We've all heard the old adage
'you are what you eat.' Lately, medical science is pushing
the message that even if you're not going to turn into
your dinner, what you downed for lunch may have more far
ranging consequences than a spot of indigestion. In this
vein, it's been noticed that not only are diets vastly
different between East and West, but so are rates of endometrial
cancer.
Endometrial cancer lies in
fourth place among new cancers in Canadian women, while
in the Far East, on the other hand, rates are three
to five times lower. This has fuelled the belief that
endometrial cancer rates can be dramatically influenced
by the soy content of diets. This is because soy foods
are rich in isoflavones, a major group of phytoestrogens,
which have been shown to alter endogenous estrogen concentrations.
Until the recent publication of a study in the May 29
issue of the British Medical Journal, however,
no large studies have put this relationship to the test.
This five-year study, led by Xiao Ou Shu of Vanderbilt
University in Nashville, enrolled 832 Shanghai women
diagnosed with endometrial cancer, and compared their
interview responses to 846 age-matched healthy controls.
There were no major differences between cases and controls
with respect to marital status, family income, total
energy intake or use of hormone replacement therapy.
However, compared with controls, cases were more educated,
younger at menarche and older at menopause, had higher
body mass indexes and waist to hip ratios, and were
less likely to exercise regularly, drink alcohol or
use oral contraceptives.
Cases were also more likely to have a family history
of cancer, to have been pregnant fewer times, and consumed
more meat and fish. Surprisingly, no significant differences
existed between cases and controls for fruit and vegetable
intake.
There were, however, differences for soy intake. Women
who consumed more soy had a two-thirds lower risk of
endometrial cancer than those who didn't consume as
much. This relationship was most pronounced among women
with a higher body mass index or a higher waist to hip
ratio.
These findings alone don't explain global incidence
rates of endometrial cancer, which vary more than 10-fold
worldwide. While the average intake of isoflavones from
soy food among these Shanghai women was about 25 times
greater, genetic predisposition and the lower birth
rate among Western women are also at work.
Although endometrial cancer is closely linked to estrogen
levels and soy is anti-estrogenic, none of this suggests
that soy is protective against cancer generally. There
may be other factors involved. This study suggests that
fruit and vegetable intake is irrelevant to risk of
the disease, a finding that would be truly bizarre in
less hormonally-dependent cancers.
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