Proper functioning of the body's many systems requires that a
constant internal environment be maintained. This state is called
homeostasis. The body achieves homeostasis through two main
control systems. First is the nervous system and second is the
endocrine system. The endocrine system consists of glands and
cells that secrete chemicals called hormones into the blood.
These hormones then travel through the blood towards
various cell targets, where they maintain homeostasis. Whether
it's regulating metabolism, proper growth and development,
ion levels, water balance, blood pressure, reproduction, or
immunity, the endocrine system wears many hats within the body
to ensure homeostasis. As you can imagine, proper functioning
of the endocrine system is therefore integral to
maintaining health. A challenge to proper endocrine function,
however, are endocrine disruptors, which are chemicals
that interfere with the proper functioning of the endocrine
system. Given that the endocrine system has such a widespread
role in maintaining homeostasis, it is not surprising that
endocrine disruption is also associated with a myriad of
health outcomes. For instance, dioxins are disruptors which can
be produced from volcanoes, but nowadays are mostly byproducts
of human processes, such as incineration of plastics, and
paper production. These molecules are fat soluble,
meaning that they can accumulate in the body's fat tissues. They
can also persist in the body for up to eight years, Studies have
related heavily exposed subgroups to an increase in
cancers, nervous system degeneration, immune damage,
thyroid disease, and reproductive and sexual
developmental disorders. However, not all endocrine
disruptors are so clear cut in their definition. For instance,
phytoestrogens are another class of endocrine active
compounds which have been associated with varying effects
on human health. However, many studies of these compounds are
characterized by very small sample sizes, which are known to
amplify the effects of random variation, as well as possible
conflicts of interest stemming from funding by manufacturers of
soy and related supplements. But first, let's discuss what a
phytoestrogen is. phytoestrogens are naturally
occurring plant compounds whose molecular structure resembles
that of vertebrate steroid estrogens. Isoflavones are
considered to be among the most estrogenic phytoestrogens,
helping mostly to develop and maintain female sex
characteristics. Owing to their richness in these compounds, soy
beans and soy foods also became a subject of study. Soy contains
three main types of isoflavones: genistein, daidzein and glycine.
Since they were first researched in the 1990s, isoflavones have
almost always been associated with controversy. In fact,
isoflavones first came to attention as a result of
breeding problems experienced by Australian sheep, which had been
grazing in the fields of isoflavone rich clover. This
led researchers to first question whether isoflavones
could be culpable in impaired fertility among humans. In
humans, isoflavones are processed into several
compounds, many of which are estrogenic. Chief among these is
equol, which is even more estrogenic than its isoflavone
precursor. The reason for isoflavones' endocrine activity
stems from the fact that both isoflavones and estrogen use the
same molecular pathways. When hormones interact with target
cells, they do so through receptors, just like how you
need to key to get through a locked door. Sometimes, these
receptors may be on the surface of the cell, or sometimes they
may occur within the cell, like nuclear receptors, which bind
the cell's DNA. Estrogenic compounds, like estrogen itself,
bind to estrogen receptors, which are present in several
cell types, including the brain, bones, lungs, skin, testes,
uterus, and kidneys. This changes the types of signals
occurring within the cell and which proteins the cells make.
Phytoestrogens, like estrogens, can also bind to these
receptors, although not as strongly. At lower
concentrations, they act in a similar way to normal estrogens,
but at a high concentration, their effect is reversed, as the
compounds antagonize the activity of the estrogen
receptors. Since phytoestrogens may be consumed in large
amounts, it is not atypical to have vitae estrogen levels many
times greater than the body's own estrogens making up for the
difference in binding strength. In the 1990s, the isoflavone
controversy began as genestein was shown to stimulate the
growth of mammary tumors in mice. This was supported by two
other studies conducted a few years after. While downsides to their
use of been documented, isoflavones aren't all bad. In
fact, nowadays, we recognize several benefits in humans. For
example, isoflavones protect against the effects of
chemotherapy, especially in breast and prostate cancers.
They have also demonstrated a reduction in some symptoms of
menopause and have been related to lower incidences of heart
disease. Isoflavones, especially genestein, have been related to
improve bone formation, potentially reducing the bone
loss associated with osteoporosis. So,
what is it? Do they cause or prevent illness? Well, as you
can tell, the research is divided and largely ambiguous.
Currently, many toxicology and food safety commissions around
the world are evaluating the safety of isoflavones in young
children. Given the increasing interest in plant-based diets
and the prevalence of soy infant formula, it is important that
isoflavones and their health effects be well studied. So, now
for our original question. Are isoflavones the phytoestrogens,
truly endocrine disruptors? Well, that's a question of how
we define them. The World Health Organization defines endocrine
disruptors as substances that alter the function of the
endocrine system and consequently cause adverse
effects in the intact organism, its progeny or populations of
the organism. Adverse effects can include changes in
appearance, physiology, growth, development, or lifespan. While
there is recognition that isoflavones act on the endocrine
system making them endocrine active substances, they are not
necessarily endocrine disruptors, because adverse effects depend
on the background physiological situation. While adverse effects
have been documented in animals. There's a growing body of
evidence suggesting that endocrine disrupting effects
observed in animals cannot be extrapolated to humans. But what
does this mean to you? Should you be worried about consuming
soy products? Well, many populations around the world
consume soy products regularly and in large quantities. While
they mostly consume traditional soy foods derived from whole soy
beans, rather than soy ingredients or soy protein
products, studies of Asian populations have demonstrated
decreased incidences of breast cancer, prostate cancer and
menopause symptoms compared to Western populations. As well, soy
infant formulas have been given to children over the decades, and
have been associated with normal growth and development in full-term
infants. Nevertheless, this video should not be taken as
medical advice and any substance can cause harm if given at a
high enough dose. To quote the Swiss physician Paracelsus, "What
is there that is not poison? All things are poison and nothing is
without poison".