota and associated metabolites, resulting in a reduction in cancer risk biomarkers in African Americans, and an increase in rural Africans. This suggests that a move to a fibre rich, low fat diet may impact the high levels of colon cancer in the African American population, however longitudinal studies are necessary to demonstrate this.