Our Second Brain The Power of the Microbiome
let’s pretend you’re a guinea pig
not an actual guinea pig but the test
subject in a bold experiment
that if it works could make you a mortal
at the age of 75 you volunteer to have
your brain
transferred to a brand new body and on
the surface
the experiment seems to be a success
you’re conscious you can move the limbs
of your new body
you can smell the formaldehyde in the
lab and your memories are intact
but something is missing and you’re not
quite yourself
could it be that the transfer of your
gray matter
was not enough the truth is
there’s another grayish matter in our
bodies one that resides deep inside our
guts
it’s the gooey muck of microbes that
coats the wall of our intestines
which act like a second brain emerging
studies show that gut microbes can
influence
personality and behavior in astonishing
ways you probably wouldn’t be the same
person without your microbes
scientists refer to this collection of
tiny critters living
on and inside of you as your microbiota
there are trillions of microbes in your
gut alone
bacteria fungi viruses and protozoa
we should not judge these microbes by
their size
collectively they outnumber you there
are slightly more microbes in your body
than human cells making up your body
you’re basically a mobile home to
microbes
and their influence on our home can no
longer be understated
given the enormous quantity of
information they bring into our body
the human genome contains about 25 000
genes
our microbiota adds an estimated 50
million more
we refer to those microbial genes in our
body
as the microbiome as with many
scientific discoveries
we first learned about the importance of
the microbiome
when something went wrong after the
introduction of antibiotics in the 1940s
some people developed what was called a
super infection
marked by massive inflammation of the
gut
and unrelenting diarrhea the culprit is
clostridium difficile
vicious bacteria that are naturally
resistant to most antibiotics
clostridium is usually kept in check by
the friendly bacteria in our gut
but those friendly bacteria are wiped
out by an excess of antibiotics
so intestinal bacteria are kind of like
guardians of the gut
fighting villains that invade our space
but what else might these bacteria be
doing
this question prompted scientists to
produce germ-free rodents
a revolutionary tool that has led to
amazing discoveries
these mice or rats are born without any
microbes
and surprisingly they’re scrawny
and sickly and more anxious than normal
which tells us that the microbiome
contributes to proper development
the immune system even neurochemistry
the next quantum leap was when
scientists took intestinal bacteria from
healthy mice
and put it into germ-free mice
scientists have a less than glamorous
term for this
called fecal transplantation the upshot
is the germ-free mice became healthier
after the gut was reputated with
bacteria from a normal mouse
importantly when these formerly
germ-free mice gave
birth their pups the donor bacteria
which is to say the microbiome is
heritable
in addition to mom’s chromosomes we get
her microbes and the millions of genes
they carry
to understand my enthusiasm for this
subject
here’s some of the most incredible
things the microbiome can do
while we get our first microbes from mom
we get additional ones
from our diet scientists wondered if
different
diets are associated with different
microbiota
so they compared the microbiomes from
kids in an italian city
who ate a western diet to kids who lived
in a village
in burkina faso and ate a
hunter-gatherer diet
the results showed a striking lack of
diversity
in the european microbiome there were
fewer species overall
and some species that disappeared
entirely
when your mother said you are what you
eat she really knew what she was talking
about
the microbiome in obese individuals
shows the same pattern
decreased diversity with a lack of
bacteria that digests
fiber and plant-based foods and an
enrichment of bacteria that thrive on
sugar and fat
could these gut bacteria be sending
signals to the brain
that influence cravings if you have a
gut
full of bacteria that need sugar and fat
to grow
could they be manipulating you into
eating junk food
jeffrey gordon conducted the definitive
experiment
linking gut microbes to the size of the
gut
gordon’s team looked at identical twins
discordant for obesity
which means one of the twins is lean and
the other is obese
how can this be if they have exactly the
same genes in their dna
could the genes in their microbes
possibly affect
appetite to test this wild idea
they fed intestinal bacteria from each
twin
to germ-free mice bacteria from the lean
twin
help that scrawny germ-free mouse
gain a normal amount of weight
remarkably
bacteria from the obese twin cause the
mouse to overeat
and become overweight when you ponder
what you want to eat
be advised the nefarious bacteria may be
driving you to make unhealthy decisions
but you can take back control we have
the power to change our microbiome
through diet and exercise studies show
that diets high in fiber and low in
sugar
promote the growth of beneficial
bacteria
these studies paved the way for many
more microbiome discoveries
with the common thread that organisms
receiving intestinal bacteria
start to take on attributes of their
donor
this could shape the future of medicine
in unprecedented ways
let me tell you about some of the
examples i find most compelling
john kryon showed that gut bacteria from
a depressed
person can make germ-free rats
show symptoms of depression they become
uninterested in treats
don’t socialize with other rats and
won’t try to escape from a
life-threatening situation
such as swimming out of a tub of water
gut bacteria may also fundamentally
alter personality traits
stephen collins showed that a strain of
timid mice
become brave when given intestinal
bacteria from a more adventurous strain
of mice
and the fountain of youth well that
might contain sewage rather than water
