Today, we look at how a plant-based lifestyle is put to the test against early- and late-stage cancer.
Higher consumption of a healthy plant-based diet was significantly associated with a lower chance of having an elevated PSA, which can be a sign of prostate cancer. We’re talking about potentially cutting the odds of having an elevated PSA in half with diet. The researchers concluded: “This study provides strong evidence supporting the potential use of plant-based foods in the prevention and treatment of prostate cancer.”
Not so fast, replied an editor of the journal. This paper certainly doesn’t present final, convincing proof that reduced PSA levels due to a plant-based diet in fact translate into what we actually care about: less prostate cancer. Harvard cohort researchers took up the mantle to answer that question. And indeed, greater consumption of a healthful plant-based diet does appear to reduce the risk of getting prostate cancer and dying from prostate cancer by nearly half for men under age 65.
And those adhering more to a healthy plant-based diet who do get cancer had 90% lower odds of ending up with high-grade, more severe prostate cancer, and appeared to be better able to handle cancer treatment, and ended up with better sexual function, less incontinence, and more vitality.
This is consistent with the role of diet and nutrition in the prevention and treatment of cancer more generally, where the evidence points to a diet with minimal animal products. What if you already have cancer though? Study findings suggest that adhering to plant-based diets may be beneficial for overall cancer survival and may potentially improve the prognosis for common cancers such as breast, colorectal, and prostate cancers.
It starts with case reports like this. A 73-year-old man with prostate cancer was placed on a plant-based diet, and within 10 days, his tumor markers were down about 75%. But case reports are like glorified anecdotes. You can’t know if a healthier diet and lifestyle actually help until you run a randomized, controlled trial and put it to the test,
Dr. Dean Ornish, famous for showing the progression of heart disease could be reversed, opening up arteries without drugs, without surgery, just a plant-based diet and lifestyle program, eliminating angina chest pain in about three-quarters of patients within a matter of months. He decided to move from killer #1—heart disease—to killer # 2—cancer. Ninety-three men with early-stage watch-and-wait prostate cancer were randomized to either standard care or a plant-based diet along with walking and relaxation.
The cancer tended to get worse in the control group, but comparatively better in the plant-based group. When blood from the patients on the standard diet was dripped onto prostate cancer cells growing in a petri dish, cancer cell growth rates were cut by 9&. Their bodies were doing the best they could to beat back the cancer. The blood of patients on the plant-based program, though, knocked down the cancer growth by 70%. Even living more healthfully made their bloodstream almost eight times less hospitable to cancer. This was after a year. Subsequent studies have shown that you can see a significant cancer-fighting effect after less than two weeks on a similar Pritikin-style plant-based diet with exercise.
Ornish took biopsies from the prostate cancer patients before and after three months, and saw a significant change in the expression of more than 500 genes. Of course, what we really care about are disease outcomes. By the two-year follow-up, significantly more men in the control group had enough cancer progression that they had to go into treatment. For example, five had to get radical prostatectomies, which can lead to urinary incontinence and impotence in 60%, whereas none of the men in the lifestyle group was forced to go into surgery.
What about those with more serious disease? Researchers followed 10 patients with recurrent prostate cancer, meaning those whose invasive cancer had to be cut or burned out with radiation, yet their PSA levels started to rise again, signaling the cancer was back. There was no control group per se in this study. Each patient was kind of their own control before and after, being asked to center their diets around more whole plant foods. There was a significant decrease in the rate of PSA rise, suggesting a slowing of cancer growth. Four out of 10 patients actually saw their PSA levels go down, suggesting the possibility of at least some degree of disease remission. And nine out of 10 had a reduction in their rates of PSA rise, as well as an improvement of their PSA doubling times, which is a proxy for how fast the tumor doubles in size. The increase in average doubling time went from about 12 months before the dietary change to 112 months, which is the largest that has been ever reported in any kind of dietary intervention trial for recurrent prostate cancer.
What about really advanced cancer, stage four with spread to distant organs? Out of nine patients willing to go on a plant-based macrobiotic diet, three men experienced long-term regression of multiple bone lesions, compared to no regression or healing in nine matched control subjects who continued eating the standard American diet. Those on the healthier diet went on to live an average of 19 years more, compared to those with the same severity of cancer not even living for 4 years more, on average, on their standard diet. Now this was not a randomized study, so maybe it says something about those willing to eat healthfully rather than healthful eating itself. But what’s the downside? As Dr. Ornish likes to say, the only side effects are good ones. A large number of patients with metastatic prostate cancer, for example, die not from their cancer, but rather from non-cancer causes, and the number one cause is heart disease; so, a heart-healthy diet could only help.
