Soy Cancer Warning
by Clair
Weaver
(Source:
NEWS.com.au)
January 14,
2007 12:00
soy-cancer-warning.jpg
CANCER
patients are being warned to avoid foods rich in soy because they can
accelerate the growth of tumours.
The Cancer
Council NSW will issue guidelines today, warning about the dangers of
high-soy diets and soy supplements for cancer patients and those people
in remission from cancer.
At
particular risk are people suffering from hormone-dependent cancers,
including breast and prostate cancer - the two most common types of
cancer in Australia.
Cancer
survivors are also being urged to avoid high doses of soy, as they may
be more vulnerable to a relapse.
Research
has found high consumption of soy products can also limit the
effectiveness of conventional medicines used to treat the disease.
"There is
evidence to suggest that women with existing breast cancer or past
breast cancer should be cautious in consuming large quantities of soy
foods or phyto-oestrogen supplements,'' a position statement from the
Cancer Council says.
"Women with
current or past breast cancer should be aware of the risks of potential
tumour growth when taking soy products.
"The Cancer
Council does not support the use of health claims on food labels that
suggest soy foods or phyto-oestrogens protect against the development
of cancer.''
Health
experts are particularly concerned that breast-cancer sufferers who
take soy or phyto-oestrogen supplements could feed the disease and
reduce the effectiveness of their treatment.
Soy, which
is present in soy beans, soy milk, tofu, tempeh and some breads,
contains phyto-oestrogens that mimic the actions of hormones in the
body.
This means
it may interfere with cancer drugs such as Tamoxifen, which works by
suppressing the female hormone oestrogen.
Men with
prostate cancer are also being warned against high soy consumption, as
phyto-oestrogens may imitate the male hormone androgen.
Although
the Cancer Council has warned against soy supplements, it believes an
occasional intake of soy food is still safe for cancer patients.
Cancer
Council nutritionist Kathy Chapman said soy supplements could contain
dangerously high doses of phyto-oestrogens.
"If you
were a woman with breast cancer and thought, 'I'm going to radically
change my diet and have very large portions of soy at every meal', it
could be a problem,'' Ms Chapman said.
"For
someone who has tofu once or twice a week and drinks a bit of soya
milk, it's not so much of a problem.''
Soy has
earned a reputation as a natural "superfood'' that cuts the risk of
breast or prostate cancer, and is commonly included in women's health
supplements.
This claim
was based on findings that cancer rates were lower in Asia, where soy
consumption is high.
But soy
would lower the risk of contracting cancer "only a little'', according
to the Cancer Council.
"While they
may have a protective effect, there is also some evidence that
phyto-oestrogens may stimulate the growth of existing hormone-dependent
cancers,'' the council's statement said.
The risk of
contracting other non-hormone-dependent cancers, including bowel
cancer, would be unaffected by soy intake.
The Cancer
Council was prompted to investigate the issue after being inundated
with questions about the role of soy in cancer patients' diets.
"We felt we
were getting a lot of calls on our hotline about this topic,'' Ms
Chapman said.
Breast-cancer
survivor Susie Musarra was surprised by the new evidence about soy.
The Sydney
mother of two was diagnosed five years ago. She followed a healthy
diet, containing plenty of fruit and vegetable juices, during
chemotherapy treatment.
"It's
really confusing, because you get a lot of conflicting information
about what to eat,'' she said. "It's good to have this advice, because
it helps you make an informed decision - and the Cancer Council is a
reputable source.''
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