Then came the big test.
"We performed two-week food exchanges in subjects from the same populations, where African Americans were fed a high-fiber, low-fat African-style diet and rural Africans a high-fat, low-fiber western-style diet, under close supervision," the researchers wrote.
"In comparison with their usual diets, the food changes resulted in remarkable reciprocal changes," they added. Just two weeks of eating different food changed the types of bacteria living in the colon and what they did.
"This suggests that a move to a fiber rich, low-fat diet may impact the high levels of colon cancer in the African American population," they concluded.