African-Americans and rural South Africans swapped diets for
two weeks, they also swapped risk factors for colon cancer.
And the surprise is that it happened so quickly.
involved 20 African-Americans who ate South African fare
including cornmeal and beans for two weeks, while 20 South
Africans consumed an American diet full of meat protein and
fats, including fast-food burgers and chicken. The South
African diet consisted of one-sixth the meat of the American
University of Pittsburgh-based study published online in
Nature Communications found that the South African
cornmeal-bean diet reduced risk factors for colon cancer,
including changes in gut flora and reductions in inflammation
in colon’s mucosa in the American group, while the American
diet notably increased the Africans’ risk factors for colon
study, involving an international research team, confirms that
dietary fiber alone reduces inflammation and blocks secondary
bile in the colon, cutting the cancer risk. The South African
diet reduced levels of secondary bile in the colon by 70
same carcinogenic bile increased in South Africans on the
American diet by 400 percent, the study found.
plant-based, high-fiber African diet also elevated levels of
butyrate, a molecule that reduces inflammation levels and
you can increase the amount of (butyrate), you can override
the carcinogenic effects of fat and meat," said lead
author Stephen J.D. O’Keefe, a physician in the Division of
Gastroenterology, Hepatology and Nutrition in Pitt’s School
plant-based South African diet is considered a factor in that
nation’s colon-cancer rate of only five people per 100,000
population, as compared with the African-American colon cancer
rate of 65 per 100,000 — a rate 13 times greater among
participants were provided food in measured quantities and
received biopsies of colon mucosa before and after the study.
Each of the 40 participants also underwent colonoscopies, with
regular testing for healthful and colon-cancer biomarkers in
the urine and feces.
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
study didn’t last long enough to produce changes in
cholesterol and blood pressure, he said.
such studies won’t likely change eating habits, "our
best hope is that it will open eyes to other possibilities,
and point to the fact that a high-fiber diet is not difficult
to follow and is well tolerated," Dr. O’Keefe said.
"It is enjoyable to eat good food."
Greger of NutritionFacts.org said "studies like this show
that diet can trump genes when it comes to some of our most
Kahn, a clinical professor of medicine at the Wayne State
University School of Medicine in Detroit, said the study
represents "sophisticated science."
have learned that changes in dietary patterns have profound
influences that occur very quickly," he said, citing two
other studies that used plant-based diets to reduce angina
within two weeks and lead to prostate-cancer suppression in
think the message here is that this is further evidence that
food is information and food speaks directly to genes about
the risks of diabetes, heart disease, cancer and obesity, and
it doesn’t take long to do this," Dr. Kahn said.