Healthy Diet & Exercise Program Inhibits Growth of Prostate Cancer Cells

By Jeff Novick, M.S., R.D., L.D./N.

To help prevent prostate cancer American men would be better off if they adopted a low-fat, high-fiber diet and started exercising regularly, suggests a new study just published in The Journal of Urology (2001: 166: 1185-1189).

The results, reported by lead researcher James Barnard, Ph.D., UCLA Department of Physiological Science, suggest that an active lifestyle and a diet rich in fruits, vegetables, and whole grains could reduce the growth of prostate cancer cells by as much as 45%. In the study, Dr. Barnard and colleagues obtained blood samples from 13 overweight men, ages 42 to 73, on the first day of a two-week program of diet (rich in fruits, vegetables, and whole grains) and exercise. The samples were transported to a laboratory at UCLA where they were placed in dishes with prostate cancer cells. The investigators then measured the rate of tumor cell growth. It was rapid.

Eleven days later, close to the conclusion of the men’s program, the scientists obtained a second set of blood samples. Once again, they deposited the samples in dishes containing prostate cancer cells. Compared to the “entry” blood samples of the men, these “exit” blood samples showed a 30% decrease in the rate of tumor cell growth. “The results are very exciting,” notes Dr. Barnard, “because they suggest that with changes in lifestyle we can dramatically reduce prostate tumor cell growth.”

To answer criticism that the slow-down in prostate cancer growth may be transient, an effect merely of 11 days of intensive diet and exercise that won’t last, the scientists obtained another set of blood samples from eight men, ages 38 to 74, who had been followers of of a healthy, high-fiber, low-fat, plant-based diet for an average of 14 years. Compared to the samples of the overweight men on their first day of the healthy diet, the samples of the eight long-term healthy eating followers showed a 45% reduction in the growth of prostate tumor cells.

The precise factors responsible for the reduced growth rate are yet to be determined. “We do know, though, that testosterone, estradiol, and insulin stimulate tumor growth, so if you decrease your levels of these three hormones, as you do with a high-fiber, low-fat, plant-based diet, there’s an excellent chance you’re stunting tumor growth,” states Dr. Barnard. Though this new study is preliminary and involves only laboratory work with test tubes, it echoes a large body of research indicating that lifestyle plays a pivotal role in the prevention of invasive prostate cancer. Death rates from prostate cancer are highest in countries like the United States where the typical diet is full of fatty foods, particularly animal fats like red meat and fatty dairy foods, and lacking in natural, fiber-rich foods such as fruits, vegetables, and whole grains. Among American men, cancer of the prostate is the leading cause of death due to cancer in men who don’t smoke. Indeed, in the U.S., prostate cancer kills nearly as many men as breast cancer kills women.

By contrast, in Asian countries like China, Korea, and Japan, where most people still follow traditional diets high in fiber and low in fat, rates of prostate cancer are among the lowest in the world. In these countries, prostate cancer is 7 to 15 times less common than in the United States. In the rural county of Qidong, China, the incidence of invasive prostate cancer is less than 1 case per 100,000 men. In America, there are 102 cases for every 100,000 men – more than 100 times as many victims!

Yes, heredity may play a role. The more family members who have prostate cancer, the greater a man’s personal risk. Yet heredity or race appears minor compared to lifestyle. Carefully-done studies of native-born Japanese men who migrated to America found that when these men retained their traditional diet while living in the U.S., their rates of invasive prostate cancer remained low. If, however, they adopted the high-fat, low-fiber diet and sedentary lifestyle of America, their prostate cancer rates soared to those of men born and bred in the States - and in just one generation’s time. Scientists estimate that lifestyle factors like diet and exercise account for more than 75% of advanced prostate cancer cases. Interestingly, it’s not as if men in China, Korea, and Japan don’t have prostate cancer. They do. Autopsy studies of older men throughout the world, including men from Asian countries, have found tiny, microscopic clusters of cancer cells inside the prostate. The tiny clusters, researchers now believe, are a natural part of the aging physiology of healthy males.

What separates Asian men from American men is what happens to those microscopic cancer cells. In Asian men, they tend to stay within the prostate gland, causing no clinical problems whatsoever. Rarely do they penetrate past the gland, destroying the body’s organs. Unfortunately, that’s not the case in Western, fat-rich nations like the U.S. Here, tiny clusters of cancer cells inside the prostate don’t seem to want to stay inside – or stay tiny. They tend to be much more aggressive, breaking out of the gland, multiplying, and wreaking havoc. Men living in America have about seven times the risk of developing advanced, life-threatening cancer as do men living in Korea. “I’ve prepared a new slide for my lecture on prostate cancer,” says Dr. Barnard. “The headline is: American men die from prostate cancer. Asian men die with prostate cancer.”

If, as Dr. Barnard’s new research suggests, tumor cell growth can be inhibited, there’s new hope for American men. New power. Through lifestyle changes including a high-fiber, low-fat, plant-based diet, we might, like Asian men, be able to arrest the development of prostate cancer cells. Very likely, regular exercise combined with a low-fat, high-fiber diet can help keep cancer cells within the prostate – quiescent, silent – far less likely to break out into aggressive, invasive forms.

What may be critical, too, is making lifestyle changes early – before the cancer is out of control. The blood samples of the healthy diet participants were effective at stunting the growth of tumors, Dr. Barnard suspects, because the cancer cells used in the initial part of the study were in the beginning stages of ma-lignancy: they were androgen-depen-dent, meaning they needed high levels of hormones like testosterone to fuel their growth. With- out these hormones, or with diminished levels, as was the case with the healthy diet blood serum samples, cell growth slowed. But when Dr. Barnard and his team added these same blood serum samples to cancer cells that had progressed to a more advanced stage of malignancy, they had no effect in halting tumor growth. At this second, more virulent stage, cancer cells are androgen-independent. They don’t need hormones to fuel their growth. They multiply rapidly, voraciously, all on their own.

“Keep in mind, though, that when prostate cancer is in its early stages, we do seem to have some control over it, and that’s tremendously encouraging,” affirms Dr. Barnard. “There’s every reason to believe that if you catch this stuff early on – by adopting a healthy lifestyle and maintaining a high-fiber, low-fat, plant-based diet – you can block its growth. You can significantly increase the odds of living your life free of invasive prostate cancer.”