Welcome to Huberman Lab Essentials,

where we revisit past episodes for the

most potent and actionable science-based

tools for mental health, physical

health, and performance.

I'm Andrew Huberman and I'm a professor

of neurobiology and opthalmology at

Stanford School of Medicine. And now for

my discussion with Dr. Justin

Sonnenberg. Justin, thanks so much for

being here.

>> Great to be here.

>> I am a true novice when it comes to the

microbiome. So, I'd like to start off

with a really basic question, which is

what is the microbiome?

>> I think, you know, just to start off

with clarifying terminology, microbiome

and microbiota quite often are used to

refer to our microbial community

interchangeably. And I'll probably

switch between those two terms today.

The other important thing to realize is

that these microbes are um not just in

our gut, but they're all over our body.

They're in our nose. They're in our

mouths. They're on our skin. Basically

anywhere that the environment can get to

uh in our body, which includes inside

our digestive tract, of course, is, you

know, colonized with with microbes. And

the vast majority of these are in our

distal gut and in our colon. And so this

is the gut microbiota or gut microbiome.

And um the density of this community is

astounding. You start off with a zoomed

out view and you see something that

looks like, you know, fecal material,

the digest inside the the gut and you

zoom in and you start to, you know, get

to the microscopic level and see the

microbes. They are just packed, you

know, side to side, end to end. It's a

super dense bacterial community almost

like a um bofilm to the point where it's

thought that, you know, around 30% of

fecal matter is microbes, 30 to 50%. So,

you know, it's um it's an incredibly

dense microbial community. We're talking

of um you know, uh trillions of

microbial cells. And all those microbial

cells, if you start to get to know them

and and see who they are, um break out

in the gut probably to um hundreds to a

thousand species. Most of these are

bacteria. Um but there are a lot of

other life forms there. There are archa

which are little microbes that are

bacteria-like but they're they're

different. Um there are uh ukarotes. So

you know we commonly think of ukarotes

in the gut as um as you know something

like uh a parasite but um there are

ukarotes, there are fungi, there are

also little viruses. There are these

bacteria phages that infect bacterial

cells. And so um and and those actually

outnumber the bacteria like 10 to one.

So they're just everywhere there. They

kill bacteria. Um and so there there's

these really interesting predator prey

interactions. But um overall it's just

this really dense, complex, dynamic

ecosystem.

>> Our microbiota seen in newborns. Um in

other words, where do they come from?

And dare I ask, um what direction do

they enter the body? Um there have been

some studies that have looked at um

whether there are microbes in the womb

and and microbes colon colonizing the

fetus and there's some debate about this

but overall it looks like that's not a

big part of the equation of microbial

colonization and um so each time an

infant is born it's this new ecosystem.

It's like an island rising up out of the

ocean that has no species on it and

suddenly there's this like land brush

for you know this open territory. There

also are a lot of different trajectories

that developmental process can take

because our microbiota is so malleable

and so plastic and those trajectories

can be affected by all sorts of factors

in early life. So an example is whether

an infant is born by C-section or born

vaginally. Infants that are born by

C-section actually have a um gut

microbiota that looks more like human

skin than it does like either the vag

the birth canal, the the vagina

microbiota or um the mother's um stool

microbiota. Compound on top of that

whether you're breastfed or formulafed,

whether your family has a pet or doesn't

have a pet, whether you're exposed to

antibiotics. Um there are all these

factors that really can change that

developmental process and really change

your microbial identity eventually in

life. We know from animal studies that

depending upon the microbes that you get

early in life, you can send the immune

system or metabolism of an organism or

other parts of their biology in totally

different developmental trajectory. So,

what microbes you're colonized with

early in life can really change your

biology.

>> How do I know if my microbiome is

healthy or unhealthy?

>> Context matters a lot. What's healthy

for one person or one population may not

be healthy for another person or

population. And I will say that there's

no single answer to this, but there are

some really important considerations.

