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