Diet, Exercise and Reduced Stress Slow Prostate Cancer, Study Finds

When the study began and then a year later, the researchers gave both groups of men the prostate-specific antigen (PSA) blood test, which is widely used to monitor the progression of the cancer. Those on the diet and exercise regimen saw their PSA levels drop by an average of 4 percent, while those in the other group saw theirs rise an average of 6 percent, the researchers found.

In addition, blood from the men in the diet and exercise group appeared to inhibit prostate cancer cells in laboratory tests, indicating that something in their diet or their bodies' response to the regimen was inhibiting their cancer, Ornish said.

Moreover, none of those who made the lifestyle changes needed any cancer treatment during the study period, whereas six of those in the other group did.

"This is the first randomized trial showing that the progression of prostate cancer can be stopped or perhaps even reversed by changing diet and lifestyle alone," said Ornish, who stressed that the changes should be considered only as an addition to standard treatment and not a substitute.

Two recent studies found that breast cancer patients who ate low-fat diets and exercised regularly were less likely to suffer recurrences, Ornish noted. "We think we may be able to give many people new hope and new choices that they didn't have before," he said.

Other researchers were cautious, saying the study had not yet demonstrated that the lifestyle changes help people live longer, and it was difficult to pinpoint which aspects of the regimen might be beneficial.

"So many variables were changed in the experimental group that it is not possible to sort out which of the many lifestyle factors . . . or combination thereof, was responsible for the observed effects," Howard L. Parnes of the National Cancer Institute wrote in an e-mail.

In addition, the changes were so dramatic that it is unclear how many men could sustain them, Parnes said. "Although the findings appear to support the hypothesis that dietary and lifestyle factors can potentially alter the natural history of prostate cancer, there are many caveats."

In comments accompanying the article, Paul H. Lange of the University of Washington said the study would likely trigger follow-up research.

"Even if scientific evidence is still meager, complementary medicine approaches have strong appeal in practicing the medical art since they give the patient an active role in his care and promote an attitude of optimism and hope," he wrote.