Perhaps the best way to start talking

about this is to go back to um the

inception of the human microbiome

project, which was this um program that

that NIH started. They invested a lot of

money in 2008 2009 for um really uh

propelling the um field of of gut

microbiome research. It was um becoming

evident at that point that this was not

just a curiosity of human biology that

it was probably really important for our

health. Through those studies, we really

started to get the image that there is

this tremendous individuality in the gut

microbiome. And um and so it's it's

really hard to um start drawing um you

know conclusions after initial pass of

that project of what is a healthy

microbiome. But the other thing that we

started to realize at the same time,

there were studies going on documenting

the gut microbiome of um traditional

populations of humans, hunter gatherers,

uh rural agricultural populations. And

um those studies were really

mind-blowing from the perspective of,

you know, all these people are healthy.

They're living very different lifestyles

and their microbiome doesn't look

anything like a healthy American

microbiome. And so one possibility is

that in the industrialized world we have

a a different microbiome from

traditional populations and that

microbiome is well adapted to our

current lifestyle and therefore healthy

in the context of an industrialized

society. And there probably are elements

of that that are true. Um but another

possibility is that this is a microbiome

that's gone off the rails that it is um

you know deteriorating in the face of

antibiotic use and um uh all the um

problems associated with a um

industrialized diet, western diet um and

that even though the human microbiome um

project documented the microbiome of

healthy people, healthy Americans, that

what they really may have been

documenting there is a perturb herbed

microbiota that's uh really predisposing

people to a variety of inflammatory and

metabolic diseases. If my gut microbiome

was um disbiotic, it was off um early in

life, can I rescue that through proper

conditions and exercise or is there some

sort of um fixed pattern that's going to

be hard for me to escape from? Yeah, the

there's a big field that's emerging now

that um you know we refer to as kind of

reprogramming the gut microbiome. And

the issue that I think we're seeing in

the field is that uh microbiomes quite

often whether they're diseased or

healthy exist in stable states. they

kind of tend towards this um well that

has gravity to it in in a way biological

gravity where um it's really hard to

dislodge that community from that state.

So even individuals for instance that

get antibiotics

um you know you uh take oral antibiotics

the community takes this huge hit. We

know that a bunch of microbes die the

composition changes and you know that

represents a period of vulnerability

where pathogens can come in and take

over and cause disease. But if that

doesn't happen the microbiota kind of

works its way back to something that is

not exactly like but similar to the

pre-anibiotic treatment. Uh we know with

dietary perturbations um quite often

you'll see a really rapid change to the

gut microbiome and then this it's almost

like a memory where it snaps back to

this something that's very similar to

the original state even though the diet

remains different. And so there's this

incredible res what we refer to as

resilience of the gut microbiome and and

um resistance to change or at least

resistance to establishing a new stable

state. So that doesn't mean it's

hopeless to change an unhealthy

microbiome to a a healthy microbiome.

But it does mean that we need to think

carefully about um you know

restructuring these communities in ways

where we can achieve a new stable state

that will resist the microbial community

getting pulled back to that original

state. And you know, one of the kind of

simplest and nicest examples um of this

is a an experiment that um we performed

uh with with mice where we you know,

we're feeding mice a normal mouse diet.

