Women who followed a regime of daily exercise and the Pritikin Diet, a diet low in fat and high in fiber-rich fruits, vegetables, and whole grains, lowered their levels of serum estradiol, insulin and insulin-like growth factor, all independent risk factors for development of breast cancer, according to results of a new study by UCLA researchers.

The researchers found that the serum changes reduced the growth and induced apoptosis (cell death) of breast cancer cells in in vitro laboratory testing.

"This is the first study to my knowledge to show that lifestyle changes can induce apoptosis, or cell death, in breast cancer cells" said James Barnard, Ph.D., professor of physiological science at UCLA and lead investigator of the study.

Barnard and UCLA colleagues studied 26 postmenopausal women who attended a 13-day program of diet and exercise at the Pritikin Longevity Center & Spa in Aventura, Florida. The researchers collected blood serum samples from the women on day 1 ("entry" samples) and day 13 ("exit" samples) of their Pritikin Program. In laboratories at UCLA, the women's bloodserums were placed in three different sets of culture dishes, each containing a different line of breast cancer cells.

Compared to the "entry" blood samples, the women's "exit" samples significantly decreased the rate of tumor cell growth in all three types of breast cancer. Adopting an exercise regime and a low fat, high-fiber diet resulted in serum changes that slowed the growth of breast cancer cells by as much as 19%.

The researchers also noted a 20 to 30% increase in tumor cell death (apoptosis) in the cell cultures using "exit" blood samples compared to those exposed to the "entry" samples.

"Overall, these results suggest that exercise combined with a Pritikin-type diet can result in a significant reduction in the risk for breast cancer," commented Dr. Barnard.

"This is exciting research because it shows that women can make changes in a very short period of time that can have a dramatic impact on their health - in this case, on the growth and death of breast cancer cells," said William McCarthy, PhD of UCLA's School of Public Health.

To understand what might be inhibiting tumor growth as well as destroying tumor cells, the scientists measured blood serum levels of estradiol (a form of estrogen), insulin, and insulin-like growth factor (IGF-1). All three have been identified as independent risk factors for the development of breast cancer.

By the end of the women's 13-day program at the Pritikin Longevity Center, all three risk factors had plummeted. Estradiol levels in the women on hormone replacement therapy fell on average 34%; among those not taking hormones, estradiol decreased 37%. Among all 26 women, insulin levels fell 29%, and IGF-1 levels dropped 19%.

The new study, funded by the University of California, Los Angeles, supports another study by UCLA researchers, announced in May at the American Society of Clinical Oncology's annual meeting. That study found that among more than 2,400 women who had been treated for early stage breast cancer, those who replaced many of the fatty foods in their diet with healthful low-fat foods like fruits and vegetables were significantly less likely to have their cancer return within the next five years than those who continued to eat a typically American high-fat diet.

"The epidemiological data indicates that lifestyle is a major factor in the development of breast cancer," commented Dr. Barnard. "Several large population studies have found that countries with the lowest intake of dietary fats have the lowest incidences of breast cancer, as well as colon and prostate cancer."

Conversely, women raised in affluent cultures like the United States, full of high-fat fare like French fries and cheeseburgers, suffer the highest rates of breast cancer in the world - an 80% increase compared to cultures like Okinawa, Japan, where dietary fat intake is low, about 20% of total calories, and intake of fresh, fiber-filled foods like fruits and vegetables is high.

Studies have found, too, that when women from low-breast-cancer-risk countries like Japan and China leave their traditional diets and migrate to countries like the U.S., their rates of breast cancer rise to the same high levels of their Western neighbors, and within just two generations.

"And as Asian countries like Japan are now becoming more Westernized, their breast cancer rates are going up substantially," noted Dr. Barnard.

"I've been telling people for years that 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 like Pritikin and do about an hour of aerobic exercise every day," said Barnard, who has published more than 100 studies over the past three decades on the relationship between healthful lifestyles and disease prevention.

Breast cancer is the most common cancer in U.S. women, and the second leading cause of cancer deaths in American women today (after lung cancer). The American Cancer Society estimates that in 2005, approximately 211,240 women in the United States will be diagnosed with invasive breast cancer.

For more information on UCLA’s department of physiological science, visit www.physci.ucla.edu/. For more information on UCLA’s School of Public Health, visit www.ph.ucla.edu/. For more information on the Pritikin Longevity Center & Spa, visit www.pritikin.com/.