of the classic criticisms levied by industry at concerns about synthetic
endocrine disrupting chemicals (EDCs) has been to point to all the
plant compounds that are in the human diet that are also capable
of acting as hormones. These plant compounds, called phytoestrogens,
are especially abundant in foods like soy.
on in the debate about Our Stolen Future, industry spokespeople
would trot out complex tables with calculations performed out to
4 decimal places showing that phytoestrogens were literally thousands
of times more abundant in our food than are synthetic compounds.
The tables looked very quantitative and precise, and proved to be
formidable tools in public presentations for audiences not familiar
with the science. What these tables really showed, however, was
that it is possible to be very precise but completely wrong.
appears less frequently now because it has been shown to be misguided.
What comes in through the mouth doesn't necessarily make it to
the fetus to influence fetal development.
of the plant compounds are de-activated even before being absorbed
by the gut, if they are absorbed at all. So they don't even make
it into the bloodstream, much less to the fetus.
that are absorbed into the blood are often deactivated or diminished
in quantity by natural chemicals in the blood, called serum binding
proteins, then act on the compounds that enter the blood. Serum
binding proteins are highly effective at binding some compounds
and not at others. On average, the binding proteins are more effective
against plant phytoestrogens than synthetic EDCs. Fortunately,
some EDCs are also "captured" by serum-binding proteins.
typically have far longer half-lives in the human body than do
phytoestrogens. Once ingested, the half-life of DDT can be a decade.
Phytoestrogens are far less persistent. They don't hang around.
but not all, synthetic EDCs bioaccumulate. Their chemical characteristics
result in their being stored in body fat. Over years of exposure,
they reach concentrations that can be thousands of times higher
than the levels found in the diet. Phytoestrogens, in contrast,
do not bioaccumulate.
essence, these differences between synthetic EDCs and phytoestrogens
are not about synthetic vs natural per se, but about specific
aspects of the chemistry of the molecules involved and the chemistry
of the human body. People possess chemical defenses which protect
against at least some of the phytoestrogens (see OSF Chapter
part because they avoid these defenses, persistent synthetic endocrine
disruptors accumulate in body tissue to levels that are orders of
magnitude of times higher than observed levels for phytoestrogens,
and some are then transferred to the developing fetus. Framing the
debate solely around the relative amounts of phytoestrogens vs.
synthetic chemicals that are encountered in the diet also ignores
the large exposures that can occur at the workplace or elsewhere
independent of food.
into this issue will no doubt reveal a far more complex picture
concerning natural defenses vs. synthetic and natural hazards.
Indeed, a key part of the ongoing research will explore why the
body's defense mechanisms are effective against some but not all
compounds. While far from the final word, these new results do,
however, counter the claim that the presence of plant estrogens
in the human diet is sufficient reason to dismiss concern about
synthetic compounds. It is clearly not.
the meantime, if you hear a speaker claiming that phytoestrogens
make synthetic EDCs irrelevant, understand that this person is either
way out-of-date as to how research on this has developed, shameless
in their willingness to use disproven arguments, or both.