“How to Block Breast Cancer’s
Estrogen-Producing Enzymes” The vast majority of breast cancers
start out hormone dependent, meaning the primary human
estrogen, called estradiol, plays a crucial role in breast
cancer development and progression. That’s one of the reasons
why soy food consumption appears so protective
against breast cancer, because soy phytoestrogens, like
genistein, act as estrogen-blockers; they block the binding of
estrogens, like estradiol, to breast cancer cells. But, wait a second; the
majority of breast cancers occur after menopause
when the ovaries have stopped producing estrogen. What’s the point of
eating estrogen blockers if there’s no
estrogen to block? It turns out the breast cancer tumors
themselves produce their own estrogen from scratch to fuel
their own growth. Estrogens may be formed in
breast tumors by multiple pathways. The breast cancer takes
cholesterol and, using the aromatase enzyme or two
hydroxysteroid dehydrogenase enzymes, produces its
own estrogen. So, there’s two ways
to stop breast cancer. One is to use anti-estrogens,
estrogen blockers, like the soy phytoestrogens, or the anti-estrogen
drug tamoxifen. However, another way
to block estradiol is by using anti-enzymes to
prevent the breast cancer from making all the
estrogen in the first place. And indeed, there are a variety of
anti-aromatase drugs in current use. In fact, inhibiting the
estrogen production has been shown to
be more effective than just trying to block
the effects of the estrogen, suggesting that the inhibition
of estrogen synthesis is clinically very important
for the treatment of estrogen-dependent
breast cancer. It turns out soy
phytoestrogens can do both. Using ovary cells taken from women
undergoing in vitro fertilization, soy phytoestrogens were
found to reduce the expression of the
aromatase enzyme. What about in breast
cancer cells though? Breast cancer cells too. Not only suppressing
aromatase activity, but the other estrogen-
producing enzyme too. But, this is
in a petri dish. Does soy suppress estrogen
production in people too? Well, circulating estrogen levels
appear significantly lower in Japanese women than
American white women, and Japan does have the highest
per capita soy food consumption, but you don’t know
it’s the soy until you put
it to the test. Japanese women were randomized
to add soymilk to their diet or not for
a few months. Estrogen levels did seem
to drop about a quarter in the soymilk-supplemented group Interestingly, when they tried
the same experiment in men, they got similar results: a significant drop in
female hormone levels, with no change in
testosterone levels. These results, though, are
in Japanese men and women that were already consuming
soy in their baseline diet; so, it was
really just looking at higher versus
lower soy intake. What happens if you give
soymilk to women in Texas? Circulating estrogen
levels cut in half. Since increased estrogen
levels are a marker for high risk for breast cancer,
the effectiveness of soy to reduce estrogen
levels may help explain why Chinese and Japanese women
have such low rates of breast cancer. And, what was
truly remarkable is that estrogen levels
stayed down a month or two even after they
stopped drinking it. This suggests you don’t have
to consume soy every day to have the cancer
protective benefit. Video source: https://www.youtube.com/watch?v=AvSLeoUVb54
