Low-fat Diet
Extends Prostate Cancer Response to Hormonal Suppression, May Extend Survival
Source:
psa-rising.com/eatingwell/low_fat_2004.htm
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.
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