Posted on: September 25, 2017 at 2:57 pm
Last updated: November 30, 2017 at 12:15 pm

This article is shared with permission from our friends at Nutrition Facts.

Dr. Dean Ornish showed that a plant-based diet and lifestyle program could apparently reverse the progression of prostate cancer, but that was for early stage, localized watch-and-wait cancer. What about for more advanced stage life-threatening disease?


Below is an approximation of this video’s audio content. To see any graphs, charts, graphics, images, and quotes to which Dr. Greger may be referring, watch the above video.

Dr. Dean Ornish showed that a plant-based diet and lifestyle program could apparently reverse the progression of prostate cancer by making men’s bloodstreams nearly eight times better at suppressing cancer cell growth, But, this was for early-stage, localized, watch-and-wait prostate cancer. What about for more advanced stage life-threatening disease? There had been sporadic case reports in the literature suggestive of benefit. Man, for example, with extensive metastatic disease, given maybe three years to live, goes on a strict plant-based diet. Four years later, it appears the cancer has disappeared. Six years in, he gets a little cocky, and backslides a little bit on the diet. Cancer comes raging back, and he dies. But, that could have been a total coincidence. That’s the problem with case reports, which are kind of glorified anecdotes. You have no idea how representative the outcome is unless it’s formally studied. But throughout the 20th century, all we had were these kinds of case reports—until 2001.

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So, we had all this “preliminary evidence,” based on all the case reports “that prostate cancer may be sensitive to diet even after [it metastasizes].” It may prolong survival, and even cause “remission of bone [metastases] in men with advanced disease.” So, researchers decided to put it to the test “in a 4-month [long] intervention.” They figured too much-saturated fat, too little fiber, and too much meat may be the biggest players in “tumor promotion and progression.” So, they put people on a whole food plant-based diet of whole grains, beans, seeds, and fruit. Figuring this would be quite the “departure from their [regular] diet,” they included a stress-reduction component, in hopes of improving dietary compliance.

Okay. So, who were these ten men? They didn’t just have prostate cancer; they all had “underwent [a] radical prostatectomy” to remove their primary tumor, and then “subsequently had increasing PSA” levels, indicative of probable metastatic disease. PSA stands for prostate-specific antigen; it’s only made by prostate cells, and they just had their entire prostates removed. So, the level should be zero. The fact that they not only still had some PSA, but that it was rising, suggests that the surgery failed, and the cancer had spread and was making a comeback.

Here’s where they started out before the study began. This is a graph of the speed at which each of their PSAs was going up. So, if after four months of eating healthy, the graph looked like this, it would mean the diet had no effect. The cancer would presumably still be powering away, and spreading just as fast as before. Instead, this happened. In two men, it looks like the cancer accelerated—grew even faster. But in the other eight men, the intervention appeared to work, apparently slowing down cancer growth. And, in three, it didn’t just slow or stop, but appeared to reverse and shrink.

Why the different responses? Well, in the Ornish study, the more people complied with the diet and lifestyle recommendations, the better they did. Dietary changes only work if you actually do them. Just because you tell people to start eating a whole food plant-based diet doesn’t mean patients actually do it. One can use fiber intake as a proxy for dietary compliance, since all whole plant foods have fiber, and Ornish’s patients about doubled their fiber intake, from 31 to 59.


How did this group do? They started out even worse, averaging 14 grams a day, and only made it up to 19 grams a day. That’s not a whole food plant-based diet—that doesn’t even make it up to the recommended minimum daily intake. If you look closely, only four men increased their fiber intake at all. So, maybe that may explain the different responses. Like, how did patient 2 do? The man whose fiber improved the most had the best PSA result, and the man whose fiber intake dropped the most had the worst PSA result. Here’s the graph. And, indeed, it appears the more change they made to their diet, the better their results.

The researchers concluded that “a plant-based diet delivered in the context of [stress management]…may slow the rate of tumor progression,” and unlike other treatments, may give patients some control over their disease. And, as Ornish pointed out, “the only side effects are beneficial ones.”

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Health Expert
Dr. Michael Greger is a physician, New York Times bestselling author, and creator of This service provides the first non-commercial, nonprofit, science-based service to provide daily updates on the latest discoveries in nutrition.

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