Diet May Not
Prevent Prostate Cancer
NEW YORK (Reuters Health) - A diet that is low in fat and full
of fiber, fruits and vegetables is a good idea in general, but
it may not protect men against developing prostate cancer, US
These findings appear on the tail of previous research that
demonstrated that a high-fat diet is linked to an increased risk
of advanced prostate cancer.
So what's a man to eat? Lead author Dr. Moshe Shike of the Memorial
Sloan-Kettering Cancer Center in New York told Reuters Health
that although these results suggest that eating well may not protect
against prostate cancer, it nonetheless can have a powerful effect
on the eater's general health.
"In spite of this study, the low-fat, high-fruit, high-vegetable
diet is a healthy diet," Shike said.
This study "is by no means an indication not to follow this
diet," he added.
In terms of the seemingly contradictory results between the
current and previous findings, Shike noted that the two studies
used different techniques to obtain their results. Specifically,
in the first study, researchers asked men to remember their diets
over the past 3 to 5 years, and not many people can recall their
long-term eating habits with great detail, the researcher noted.
In contrast, the current study followed the men over time, a technique
considered to be more accurate by the research community, Shike
Shike's team measured the risk of prostate cancer in terms of
rising levels of PSA, a protein produced by the prostate gland.
Many cases of prostate cancer are only diagnosed when the disease
is at an advanced stage, so doctors try to catch the cancer in
its early stages by measuring PSA levels in the blood, with PSA
spikes signaling a man may have the beginnings of prostate cancer.
The investigators obtained their findings by following a total
of 1,350 men, half of whom received intense counseling to opt
for a low-fat diet that was rich in fiber, fruit and vegetables.
Shike and his colleagues then measured the men's PSA levels every
year for 4 years, and noted when any study participant was diagnosed
with prostate cancer.
Reporting in the September issue of the Journal of Clinical
Oncology, Shike and his team note that most men who were asked
to change their diets did so in the first year, and maintained
their healthy habits throughout the study.
However, the authors also write that the healthy diet appeared
to have no effect on how fast PSA levels increased in men, and
just as many men from both dietary groups had elevated PSA blood
levels throughout the study.
Furthermore, a similar number of men developed prostate cancer
in the two groups--19 of those whose diet was unchanged, and 22
men who had adopted the healthy eating habits.
Based on these findings, if a middle-aged man decides to switch
his diet to the one described in this paper, "that man cannot
expect that this diet, if consumed for 4 years, will reduce his
risk of developing prostate cancer," Shike said.
However, he noted that 4 years is not a very long period of
time to study the life cycle of cancer. Consequently, it is possible
that if a young boy were to adopt these healthy eating habits,
the diet could reduce his risk of developing prostate cancer once
he reaches middle age, Shike said.
In an accompanying editorial, Dr. Alan R. Kristal of Fred Hutchinson
Cancer Research Center in Seattle, Washington, notes that the
study findings appear sound, but may not present the whole picture
of the influence diet has on the risk of developing prostate cancer.
"We should remember that this study does not address whether
a low-fat and high-fiber dietary pattern affects very early processes
in carcinogenesis, before a detectable increase in PSA would occur,
nor does it address whether dietary change affects the development
of invasive disease," he writes.
SOURCE: Journal of Clinical Oncology 2002;20:3570-3571, 3592-3598.
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