Flaxseed, diet may cut prostate
cancer risk
DURHAM, N.C.-- July
12, 2001 -- A low-fat diet supplemented with flaxseed may help
reduce the risk of prostate cancer, a small new study suggests.
The researchers report
in the July issue of Urology that dietary fat and fiber
can affect hormone levels and may influence cancer progression.
Lead author Dr. Wendy
Demark-Wahnefried from Duke University Medical Center says flaxseed
is high in fiber, lignan (a fiber-related compound) and a rich
source of plant-based, omega-3 fatty acids, all nutrients thought
to play a role in reducing cancer risk.
"Testosterone
may be important in the progression of prostate cancer, and lignan
in the flaxseed binds testosterone, so we thought the flaxseed
might suppress the growth of prostate cancer cells," said
Demark-Wahnefried in a press release.
"By pairing a
low-fat diet with the flaxseed supplement, we also thought we
could maximize the effect of the omega-3 fatty acids, since studies
in animals show that the kind of fat we eat may be important
for cancer progression," says Demark-Wahnefried, an associate
research professor in the department of surgery at Duke.
The pilot study involved
25 patients with prostate cancer who were awaiting prostatectomy
(surgical removal of the prostate). The researchers measured
levels of prostate-specific antigen (PSA), hormone levels and
total serum cholesterol at the beginning of the study.
The tumors of those
on the diet were then matched with 25 historic cases, equal in
age, race, PSA level at diagnosis and prostate tumor grade prostate
tumors to compare tumor progression and markers after the dietary
intervention.
The men were on the
low-fat, flaxseed-supplemented diet for an average of 34 days
that used specially-prepared finely ground flaxseed. In its natural
form, flaxseed is a pointy, tough seed that can puncture the
intestines when consumed in the amounts used in this study (three
rounded tablespoons a day).
The ground flaxseed
in the study was vacuum-packed (ground flaxseed can quickly go
rancid) and had added emulsifiers for ease of mixing. The men
were instructed to sprinkle the flaxseed on their cereal or mix
it into juices, yogurt or applesauce. Researchers reported good
compliance with the diet and said it was tolerated well.
At the end of the study,
the researchers observed that the men on the diet had significant
decreases in cholesterol, and both total and free testosterone.
While there was a decrease in testosterone levels, they noted
that none of the participants in the study suffered decreased
libido or sexual dysfunction. There was a trend toward a decrease
in PSA levels in men with early-stage prostate cancer, but in
men with advanced prostate cancer PSA levels continued to rise.
"It's not surprising
that a diet therapy that was only taken for an average of 34
days had little effect on men with aggressive disease,"
Demark-Wahnefried said. "But what we did see was that for
the men on the diet, their tumor cells did not divide as quickly
and there was a greater rate of apoptosis (tumor cell death)
in this group."
With such a short-term
dietary intervention, the researchers said they did not expect
to see a difference in tumor biology between the diet-treated
patients and the control patients, but were encouraged by the
lower proliferation rates and significantly higher rates of apoptotic
cell death.
Still, they said the
results should be interpreted with caution, stressing that randomized
controlled clinical trials are needed to confirm the results
of the pilot study. Research on mice models is currently under
way, and preliminary results support the findings in humans.
Demark-Wahnefried said
it is still unknown if the low fat diet or the flaxseed--or a
combination of the two--is the active component in the tumor
reductions, adding more studies examining these elements independently
are needed.
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