A Diet for Cancer?

The Dean Ornish solution.

Medically Reviewed by Craig H. Kliger, MD
6 min read

Sept. 25, 2000 -- Imagine knowing that cancer is growing in your body, and you're doing nothing to stop it. A significant number of men with prostate cancer opt for just that -- no surgery, no radiation, just checkups every three months to monitor the tumor.

Because prostate cancer often grows very slowly, and because the standard treatments carry the risk of impotence, incontinence, or both, many physicians endorse this "watchful waiting" approach -- especially for older men. Yet for some patients, it can be extraordinarily difficult to take no action against a cancer they know is inside them.

Dean Ornish, MD, thinks there is something these men can do. Ornish, who startled the medical world several years ago when rigorous trials showed that his combined diet, exercise, and stress-reduction program could reverse heart disease, is now turning his attention to prostate cancer. He and his colleagues are testing the notion that low-tech "lifestyle therapy" can slow, stop, or even reverse the disease in men who are diagnosed early. Could it be that what worked for heart disease can work for cancer, too?

The treatment protocol is based on the heart disease program that Ornish developed at the Preventive Medicine Research Institute in Sausalito, Calif. It calls for 65 men to eat a strict diet -- no meat, oil, or dairy products allowed -- and to engage in various stress-reducing activities including daily meditation, yoga, and exercise. Another 65 men, the control group, will make no lifestyle changes. Both sets of patients will receive prostate-specific antigen (PSA) tests -- an indicator of the cancer's status -- and checkups every three months for a year.

The evidence in support of this approach, according to Ornish, comes mostly from epidemiological research showing remarkable differences in the incidence of prostate cancer in different countries. These studies have found that men all over the world are equally likely to have tiny cancerous lesions -- in essence, the germ of a cancerous growth -- in their prostates. But for men living in countries where the national diet tends to be light on meat and heavy on plant-based foods, these lesions appear less likely to develop into detectable -- and potentially harmful -- masses.

Though nobody knows exactly why this is true, it may be that very early prostate cancers are kept in check by a plant-based diet -- or that something about the typical Western diet encourages microscopic lesions to become tumors. Studies in mice, Ornish says, have also shown that prostate tumors grew far more slowly -- and in some cases even regressed -- when the animals ate a diet low in fat.

Further support for this idea came in a study published in the July 2000 issue of the British Journal of Cancer. Researchers at the Imperial Cancer Fund in Oxford, England, found that men who eat a vegan diet have lower levels of a protein known as IGF-1. This protein's role in prostate cancer isn't fully understood, but the researchers say that, as with PSA, high levels of it are often found in men with the disease.

And though there is little research suggesting that exercise or stress management will affect prostate cancer, there is some data suggesting that these lifestyle changes can have a positive impact on other types of cancer. In a study published May 1, 1997, in the New England Journal of Medicine, researchers found that women who were more physically active were less likely to develop breast cancer than were less-active women.

For Ornish colleague Peter Carroll, MD, a urologist at the University of California, San Francisco, the evidence was enough to convince him that this approach was worthy of more thorough study. "This is a group of men who are at low risk because their cancers grow slowly, if at all," he says. "If lifestyle changes can make a difference -- particularly given the other benefits of such changes -- then we would have another treatment option for a substantial number of men."

In fact, as many as 10% to 15% of all men diagnosed with prostate cancer might be candidates for this approach, according to Carroll. This size of this group has convinced the U.S. Army to participate in a larger clinical trial with as many as 3,000 men, which should start this fall. "Given the data, I think that lifestyle changes hold a good deal of promise for the treatment of prostate cancer," said Colonel Judd Moul, MD, director of the Department of Defense's Center for Prostate Disease Research.

It's hard to find a prostate cancer expert who will criticize the notion of a lifestyle-induced remission. Consensus seems to hold that the epidemiological evidence amounts to a good reason to test this hypothesis, and that Ornish and his colleagues, by setting up a randomized, controlled trial, are taking the right course to validate the theory.

Still, not all urologists are as enthusiastic as Moul and Carroll. Some take issue with watchful waiting itself. William Catalona, MD, professor of surgery at Washington University in St. Louis and a leading prostate cancer expert, believes that this approach is really nothing more than a delaying tactic based on outdated information. "About five years ago there was data coming out of Sweden suggesting that watchful waiting was as good as surgery, particularly in older men with early-stage cancer," he says. But, Catalona adds, "We haven't seen any follow-up since then. I think watchful waiting causes some men to postpone effective therapy so long as to miss their window of opportunity for successful treatment."

But the major criticism is the same one as for Ornish's anti-heart-disease regimen: that the program is too draconian. "The dietary change is much too difficult for all but the most committed person to stick to," says Catalona. Both Ornish and Moul, not surprisingly, disagree. When threatened with cancer, they say, people become motivated to make changes that might otherwise have seemed unthinkable.

That was the case for Dennis Simkin, a San Francisco Bay area resident who learned three years ago, at 51, that his PSA measurement of 6.8 was in the borderline danger range. A biopsy ordered by his doctor, Carroll, confirmed that he had early-stage prostate cancer. Simkin opted to try the Ornish program in hopes of avoiding the need for treatment that might make him impotent, incontinent, or both.

"We had always eaten fairly healthy," Simkin says, "But this was drastic. It did take time to adjust. Eliminating all added oil from our diet, for instance, was hard."

Still, soon after making the changes, Simkin noticed that he felt better. "That made the transition much easier," he says. What's more, his PSA quickly dropped below 4.

But Catalona is not convinced that Simkin's results will be that meaningful when the final data are tallied at study's end. "As far as diet and lifestyle changes go, I think that there's a good chance they will slow the progression of the disease and patients will see a drop in PSA, but that benefit will only be temporary," he says. The dietary changes might deprive the tumors of some nutrients they need to grow, he says. But tumors are adaptable, and it's his hunch that the cancer cells will find another way to get the nourishment they require.

That may be what is happening to Simkin. His PSA level has slowly risen back over 6. "We're watching it very closely now," he said, "and it may end up that I have to have surgery or radiation after all."

Joe Alper is managing editor of DoubleTwist.com's online magazine about biotechnology and cutting edge biomedical science.