What Are the Hidden Costs of Modern Hygiene?
Chris Kresser: Sure. I can just give a brief topline summary. We’ve talked about this before in more detail when we had Moises Velasquez-Manoff, author of An Epidemic of Absence, on the show
to talk about the “old friends” or hygiene hypothesis, which is the
idea that we co-evolved with certain microorganisms that turn out to
play a crucial role in regulating our immune system, and the
disappearance of those microorganisms over the last hundred years in the
industrialized world has led to a dramatic increase in chronic
inflammatory disorders that can basically be separated into three
categories: autoimmune disease, allergies, and then just general
inflammatory conditions like asthma and arthritis, eczema, psoriasis,
etc.
There’s a lot of evidence to support this hypothesis. You can look
at epidemiological studies which show that the incidence of these
inflammatory conditions is basically a mirror image of geographical maps
of the incidence of helminth infections. Helminths are worm-like
parasites that are considered to be “old friends,” meaning we evolved
over a very long period of time with them, and they plan an important
role in regulating our immune system. And so if you look at maps of
helminth infections, they’re basically a flip-flop of maps of chronic
inflammatory diseases, and the same is true when you look at levels of
exposure to things like saprophytic mycobacteria, which is a kind of
bacteria that are present in soil and untreated water that we’ve been
exposed to throughout our entire evolutionary history but is
increasingly absent in the modern environment because of changes.
Essentially there is what we might call, not just a Paleolithic approach
to food, but there’s a Paleolithic microbiome, and that microbiome has
profound impacts on our physiology and particularly our immune system,
and the shift in that microbiome may actually even be more important in
some ways in terms of its effect on our health than the shift from a
hunter-gatherer lifestyle to agriculture.
You may remember, Steve, when I talked about this in my presentation,
what’s really interesting is there’s the theory that’s prevalent in the
paleo community that the shift from a hunter-gatherer lifestyle to
agriculture led to an increase in inflammatory disease and worsening in
health, and there’s no doubt that there’s evidence that moving from a
hunter-gatherer lifestyle to agriculture did lead to a decline in
certain measures of human health, but the idea that compounds like
gluten and saponins and lectins and capsaicin in peppers were
responsible for this decline isn’t very well supported by the evidence
because the significant increases in chronic inflammatory disease didn’t
happen, really, until the last hundred years, and the change from a
hunter-gatherer lifestyle to agriculture happened a full 10,000 years
ago at least, maybe more like 11,000 or 12,000 years ago in certain
areas. So there has to be something else that explains this because if
it was true that gluten and capsaicin and lectins significantly increase
the risk of inflammatory disease, it would have done that a lot longer
ago than it actually did. And when you look at the evidence, one of the
things that might clarify this or tie this together is it’s possible
that those compounds in Neolithic foods are not a significant risk
factor for inflammatory disease as long as the Paleolithic microbiome is
still intact, whereas if the Paleolithic microbiome has been depleted
or altered by sanitation and hygiene and other aspects of the modern
lifestyle, then those foods do become risk factors for inflammatory
disease.
I think actually this is probably the most important part of my whole
talk, and it was a little bit buried in there. I hope it came across
clearly because, for me, this has been one of the big challenges of
resolving some of the apparent conflicts in this ancestral paradigm, is
that if you ever talk to someone who’s well informed about anthropology
and the history of human health and you say to them that grains have
significantly increased the risk of inflammatory disorders, they might
turn around and say: Really? Well, how did that not happen when all of
these cultures were eating grains for thousands of years and those
disorders were incredibly rare? Weston A. Price, for example, studied
the people in the Lötschental Valley in Switzerland and the Scottish and
Gaelic living in the Outer Hebrides both of whom relied on grains and
dairy as staples. And then there are contemporary agricultural
communities in South America and other parts of the world that really
rely on tomatoes and grains and other foods that contain these Neolithic
compounds, and yet autoimmune disease and asthma and things like that
are really rare in those places.
We have to be able to resolve that contradiction if we want people to
take us seriously when we talk about this diet, and so this “old
friends” hypothesis is a way of really tying that together. And the way
I would explain it to people now is by saying, look, it’s possible that
if we still had the Paleolithic microbiome intact, we could tolerate
grains and all of these compounds with no problem. And perhaps that
explains why some people are able to tolerate those foods with
apparently no problems. But given that the microbiome has changed so
significantly because of things like sanitation and hygiene and also
increased use of antibiotics and decline in the consumption of fermented
foods and fermentable substrates that lead to a better gut microbiome,
and increased use of soaps, which actually deplete the skin from certain
types of ammonia-oxidizing bacteria that we’ve evolved with for a long
time, a decline in breastfeeding – because of all of that, these foods
which didn’t really bother us that much for many thousands of years when
our microbiome was still intact are now significant risk factors for
inflammatory disease, and that’s the reason why I tend to recommend that
people avoid or minimize them because we’re not living with that
microbiome still intact, and there are many other aspects of the modern
lifestyle that are problematic and hostile to our immune system. So
given all of that, it makes sense to me to minimize the inputs that
could potentially dysregulate the system in spite of the fact that it’s
theoretically possible and even epidemiologically likely that those
foods are not the sole cause of an increase in inflammatory disorders.
Steve Wright: So if I understand what you just said and if I
understood the talk correctly, basically the prevalence of a different
gut microbiome, which your talk specifically centered in on some
specific parasites, but also talked about how there was typically
probably a completely different makeup because we know that that changes
based on what you eat and where you live and everything, but if we
focus more on this other microbiome, then it basically modulated the
immune system so it made us less reactive to potential problematic foods
or other things in our environment, right?
