The cells in certain cancers, like breast cancer and colon cancer, have been shown in labs to start with a high level of genetic instability and then in later stages this level goes down

In addition to setting the stage for the development of colon cancer, scientists have now found that a diet high in red meat and processed foods can lead to relapse or death in colon cancer patients who are undergoing treatment.

Researcher Jeffrey Meyerhardt of the Dana-Farber Cancer Institute in Boston, Massachusetts and colleagues looked at the impact of two distinct diet patterns, one healthy and one not, in a group of one-thousand patients with stage-three colon cancer, cancer that has spread to the lymph nodes.

The patients were part of a clinical trial of people receiving chemotherapy in the six months after surgery, and they kept detailed diaries of what they ate during this time.  Those who reported eating a healthy diet consumed large amounts of fruits, vegetables, poultry, and fish.  Those who ate the so-called Western-style diet frequently consumed red meat, fat, refined grains and dessert.

Five years later, 324 patients had a recurrence of cancer and 223 patients had died.  Investigators found that those in the Western group with the worst diet were three times more likely to have a recurrence and die of colon cancer than those in the Western group who ate less junk food.

"People who have a higher Western pattern diet have an increased risk for recurrence, but that does not mean people who have very little of a Western pattern diet have no chance for recurrence," Meyerhardt said. "It is just relatively, it is an additional thing to improve people with colon cancer's outcomes."

In contrast, among those patients who ate a healthy diet, there was no increased risk of recurrence and death.  

Meyerhardt says the study makes clear what the culprit is:

"It is not really increasing the amount of fruits and vegetables, but really trying to reduce the amount of red meat intake and fatty foods and sugary, 'desserty' foods...," Meyerhardt said. "

The study on diet and colon cancer is published this week in the Journal of the American Medical Association.