Um a lot of nutrients there for the gut

microbiota, things like dietary fiber

and um we switch those mice, half the

mice to a low- fiber diet. And we were

basically asking the question that, you

know, if you switch to kind of a

westernike diet, a low- fiber, higher

fat diet, what happens to the gut

microbiota? And we saw the microbiota

change. It lost diversity. It was very

similar to what we see in um in the

difference between industrialized and

traditional populations. But when we

brought back a healthy diet, a lot of

the microbes returned. You know, it was

fairly, you know, there there was this

kind of memory where it went back to

very similar to its original state. The

difference is that when we put the mice

on a low- fiber, high-fat diet and then

kept them on that for multiple

generations,

um, we saw this progressive

deterioration over the course of

generations where by the fourth

generation, the gut microbiome was a,

you know, a fraction of what it

originally was. Let's say 30% of the

species only remained um, something like

70% of the species had gone extinct or

appeared to have gone extinct. we then

put those mice back onto a high-fiber

diet and we didn't see recovery. So, in

that case, it's um a situation where a

new stable state has been achieved. Um

in that case, it's probably because

those mice don't actually have access to

the microbes that they've lost. And we

actually know that we did a the control

experiment of mice on a high fiber diet

for four generations. They maintain all

their microbes. If we take those fourth

generation mice with all the diversity

and do a fecal transplant into the mice

that had lost their microbes but had

been returned to a high fiber diet, all

of the diversity was reconstituted. So

it was um you know so your your question

of like how do we establish new stable

states? How do we get back to a healthy

microbiota if we have taken a lot of

antibiotics or have a deteriorated

microbiota? It's probably a combination

of having access to the right microbes

and we can talk about what that access

looks like. It may look like

therapeutics in the future. There are a

lot of companies working on creating

cocktails of healthy microbes, but it'll

be a combination of access to the right

microbes and um nourishing those

microbes with the the proper diet.

>> What's the idea about cleanses and

fasting as it relates to the health or

the disbiosis of the microbiota? Yeah, I

mean we know that like you know in

studies that are being done now to

reprogram the gut microbiota to install

a completely new microbial community,

the first step is to wash away the

resident microbial community that's

there. So if you're in the process of

acquiring a really good microbiota and

you know how to do that, then the the

flushing everything out is great. Um

otherwise what is happening is you're

kind of leaving rebuilding of the

community to chance. Like what is it?

And so, um, you know, what what microbes

are going to colonize, who's going to

take up space after you do this flush or

cleanse. And, um, you know, that I think

it's a a little bit like playing Russian

roulette. You may end up with a a good

microbial community in there afterwards.

You may not. Um, you certainly want to

pay close attention to what you're

eating while you're doing the

reconstitution of the community after

you do something like that. It sounds to

me that avoiding processed foods is a

good idea or heavily processed foods in

general. And I mean, not that you know,

the occasional consumption is is um

necessarily bad, but consuming processed

foods is just bad for the microbiome.

Can we say that categorically?

>> For sure. Okay, you're exactly right.

And we can break down, you know, there's

a lot of data of why different

components of processed food are so bad

for us and so bad for our microbiome.

And I can talk about a few examples of

that. But the flip side of this, the

plant-based diet, if you're eating a

bunch of complex um, you know, fibers

that feed your gut microbiota, your gut

microbiota produces these substances

called short- chain fatty acids, things

like butyrate. And it's known that these

short- chain fatty acids play really

essential components both in terms of

fueling colonocytes, enforcing the

barrier, keeping inflammation low,

regulating the immune system, regulating

metabolism. your gut microbiota is just

producing this vast array of

fermentation endproducts that then get

absorbed into our bloodstream and have

all of these tremendous cascading

effects that appear to be largely

beneficial on our biology. Now processed

foods I think is this other dimension

where you have all of these weird

chemicals, artificial sweeteners, weird

fats, um you know a lot of refined

simple nutrients. the simple nutrients

we've talked about, but we know that for

instance, artificial sweeteners can have

a massive negative impact on the gut

microbiome and can lead us towards

metabolic syndrome. Actually, there's

been beautiful work out of the Whitesman

Institute on this. And then emulsifiers,

these compounds that are put in

processed foods to help them maintain

shelf stability so things don't separate

and so um you know all the the moisture

content is retained appropriately. Um

many of these are known to disrupt the

mucous layer and as soon as you start

disrupting that barrier that can lead

you in the direction of inflammation and

in animal models we know that can lead

towards metabolic syndrome as well. So

there's there's components of processed

food that are when studied in isolation

known to have a direct negative impact

on gut biology and the microbiota.

>> I do want to make sure that we

distinguish uh artificial sweeteners

from non-caloric plant-based sweeteners.