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.
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 all 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.
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. 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.”
Finally today, we look at what happens when metastatic prostate cancer patients were taught to increase intake of whole grains, vegetables, fruits, and beans, and to decrease consumption of meat, dairy, and junk?
Dr. Ornish and colleagues were able to show an apparent reversal in the progression of early stage localized prostate cancer with a plant-based diet and lifestyle program, and researchers at the University of Massachusetts and elsewhere showed a similar diet may help slow the progression of even advanced prostate cancer over a period of four months. How about six months? Researchers at UC San Diego found more cancer patients in the same situation and put them through the same protocol. These were patients who were already treated for “invasive prostate cancer…by [either] radical prostatectomy or radiation therapy,” yet had “rising PSA” levels, suggesting the treatment didn’t work, and the cancer was on the move.
In those with a cancer recurrence, PSA levels typically “rise exponentially…, reflecting the gradual, inexorable growth of the cancer in the body.” “[T]he rate of [this] PSA rise is the single best predictor of…the…development of overt metastatic disease, as well as of overall survival.” The next step would be what’s called “hormonal therapy,” which is chemical or surgical castration, which has a list of side effects, including loss of libido and sexual function, and strength, and vitality. Therefore, we try to hold off on that for as long as possible. So, if we’re just waiting, might as well give diet a try.
So, “[t]hey were taught to increase intake of whole grains, vegetables, fruit, and [beans], and to decrease meat, dairy, and refined [carbs].” Of all possible lifestyle interventions, why a whole food, plant-based diet? Well, if you look around the world, there are huge differences in prostate cancer rates, with “We’re #1, USA, USA” rates up to a hundred times higher than some places in Asia, for example. And, it’s not just genetic; within one generation of coming to the U.S., cancer rates shoot up, and the grandkids end up with the same top-of-the-pile rates. A whole range of “lifestyle factors” have been looked at, but diet appears to have the greatest influence. Specifically, “[c]onsumption of meat and dairy…appears to increase risk, and consumption of plant…foods appears to decrease risk.” Hence, the plant-based diet.
“A possible mechanism…is arachidonic acid,” an inflammatory compound which we make from omega-6 rich oils, like corn oil, sunflower, safflower, and cottonseed oil, and also comes “preformed in…animal-based foods”—particularly from chicken in the American diet, and also eggs. And, in a petri dish, at least, arachidonic acid appears to stimulate prostate cancer cell growth as much 200%. But, ask men to remove processed and animal foods from their diet for six months, and what happens?
Nine of the ten patients showed an apparent slowing of cancer growth, and four of the nine an apparent reversal in cancer growth. The average “doubling time”—an estimate of how long it takes for their cancer to double in size—slowed from doubling every year, to closer to every ten years.
There’s been other studies using various diets and nutritional interventions, like vitamin supplements, but none have worked as well as this one. And, their compliance wasn’t even all that great. They did good about boosting their whole grain consumption, especially in those first three months, but then backslid a bit. They did eat more vegetables, including a serving of greens, and an extra serving of fruit—at least early on—and at least ate one whole serving of legumes a day, when they started. So, the researchers “did observe some [dietary] recidivism by” the end of the study. The patients started out stronger, but then started to slide back into old habits.
So, the researchers checked to see if maybe they were better able to beat off the disease during that early period, and indeed, at the end of three months, on average, there was PSA reversal. So, “[c]hanges in the rate of [PSA] rise” were like “opposite” that of whole food plant intake, “raising the provocative possibility that PSA may have [been like tracking those changes,] suggesting that [the] adoption of a plant-based diet may have therapeutic potential in the management of [recurrent prostate cancer].”
Their “findings suggest” that without further surgery, radiation, or chemo, “disease progression” can be slowed, or even reversed, despite the “prevailing scientific consensus…that cancer progression is largely irreversible.” They’re “not refut[ing] the benefits of standard therapies,” and not “guarantee[ing] that a plant-based diet and stress reduction will always induce remission. But [the results] do contribute to [this] growing [medical] literature that…in at least some circumstances, cancer may be partly reversible.” Just by modifying “dietary and lifestyle factors”, men “may be able to prevent disease spread”—all without getting their testicles chopped off.
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