as gut microbes from young mice help
aging mice
live longer the microbiome also
affects our immune system our intestinal
microbes co-evolved with us for
millennia
but our modern diet and city life is
profoundly different
than our hunter-gatherer past it’s been
proposed that this abrupt
change in lifestyle has disrupted the
harmonious relationship we’ve had with
our microbes
possibly contributing to the dramatic
rise in autoimmune
and inflammatory disorders we see today
in support of this idea it’s been noted
that people raised on farms
have more diverse intestinal bacteria
that appear to offer protection from
asthma and allergies
these studies suggest that the
composition of our microbiome
is driven by our environment as well as
diet
in the 1980s musician huey lewis sang
that
he wanted a new drug but what he might
really have needed
was new microbes you’re probably aware
certain medications work for some
patients but not others
turns out drugs can be processed
differently
depending on the types of bacteria in
the gut
immunotherapy is a type of treatment for
certain cancers
but it doesn’t work for everyone
scientists were able to make
immunotherapy work
in melanoma patients who weren’t seeing
an effect
simply by giving them intestinal
bacteria from patients
who responded well to the immunotherapy
another new study suggests that the
microbiome can affect motherly love
janelle areas found a particular strain
of bacteria
was able to erase the maternal instinct
in mice
mothers possessing these bacteria
neglected their pups
studies also show that children with
autism often have a microbiome profile
that is distinct
compared to children without the
condition what happens when you put
microbes from an
autistic person into germ-free mice
the mice exhibit some symptoms
resembling autism
they engage in repetitive behaviors and
are less social
i could go on and on but i think you get
the idea
i think the only thing that hasn’t been
tried yet is whether microbes from a
liberal can convert a conservative
and vice versa what you might be
wondering
is how we can use this knowledge to
better our lives
is it possible to reshape or replace our
microbiome
earlier i mentioned the odious
superinfection caused by clostridium
historically clostridium has been very
challenging to treat
but fecal transplantation works 90 of
the time
patients can now take so-called poop
pills or crapsels
containing intestinal microbes from a
healthy donor
and in many cases experience relief
within
hours it’s important to add that fecal
transplants are not currently
recommended to treat
any other medical condition and may have
a dark side
and no one wants to go up that creek
without a paddle
there’s a chance a lethal pathogen could
be transferred to the recipient
and given the links between microbiota
and disease
it may be possible to transfer
undesirable conditions like depression
or weight gain donor material must be
carefully screened
and more research is needed to build
confidence in the safety
and efficacy of this promising procedure
remember your microbiome is a core
component
of a second brain we need to approach
treatments
like a form of neurosurgery nonetheless
many people have already volunteered
themselves to be guinea pigs to
probiotics
pills that contain live bacteria and
yeasts
believe to promote good health research
on probiotics is
extremely complicated which makes
sorting out the hype from the reality
very difficult there are many different
types
and quantities of microbes in probiotics
and how they interact with the body can
be highly individualistic
depending on occur a person’s current
microbiome
depending on their genes and their diet
it is likely that remodeling the
microbiome will have to be tailored to
each individual
like other forms of personalized
medicine
as with vitamin supplements the majority
of studies suggest that probiotics
confer
no obvious benefit to people who are
already healthy
probiotics may relieve some specific
intestinal issues
such as the gi distress caused by
certain antibiotics
but other studies show they actually
impair repopulation of the microbiome
after a course of antibiotics there is
some evidence probiotics help with
irritable bowel syndrome
but not enough for the american
gastroenterological association
to recommend them at this time
some studies have shown that people
taking probiotics
experience elevated mood less anger and
improves sleep
a recent review of seven small studies
supported the idea that probiotics
may help ease depression a bit these are
promising preliminary findings but more
rigorous evidence is needed
to support many of the claims associated
with probiotics
and there may be some downsides some
people experience brain fog
and cramps after taking probiotics
there’s also worry that they could
introduce antibiotic resistance genes
into your system
this is a largely unregulated industry
in the us
which also raises concerns about the
quality control of these products
prebiotics may be the more sensible
choice at this time
prebiotics are foods that contain or
support the types of gut bacteria
we know to be good for us we’re talking
about foods
high in fiber and low in sugar they
include
fermented foods fruits vegetables
beans nuts seeds and unsweetened yogurt
as hippocrates advised let food be thy
medicine
and medicine be thy food the other
sensible thing you can do
is appeal to your government to increase
biomedical research funding
so scientists can better understand how
to harness the power of microbes
to treat disease and promote good health
this could lead to the discovery of
specific bacterial cocktails
that could augment treatments for a wide
variety of medical conditions
i hope you leave this talk knowing that
wherever you go
whatever you do you’re not alone you
carry trillions of microbes that are
partners in life
our microbiome helps shape who we are
and proper care of our microbial
partners will promote well-being
cultivate them
the way you would a garden and you’re
sure to have a healthy harvest