Do we know anything about plant-based

non caloric sweeteners or low caloric

sweeteners?

>> Very little. You know, a lot of those

have um a lot more bang for the buck.

They're they're incredibly sweet. So, it

takes a really small amount for them to

trigger a huge amount of sweetness. And

so it's depending upon the mechanism of

action by which these um sweeteners that

are not sugar are impacting our biology.

It may be that those are actually um you

know less negative or or more healthy

than um the ones that are artificial

just because it requires less of them in

the food for us to perceive that sweet

taste. Um historically there are I think

traditional populations that use these

for instance to sweeten um you know

sweeten different foods um that our

bodies just kind of know how to deal

with those compounds better than the

ones that are synthetic. Um but I think

the you know the studies still need to

be done.

>> Do you actively avoid artificial

sweeteners sucralose aspartame

saccharine you personally? Yeah, you

know, I do I I avoid them, but I'm not I

you know, I think that just doing things

in moderation makes it a lot easier and

doing things slowly makes it a lot

easier. And so so there are very few

rules that I have that are hard and

fast. I'm I'm a pretty flexible eater. I

don't believe that having an artificial,

you know, having a diet coke um will,

you know, somehow cascade into some

terrible disease or something like that.

I'd love to talk about fiber and

fermented foods because you and Chris

had a what I think is a really

interesting and exciting paper comparing

inflammatory markers of people who ate a

certain amount of fiber or certain

amount of of these fermented foods. Let

me take before I dive into that study,

let me take a step back because I think

the reason that we did this study goes

back to this kind of epiphany that we we

had while studying the gut microbiome

because I think when we started studying

it at Stanford, we were thinking about

it as this kind of newly appreciated

aspect of our biology almost like um

finding an organ that we didn't know was

there and starting to think about like

all the drug targets that were there.

