LOS ANGELES, Jan. 14 -- UCLA scientists report that 11 days of daily exercise and a low-fat, high-fiber diet induce prostate cancer cells to die.
The research, published in the new issue of the journal Cancer Causes and Control, is the first to show that diet and exercise can kill prostate cancer cells.
"You can make changes in a short period of time that have a dramatic impact on your health - in this case, on the growth and death of prostate tumor cells," said R. James Barnard, professor of physiological science at UCLA and lead investigator on the study.
Barnard and his UCLA colleagues studied two groups of men: 14 obese men, ages 42 to 73, without prostate cancer, who participated in an 11-day diet and exercise program at the Pritikin Longevity Center; and 8 men, ages 38 to 74, who have exercised regularly and followed a low-fat, high-fiber diet for more than 14 years.
The researchers - who also include Tung Ngo and Christopher Tymchuk, UCLA graduate students working in Barnard's laboratory; Pinchas Cohen, a researcher at UCLA's Jonsson Cancer Center and professor of pediatrics at UCLA's David Geffen School of Medicine; and William Aronson, a researcher at UCLA's Jonsson Cancer Center and an associate clinical professor in the Department of Urology at UCLA's David Geffen School of Medicine - collected blood serum samples from the 14 men before they began the 11-day Pritikin program. At UCLA, the researchers mixed these serum samples in dishes with prostate cancer cells. At the end of the 11-day program, the researchers collected a second set of blood serum samples from the same 14 men, and placed these samples in laboratory dishes with prostate cancer cells.
Prostate cancer cell death Among the 14 men at the beginning of their diet and exercise program, fewer than three percent of the LNCaP cells - prostate cancer cells - in the cell culture showed apoptosis (programmed cell death). At the conclusion of the 11-day program, more than 40 percent of these cells were on their way to death, and in the 14-year group of eight men, more than 50 percent of these cells were on their way to apoptosis, or death.
"That was the finding that made our jaws drop," Barnard said. "We don't know yet whether these dramatic changes that occurred to prostate cancer cells cultured in a laboratory will also occur in patients; we have hope that these changes will occur."
In an attempt to understand what might be inducing the apoptosis of the tumor cells, the scientists measured blood serum levels of a hormone called IGF-I, which stimulates tumor cells to grow; a high level of IGF-I is a risk factor for prostate cancer, Barnard said.
At the end of the 11 days, IGF-I levels for the 14 men had decreased by 20 percent. The eight men who had followed the diet and exercise program for 14 years had IGF-I levels 55 percent lower than the 14 men had at the start of their diet and exercise program.
"Insulin is the primary factor that stimulates the liver to produce IGF-I," Barnard said. "In previous research, we have shown that diet and exercise lower the serum insulin level; we suspected that diet and exercise should lower the IGF-I level as well, and we have found that to be true."
While IGF-I floats in the bloodstream, it binds to a protein, IGFBP-I, which limits the amount of IGF-I that is available to interact with tissue. Higher levels of this binding protein are desirable, causing a drop in free IGF-I levels, Barnard said.
Over the 11-day program, IGFBP-I levels increased by 53 percent, while in the long-term group of eight men, IGFBP-I levels were 150 percent higher than the short-term group had at the outset of the program.
"We didn't expect the results would be this dramatic," Barnard said. "We found dramatic changes in both IGF-I and IGFBP-I levels with diet and exercise. The important message is you can change your levels of both IGF-I and IGFBP-I in a very short period of time, and that may have an important impact on your prostate health."
Implications of the research
"I've been telling people for years if they want to avoid most of the health problems we have in this country, they should go on a low-fat, high-fiber diet and do about an hour of aerobic exercise every day," Barnard said. "You make up your mind: Do you want to be healthy? It's not a tough choice."
Barnard, 65, has worked with the Pritikin Longevity Center since 1978, and serves as a consultant. He weighs five pounds less than when he graduated from college, and his cholesterol dropped from 235 when he was in his early 40s to 180 when he changed his diet; he has maintained his cholesterol around 180-190 for more than 20 years.
The Pritikin program focuses on a diet of whole grains, fruits and vegetables, and small portions of meat (no more than 3-and-a-half ounces a day), and 60 minutes of exercise a day.
Prostate cancer is the most common type of cancer in American men, other than skin cancer, and the second leading cause of cancer death in men, exceeded only by lung cancer. Some 30,000 men in the United States die of prostate cancer each year.
Barnard noted that some people buy growth hormone supplements, which stimulate the production of IGF-I. He "seriously questions" older people taking such supplements.
"Where you need IGF-I is in your muscle; the way to get it is to exercise," Barnard said. "People want the easy way out; they want to take a pill."