"Should Women with Fibroids Avoid Soy?"
About 1 in 4 women will eventually suffer from fibroids,
most commonly manifesting as excessively
heavy periods and pain or pressure.
Why might you feel pressure?
Because you may be carrying around 26 pounds
of tumors in your uterus.
Fibroids are the most common reason women get hysterectomies—
having their uterus removed completely,
a major surgery associated with disability and death,
but all surgery carries risk.
The chances of dying within a month of surgery
may only be about 1 in 1200,
which makes it among our safest surgeries,
safer than getting your gallbladder removed, for example.
But, of course, you lose the ability to bear children,
and costs billions of dollars a year.
Yet, despite the high prevalence,
significant pain and suffering, and huge economic impact,
relatively little is understood about the cause
and disease process that lead to fibroid tumors.
Avoiding atomic bomb blasts whenever you can
is probably a good idea in terms of decreasing fibroids risk,
but what about more easily modifiable risk factors?
Well, alcohol consumption is associated
with increased risk, particularly beer,
and whenever you hear that, whenever you hear beer specifically,
you think of the hormonal effects specific to beer,
specifically the powerful phytoestrogen found in hops.
Well, if that phytoestrogen is increasing fibroids risk,
what about the phytoestrogens in soy?
Well, this was looked at in the Black Women’s Health Study.
Fibroids are 2 to 3 times more prevalent
among African-American women;
so, they thought maybe dairy intake
might be contributing to the disparity,
given their higher levels of lactose intolerance.
And indeed, dairy consumption
was associated with reduced risk.
They figured it was the calcium content
or maybe the vitamin D,
but perhaps the women were drinking soy milk
instead and that was increasing their risk?
No, soy intake was found to be unrelated,
same finding in a group of predominantly white women,
though they did note a protective association
with the amount of lignans flowing through their bodies.
Lignans are another class of phytoestrogens
found predominantly in flaxseeds,
but throughout the plant kingdom.
Hard to make any generalizations
about soy phytoestrogens, though,
as soy consumption was rather low across the board.
This was done in Washington state.
If you go to Japan,
where they have the highest per capita
soy consumption in the world,
you could get a bigger spread of intakes.
The researchers had previously found
that soy intake was inversely associated
with the risk of hysterectomy,
meaning women who ate more soy
had lower hysterectomy rates,
suggesting a potentially protective effect
of soy against uterine fibroids,
since that’s the main reason
women have their uterus removed.
This would be consistent with in vitro studies
that found that the main soy phytoestrogen
seemed to inhibit fibroid tissue proliferation in a petri dish.
But, when they specifically looked,
there was no evidence of a link to soy at all,
protective or otherwise.
The same was found in one study out of China.
Fruit and vegetable intake was associated with
significantly lower risk of fibroids,
but soy food consumption was not.
But a second study out of China, published the same year,
found a significant association
between soymilk intake and fibroids.
That’s consistent with the three alarming case reports
of women with symptomatic fibroids
reporting an “unusually” high intake of soymilk,
or regularly consuming “excessive” amounts of soy,
or “extremely high” intakes of soy
every day for decades.
It's hard to take these cases seriously
when nowhere do they actually say
how much they were consuming.
The only quantitative mention was 40 grams of isoflavones,
which roughly translates to 400 gallons
of soymilk every day—
that would be excessive, but also impossible.
The only way to know for sure is to put it to the test.
Not just a population study or anecdotal reports
but randomize women to two years of soy phytoestrogens—
the amount found in 3 to 5 cups of soymilk a day—
and no significant effect
on the frequency or growth of fibroids was found.