High colon cancer risk caused by Western junk food can be reversed with healthy, high-fiber diets, study proves

(NaturalNews) Switching from a Western diet high in meat and fat to a diet rich in vegetables and beans may reduce a person's risk of colon cancer in just two weeks, according to a study conducted by researchers from the University of Pittsburgh and Imperial College London and published in the journal Nature Communications. Colon is the second most common cause of cancer death in wealthy countries.

The study took urban, African American residents of Pittsburgh and compared their colon cancer risk and diets with that of rural, South African villagers. The researchers then had the two groups swap diets for two weeks, with shocking results.

Different diets lead to different gut microbes

Previous studies have shown a strong link between diet and colon cancer, with meat (especially red and processed meat) increasing the risk and fiber decreasing it. The researchers hypothesized that differences in diet are a main reason that the risk of colon cancer is 100 times higher among African Americans than among residents of rural regions of Africa.

The researchers recruited 20 African Americans from Pittsburgh and 20 rural residents of KwaZulu-Natal, South Africa. Upon analyzing the diets of the two groups, they found that the African Americans consumed much less fiber than the South Africans, but ate two to three times as much fat and animal protein.

When they sampled the gut microbes of the two groups, they found that the African Americans had much higher levels of microbes that break down bile acids (produced by the body to help digest fatty food), while the South Africans had much higher levels of microbes that help break down carbohydrates and that produce the chemical butyrate (which has been shown to lower cancer risk).

Colonoscopies revealed polyps in the colons of nine of the 20 African Americans, and not a single polyp in the South Africans. Polyps are believed to be a risk factor for colon cancer, as they can sometimes develop into malignant tumors.

Changes are "startling," "astonishing"

The researchers then brought the participants in to local centers and fed them controlled diets for two weeks. The African Americans were fed a traditional rural South African diet, consisting of high-fiber foods such as bean soup, corn fritters, fish tacos and raw mango. The South Africans were fed a high-fat, high-protein, low-fiber Western diet with foods such as burgers, fries, hash browns and sausages.

At the end of the intervention, inflammation and other biological markers for colon cancer had significantly decreased in the African Americans, while markers of cancer risk increased in the South Africans.

"We were astounded at the degree of change," lead researcher Stephen O'Keefe said. "We thought we'd find a few changes here and there when they swapped diets, but this mirror image was totally unexpected."

The researchers also found that in the course of two weeks, the gut microbes of the participants had undergone dramatic changes to accommodate the new diets. In the African Americans, this led a 2.5-fold increase in butyrate levels, which might be responsible for some of the reduction in cancer risk markers. In contrast, butyrate levels among the South Africans decreased by 50 percent. Likewise, the South Africans suffered an increase in bile-producing microbes.

Scientists have remained uncertain how dietary fiber, which reaches the colon undigested, can influence cancer risk. The new study suggests it may do so, in part, by changing the gut microbiome.

"What is startling to me is how profoundly the microbes, metabolism and cancer risk factors change in just two weeks of diet change," senior co-author Jeremy Nicholson said. "It means to me that diet and environment and microbial genes are likely to be much more important than individual human genes in determining individual colonic cancer risks."

(Natural News Science)

Sources:

http://www.theguardian.com

http://www.nature.com

http://www.reuters.com