Low-fat Diet Extends Prostate Cancer Response to Hormonal Suppression, May Extend Survival
A low-fat diet may help men with aggressive prostate cancer better fight their disease and live longer, according to researchers who showed that a diet low in polyunsaturated fats slowed cancer growth and increased survival times in lab models.
reported by J. Strax
PSA Rising, New York. February 15, 2004 — Controversy surrounds the long term benefits of the Atkins and the South Beach Diets for healthy but overweight Americans. For people who have already received diagnosis and treatment for cancer, dietary choices are even more sensitive.
For men who have been treated for prostate cancer, some evidence suggests that a low fat diet high in fruits and vegetables (plus daily exercise) is beneficial. Now researchers are looking at whether dietary changes can benefit men with advanced prostate cancer.
A low-fat diet may help men with aggressive prostate cancer better fight their disease and live longer, according to researchers at UCLA’s Jonsson Cancer Center, who showed that a diet low in polyunsaturated fats slowed cancer growth and increased survival times in lab models.
The study appears in the Feb. 15, 2004, issue of the peer-reviewed journal Cancer Research. The study is part of the Jonsson Cancer Center’s Specialized Program of Research Excellence (SPORE) in prostate cancer, a federally funded program created to find better ways to prevent, detect and treat this disease, which will affect more than 220,000 American men this year alone.
Laboratory mice with advanced human prostate cancer that were deprived of the hormone testosterone were fed a diet low in polyunsaturated fats and remained in remission about twice as long as mice fed a diet with a much higher fat content, the study found. The mice on the low-fat diet also lived nearly twice as long as those on the high-fat diet, said Dr. William Aronson, a Jonsson Cancer Center researcher and the study’s lead author. Additionally, levels of PSA – which measures the amount of prostate cancer present – were markedly lower in the mice fed a low-fat diet.
Aronson called the results “very significant,” but cautioned that large studies need to be conducted in humans to ensure the results can be translated from mice to men.
"These results provide a sound basis for clinical trials evaluating the impact of dietary fat reduction in prostate cancer patients on hormone therapy," said Aronson, an associate clinical professor of urology. "This new finding tells us that a low-fat diet can impact cancer growth and survival times in laboratory mice. We need to understand why, and duplicate the results in humans."
The research by Aronson and his UCLA colleagues studied polyunsaturated fats, derived from corn oil and found in the baked goods and fried foods popular in the American diet. The team wanted to create a lab environment that would mimic a human population, specifically men with advanced prostate cancer treated with hormone therapy.
Standard treatment for advanced prostate cancer is to stop production of the hormone testosterone, which drives cancer growth. Called androgen deprivation therapy, this treatment works for a time. However, many men then develop cancers that are androgen independent, meaning the cancers grow despite low levels of testosterone. Once that happens, hormone therapy is no longer effective and few other treatment options are available, Aronson said.
In the Jonsson Cancer Center study, laboratory mice with human prostate cancer were divided into three groups. The groups were fed as follows:
- a high-fat diet containing about 42 percent of calories from polyunsaturated fats.
- for a group of mice that were castrated – to mimic men on androgen deprivation therapy – a diet containing 42 percent of calories from fat.
- a third group of mice, also castrated, were fed a low-fat diet, with about 12 percent of calories coming from fat.
All three groups ate the same number of calories, Aronson said.
Findings verified the hypothesis that low fat would reduce rate of prostate cancer tumor growth and increase survival. The UCLA team found that:
- the uncastrated mice in the high-fat diet group had tumors that grew rapidly and the animals died quickly from the cancer.
- the castrated mice fed a high-fat diet stabilized for a time — mirroring what happens to men with advanced prostate on hormone therapy. As expected, and as often happens in humans, the cancers in this mice group then began to grow again.
- the castrated mice on a low-fat diet went twice as long before their cancers became androgen independent and began to grow again. Additionally, survival times were significantly longer in the low-fat diet group, and tumor size was much smaller than those found in mice on a high-fat diet.
"This study may help us solve a clinical problem, how to prevent or delay androgren independence," Aronson said. "Maybe men on androgen deprivation therapy, if they eat a low-fat diet, might prolong the effectiveness of their hormone therapy."
This study did not not test the effects of low-fat diet on tumors in mice that had not been castrated. (They do not state why not.)
Some prostate cancer patients have been opting for low-fat diets for some time. Some doctors have been recommending a diet low in fat based on epidemiological studies offering evidence that such eating habits may help prevent certain cancers. According to Aronson, this study is the first to show that a low-fat diet may help hormone therapy work better and longer.
"Now we need to do more detailed laboratory studies to find out how the fat intake is affecting the growth of the androgen independent cancers," Aronson said.
Human studies are several years away, Aronson said. However, men with prostate cancer can switch to a low-fat diet now and perhaps reap some benefit. Aronson suggests patients reduce their intake to about 15 to 20 percent of calories from fat and combine that with daily exercise, for example taking a brisk walk or doing aerobic activity for 30 minutes every day. Men also should eat more tomato products, particularly tomato paste, and make sure the fat they do eat contains omega-3 fatty acids, the type found in fish oils.
"I think dietary fat reduction, coupled with high fiber intake from fruits and vegetables in a variety of colors, can truly have an impact on prostate cancer prevention, and in combination with existing treatments, perhaps increase survival times for patients," Aronson said.
Wiiliam Aronson is an associate Clinical Professor of Urolgy at UCLA.
A January 2003 UCLA study found that Exercise and Dietary Changes Can Kill Prostate Cancer Cells, UCLA Scientists Report.
Prostate Cancer Program at UCLA's Jonsson Cancer Center Designated a Site of Research Excellence by the NCI; $11.5 Million Grant Awarded - Oct. 2002.
In 2003, the center enter was named the best cancer center in the western United States by U.S. News & World Report, a ranking it has held for four consecutive years.
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