Chris Kresser: Yep. That’s pretty much it. Let’s take
helminths as an example. These are the worm-like parasites that we
co-evolved with for millions of years, and in fact, helminth infections
first started between 564 and 528 million years ago, so we’re talking
about a very, very long time. There’s evidence that not only all
humans, not only all hominids, not only all mammals, but all vertebrates
in the history of evolution have been exposed to helminths and infected
by helminths. And if that’s true, which it certainly seems to be,
based on the fossil record, then there’s actually evidence suggesting
that the adaptive immune system, which is one part of our immune system
that evolved in response to helminth infection, which indicates that our
immune system can’t really even function as it was designed to do
without helminths being present, which is kind of a mind-blowing
concept, right?! That are immune system is really not normal if
helminths, which are parasites, are not present, and I think that’s a
difficult concept to grasp. We’re conditioned to think that parasites
are harmful, and of course, some are. Some are very harmful. This is
not to suggest that we have this relationship with all parasites. But
helminths have been around for a long time, and our immune system is
tuned to expect their presence.
What they do is they have gently suppressed inflammatory responses,
and that has acted as a type of brake, if we’re going to use an
analogy. Our immune system has one foot on the brake throughout most of
its history, and then there are these other genetic variants that were
selected for that restored inflammatory responses when helminths were
present. Why would this happen? Well, let’s say you live in an area
where malaria is endemic, and inflammation is the body’s way of fighting
malaria off, so if you had helminths that suppress your inflammatory
response, that could potentially be a disadvantage in that situation,
and any genetic variants that arose that restored inflammatory responses
in that situation would have been selected for. Those genetic variants
were like having one foot on the accelerator, so we had one accelerator
and one foot on the brake, and it kept our immune system in a type of
dynamic balance. Then all of a sudden in the last hundred years or less
– because in 1947 in Europe, for example, a third of the population or
more than a third still had helminths; we’re talking about a relatively
recent period of time – helminths completely disappeared from the
environment and from our guts, and so that foot on the brake that was
providing that dynamic tension with the accelerator, so to speak, was
gone, and the pedal was to the metal [indiscernible] this really
dramatic epidemic of inflammatory disease because there’s nothing now
that’s preventing excess inflammation that’s caused by those genetic
variants.
Steve Wright: This wasn’t part of your talk, but I think it’s
a question on my mind and probably others who watched your talk: How
do we start to reconcile the fact that only some of us – well, it is a
big enough portion of the population – are having allergies, asthma,
inflammatory disorders, but nowhere near the majority yet are having
those? Are do we begin to reconcile that? We know that everything has
changed. The food has changed, the environment has changed, and the
microbiome has changed, and there are only some of us who are extremely
affected by this.
Chris Kresser: Well, actually 1 in 2 people now has allergies
in the industrialized world, so that is nearly a majority, and it’s
shocking when you really contemplate it. It’s 1 in 10 for autoimmune
disease, and it’s tens of millions for chronic inflammatory conditions.
The numbers are pretty impressive when you think about it, but
nevertheless, the answer to that question, I already alluded to it.
It’s a combination of genetic susceptibility, so I just talked about
these genetic variants that evolved in places where other acute
infections were endemic, like malaria, and they evolved as a way of
protecting us from those life-threatening infections, especially when
helminths were present because helminths kind of suppressed the immune
response or the inflammatory response, and that’s beneficial in a
certain way in that it protects us from autoimmune disease and allergies
and inflammatory conditions, but it’s potentially harmful when we can
get an infection like malaria and die unless we’re able to mount a
sufficient inflammatory response.
There were certain areas where those genetic variants were selected
for and more common. An example of this is Sardinia. Right now in
Sardinia, 1 in 430 people has multiple sclerosis, and 1 in 270 has type 1
diabetes, which are extraordinarily high rates when you consider the
global averages. So why are rates so high there? Well, malaria was
very common in Sardinia up until it was eradicated from the island in
the 1950s, and so all the people who live on Sardinia had these genes
that promoted inflammation in order to help them fight off malaria
infection, and as long as malaria was present at the same time, those
genes didn’t lead to excess inflammation because the malaria was keeping
it in check. But then when malaria was eradicated from the island in
the 1950s, everyone still had those genes that promote excess
inflammation, but the malaria was no longer keeping it in check, so
those genes, all of a sudden, became a risk factor for autoimmune
disease.
So definitely genetic predisposition is playing a big role here.
Some people have these genetic variants that promote inflammation, and
if they had helminths, those genetic variants wouldn’t be an issue and
they wouldn’t be subject to an increased risk of autoimmune disease.
And not just helminths, also the saprophytic mycobacteria and early
exposure maybe even to certain viruses, like hepatitis A, and certain
bacteria, like H. pylori, which is harmful later in life but may even be
protective earlier in life. There are all these different aspects of
the microbiome that help suppress inflammatory responses and protect
against any excessive inflammation that would have been caused by these
genetic variants. So that’s number one. And then number two is just
exposure to other aspects of the modern lifestyle that predispose us to
autoimmune disease and inflammatory conditions. For example, if you’ve
taken a lot of antibiotics when you were a kid, that had a significant
impact on the microbiome, which, again, as I mentioned, shifts our
susceptibility to inflammatory disease. It makes it more likely that
you’ll have a leaky gut, which Dr. Fasano, who we’ve had on the show in
the past, suggests is a big risk factor for autoimmune disease and may
even be a precondition, which means that you can’t even develop
autoimmune disease without having a leaky gut. And there’s exposure to
environmental toxins. There’s exposure to food toxins. The
poor-quality Western diet certainly affects the microbiome.
Basically what determines whether someone will manifest autoimmune or
allergies or inflammatory disease is a combination of genetics, the
status of their microbiome, and then the presence of environmental
triggers, like poor diet, stress, sleep deprivation, and environmental
toxins, to name a few.
