Science + Technology

UCLA Study Finds Low-Fat Diet Slows Prostate Cancer Growth in Lab Models

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A low-fat diet may help men with aggressive prostate cancer betterfight their disease and live longer, according to researchers at UCLA's JonssonCancer Center who showed that a diet low in polyunsaturated fats slowed cancergrowth and increased survival times in lab models.

The study appears in theFeb. 15 issue of the peer-reviewed journal Cancer Research. The study is partof the Jonsson Cancer Center's Specialized Program of Research Excellence inprostate cancer, a federally funded program created to find better ways toprevent, detect and treat this disease, which will strike more than 220,000American men this year alone.

Laboratory mice with advanced human prostate cancer that weredeprived of the hormone testosterone were fed a diet low in polyunsaturatedfats and remained in remission about twice as long as mice fed a diet with amuch higher fat content, the study found. The mice on the low-fat diet alsolived nearly twice as long as those on the high-fat diet, said Dr. WilliamAronson, a Jonsson Cancer Center researcher and the study's lead author.Additionally, levels of PSA which measuresthe amount of prostate cancer present were markedly lower in the mice fed a low-fat diet.

Aronson called the results "very significant," but cautioned thatlarge studies need to be conducted in humans to ensure the results can betranslated from mice to men.

"These results provide a sound basis for clinical trialsevaluating the impact of dietary fat reduction in prostate cancer patients onhormone therapy," said Aronson, an associate clinical professor of urology."This new finding tells us that a low-fat diet can impact cancer growth andsurvival times in laboratory mice. We need to understand why, and duplicate theresults in humans."

The research by Aronson andhis UCLA colleagues studied polyunsaturated fats, derived from corn oil andfound in the baked goods and fried foods popular in the American diet. The teamwanted to create a lab environment that would mimic a human population,specifically men with advanced prostate cancer treated with hormone therapy.

Standard treatment foradvanced prostate cancer is to stop production of the hormone testosterone,which drives cancer growth. Called androgen-deprivation therapy, this treatmentworks for a time. However, many men then develop cancers that are androgenindependent, meaning the cancers grow despite low levels of testosterone. Oncethat happens, hormone therapy is no longer effective and few other treatmentoptions are available, Aronson said.

In the Jonsson Cancer Center study, laboratory mice with humanprostate cancer were divided into three groups. One group was fed a high-fat diet containingabout 42 percent of calories from polyunsaturated fats. A second group of micewas castrated to mimic men onandrogen-deprivation therapy and fed a diet containing42 percent of calories from fat. The third group of mice, also castrated, wasfed a low-fat diet, with about 12 percent of calories coming from fat. Allthree groups ate the same number of calories, Aronson said.

The UCLA research team found that the uncastrated mice in thehigh-fat diet group had tumors that grew rapidly and the animals died quicklyfrom the cancer. Tumor growth in the castrated mice being fed a high-fat dietstabilized for a time mirroring whathappens to men with advanced prostate on hormone therapy. As expected, and asoften happens in humans, the cancers in this mice group then began to growagain. Meanwhile, the castrated mice on a low-fat diet went twice as long beforetheir cancers became androgen independent and began to grow again.Additionally, survival times were significantly longer in the low-fat dietgroup, and tumor size was much smaller than those found in mice on a high-fatdiet, Aronson said.

"This study may help us solve a clinical problem,how to prevent or delay androgren independence," Aronson said. "Maybe men onandrogen-deprivation therapy, if they eat a low‑fat diet, might prolongthe effectiveness of their hormone therapy."

Doctors have been recommending a diet low in fat forsome time, based on epidemiological studies offering evidence that such eatinghabits may help prevent certain cancers. This study is the first to show that alow-fat diet may help hormone therapy work better and longer, Aronson said.

"Now we need to do more detailed laboratory studies tofind out how the fat intake is affecting the growth of the androgen-independentcancers," Aronson said.

Human studies are several years away, Aronson said.However, men with prostate cancer can switch to a low-fat diet now and perhapsreap some benefit. Aronson suggests patients reduce their intake to about 15 to20 percent of calories from fat and combine that with daily exercise; forexample, taking a brisk walk or doing aerobic activity for 30 minutes everyday. Men also should eat more tomato products, particularly tomato paste, andmake sure the fat they do eat contains omega-3 fatty acids, the type found infish oils.

"I think dietary fat reduction, coupled with high fiberintake from fruits and vegetables in a variety of colors, can truly have animpact on prostate cancer prevention, and in combination with existingtreatments, perhaps increase survival times for patients," Aronson said.

UCLA's Jonsson Comprehensive Cancer Center is composedof 240 cancer researchers and clinicians engaged in cancer research,prevention, detection, control and education. One of the nation's largestcomprehensive cancer centers, the center is dedicated to promoting cancerresearch and applying the results to clinical situations. In 2003 the center was named the best cancer center in theWestern United States by U.S. News & World Report, a ranking it has heldfor four consecutive years.

For more information on the Jonsson Cancer Center, visit www.cancer.mednet.ucla.edu/.

-UCLA-

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