Joe's
Herbs
Soy
No single food has generated as much interest in breast cancer prevention
than soy. That's because soybeans contain phytoestrogens. These are
plant-based chemicals that mimic the body's own estrogen. We know that
estrogen is implicated in breast cancer. We know that women who have
fewer pregnancies, have shorter periods, and are therefore exposed to
more estrogen over a lifetime are at increased risk. These phytoestrogens
that are found in soy are not as powerful as estrogen in stimulating
cells to divide. So the idea is that if you eat soy, it blocks the action
of the estrogen. There's some epidemiological evidence of that.
Japanese women, who have one quarter the breast cancer rate of North
Americans, consume 30 times as much soy products. We are not talking
about genetics, because when they move to North America they take on
North American dietary patterns and they take on North American cancer
patterns as well. A study from Singapore tells us that women who have
more phytoestrogens in their urine are less likely to develop breast
cancer in the future.
Other studies show that younger women who consume more soy products
are at reduced risk. But - there's always a fly in the ointment. Some
scientists suggest that while phytoestrogens are weak estrogens, if
you consume enough of them they will have a stimulant effect, which
is counterproductive. We can put our mind at ease, to some degree, over
this issue thanks to Dr. David Jenkins at the University of Toronto.
Dr. Jenkins fed large amounts of soy products to both men and women
and studied the effects. He found that the cholesterol was lowered,
which was expected. He also collected their urine because he wanted
to test the urine on human breast cancer lines for possible stimulatory
effects. He discovered that there weren't any. Dr. Jenkins now believes
that soy is protective. But what about postmenopausal women? There's
no reason to believe that incorporating soy products into the diet is
anything but beneficial.
Where the jury is out is with women who have been struck by this disease.
We don't have any good information that would tell us whether or not
these isoflavins present in soy beans are a good thing if the disease
is already established.
The prudent appoach, for someone who does have breast cancer, is to
not go overboard on the consumption of soy products. But the general
population can rest assured that we do have pretty significant evidence
that increased consumption of soy is preventative in terms of this terrible
disease.