Can we go in with small molecule drugs

and think of ways to manipulate this

community to amilarate disease? And um

this is largely the mindset of western

medicine and largely born out of the era

of infectious disease. um you wait for

an infection to start, a bacterial

infection, you treat with antibiotics

and you know that's the way medicine is

practiced. And that's become less

successful over time as we've moved into

this era of inflammatory western

diseases and largely moved out of the

era of infectious diseases, at least

infectious bacterial diseases. that this

paradigm of waiting for diseases to

appear and come into the clinic um is

not really very effective in the context

of inflammatory western diseases,

autoimmune diseases, metabolic syndrome,

uh heart diseases and inflammatory

disease. You know, the list goes on and

on. And so we started to think a lot

about like how can we get out in front

of this? How can we think about like

preventative ways of dealing with this

crisis of metabolic and inflammatory

diseases? And this tremendous beautiful

body of literature started to come

forward in the field that showed that

the gut microbiome is absolutely

critical to modulating our immune

status. So if you change the microbiome,

you can fundamentally change how the

immune system operates. And we know that

the immune system is the at the basis of

a lot of these diseases, inflammatory,

chronic diseases. And so it it brought

up this possibility that maybe the fact

that we're not nourishing this community

well enough, maybe the fact that it's um

deteriorated over time um due to all of

the things that go along with an

industrialized lifestyle, antibiotics

and so forth. Um, maybe we have a

microbiome right now in the

industrialized world that is setting our

immune system at a set point, simmering

inflammation that's driving us towards

these inflammatory diseases. And

wouldn't it be wonderful if we could

figure out how to um uh use diet

specifically, but just kind of learn the

rules of how to reconfigure both the

composition and function of our gut

microbiome so that inflammation was

different in our bodies so that each one

of us was less likely to go on and to

develop an inflammatory disease. Our

flagship study, we wanted to understand

if we put people on a high-fiber diet um

how would that affect their microbiome

and immune system? And if we put them on

a high fermented food diet, a diet rich

in live microbes and all the metabolites

that um are present from fermentation in

foods, how would that change microbiome

and immune system? The idea was in the

case of the high-fiber diet, just

increasing plant-based fiber. So, can

you eat more whole grains, more legumes,

more vegetables, nuts? Get the fiber up

in the range of, you know, from 15 to 20

grams per day up to over 40 grams per

day. So, can you kind of double or more

the amount of fiber that you eat per

day? the people that were eating the

high fermented food uh diet um they were

instructed to basically eat um you know

foods that you could buy at a grocery

store that were naturally fermented and

contain live microbes. Yogurt, kefir, uh

sauerkraut, kimchi. We instructed people

to eat nonsweetened yogurts. Um, a huge

pitfall in this area is you can have a

yogurt loaded with bacteria, kind of the

base of what's healthy, and then a ton

of like artificial flavoring and sugar

loaded on top of that. Manufacturers put

a ton of sugar in after the fact to kind

of mask the sour taste of fermented

foods, which is hard for some people to

become accustomed to. Getting used to

that sour flavor is is difficult, but

people really should try to stay away

from those um fermented foods that are

loaded with sugar. And that's what we

instructed people in this study. A lot

of people shy away from the high quality

fermented foods because they can be

quite costly. Um, I'll just refer people

to a resource in Tim Ferrris's book, The

Four Hour Chef. He actually gives an

excellent recipe for making your own

sauerkraut, which basically um involves

cabbage and water and salt, but you have

to do it properly because you can grow

some um not necessarily uh lethal, but

some somewhat dangerous bacteria if you

don't scrape off the top layer properly.

But he gives beautiful instructions for

how to do this in vats. You can make

large amounts of truly fermented

sauerkraut just from cabbage, water, and

salt. If you're willing to follow the

protocol, you know, if you can get your

hands on a scobby, kombucha is another

one that's super simple. It's

>> you can grow your own.

>> You can you can just make your own and

it's super easy to do. I make it. I

constantly have a batch of kombucha

going at home. And it's just, you know,

it's this it's a scobby, a symbiotic

community of bacterian yeast that you,

you know, you brew tea, you add sugar to

it, and you put the scobby in and you

wait a week or two depending upon the

temperature and you then you just, you

know, move the scobby over to a new

batch and you you're old. You what the

scobby was in is kombucha and it's it's

wonderful.

>> So, how much fermented food were they

consuming in servings, ounces? um how

many times a day, early day, late day.

>> The general instructions were for people

to eat as much fermented foods as

possible. More is better. People um

during the height of the intervention

phase were up over six servings on

average per day of fermented foods. So,

kind of two servings at each meal. And

the, you know, ounces or weight or size,

it really depended on what the fermented

food was. And we just told them to stick

to what was a recommended dose on the

the package that they were they were

buying. You know, for kombucha, it' be

like a six to eight ounce glass um

sauerkraut, like a half cup or something

like that. And same with yogurt. The the

big signal really was in the fermented

food group. We saw all the things that

you would hope to see in a western

microbiota and western human. We saw

this increase in microbiota diversity

over the course of the six weeks while

they were consuming the fermented foods.

We can't always say that um higher

diversity is better when it comes to our

microbial communities. We know there are

cases for instance bacterial vaginosis

where higher diversity is actually

indicative of a disease state. Um but we

um know in the context of the gut and

for people living in the industrialized

world, higher diversity is generally

better. Um we know that there's a

spectrum of diversity. People with

higher diversity generally are health

healthier. If you can push your

diversity higher, you're in better

shape. And so we saw that increase in

diversity and then the major question is

what happened to the immune system as

these people were increasing their gut

microbiota diversity through the

fermented foods. Um we so we did the um

this massive immune profiling and we see

you know a couple dozen immune markers

inflammatory markers decrease over the

course of the study. So we multi we u

measure these at multiple time points

throughout the course of the study and

there's kind of this se step-wise

reduction in things like interlucan 6

and um you know interlucan 12 a variety

of kind of famous inflammatory mediators

um and then even if you go into the

immune cells and you start looking at

their signaling cascades we see that

those signaling cascades are less

activated at the end of the study

compared to the beginning of the study

indicating an attenuation of

inflammation. So, so kind of exactly

what we would hypothesize would lead to

less propensity for inflammatory disease

over time. That's a a huge extension of

a very short study.

>> But did people say they were feeling

better um in any way? And if so, what

did you observe? And again, we're

highlighting these as an data.

>> You know, tons of people say they have

more energy, they think more clearly,

they sleep better. And it's really hard

to uncouple like is this because you

know these people have taken charge now

of what they're eating and just feel

better in general for being in control

of kind of what they're doing or is

there this cascading um set of effects

that are actually kind of emanating from

the gut brain axis and and I should say

you know the the list of this goes on

and on. There are people who claim that

their complexion improves and that their

you know allergies and there's probably

all sorts of ripple effects if you can

affect your inflammation. you c we know

that you can affect your cognition. We

know that you can affect your you know

your your skin and and inflammation

that's occurring on your skin. So so I

really think that there is a basis for a

lot of those anecdotes. It may just be

hard to see in a short study and in um a

small you know a small cohort of people

over a short period of time. you know,

we also have a um a standardized um uh

stool measure that people use and there

was um you know, kind of less

constipation, better bowel movements

over the course of both of these

interventions. So, it did seem like

bowel habits improved, which um a lot of

times can lead to better moods, but that

we weren't able to to measure that.

>> What sorts of interesting things did you

observe in the fiber group? data seem to

be telling us that if you start off with

a diverse microbiota, maybe one that's

better equipped to degrade a wide

variety of of dietary fiber, you're more

likely to respond positively to it. If

you have a very depleted gut microbiome,

you're not as likely to be able to

respond to it. And thinking back to that

experiment that we talked about before

with the multigenerational loss of of

fiber fermenting microbes in in mice

that were fed a western diet. Um it it

may be that many of us in the

industrialized world have a microbiome

that's so depleted now that even if we

consume a high fiber diet at least for a

short period of time we don't have the

right microbes in our gut to degrade

that fiber. And this has actually been

observed by other groups. beautiful

study out of University of Minnesota

looking at immigrants coming to the

United States and you know within 9

months but certainly over the course of

years immigrants that come here lose um

a lot of the diversity in their gut

microbiome but a lot of the fiber

degrading capacity in their gut

microbiome too. So it could be that over

time this becomes a one-way street and

it's hard for us to recover um the the

microbes that that actually can degrade

the fiber. And I think that this

probably intersects with sanitation in

our environment and the fact that we

don't have access to new microbes that

might help us degrade the fiber that we

actually um you know have lost these

microbes and they're in some ways

irreoverable without deliberate

reintroduction of fiber degrading

microbes.

>> Well, you have children. Did you do you

encourage them to uh interact with pets

and dirt and

>> absolutely stuff in the environment

provided that stuff wasn't immediately

toxic?

>> Yeah, exactly. Certainly just with

infectious diseases in general, it's

really important to be aware of um you

know the the possibility for

compromising your health through the

spread of germs. And so that that is

just you know handashing is important

and we have to be careful with you know

um the the spread of germs. But I do

think that um you know the sanitation

sanitization of our environment um has

gone overboard with the you know um

various things being impregnated with

antibiotics you know shopping carts and

things like that and toothbrushes and

you know it's it's like antibiotics and

and um you know things for killing

microbes are are everywhere. And when we

were raising, you know, when our

daughters were young and we were we were

making these decisions, the calculations

that we would make were really um one uh

how likely are they to encounter a

disease-causing microbe? If we've been

out, you know, on a hike or in our

garden, you know, just kind of working

in the dirt or whatever, maybe it's not

as important to wash your hands before

you have lunch, even if there's a little

bit of dirt on them. um if they've been

in a public playground where maybe

there's um other kids with germs or

maybe even chemicals like pesticides and

and herbicides that are being used um

maybe it's more important than to wash

your hands. You know, certainly if

you've been in the grocery store or on

the subway, probably a good idea to wash

your hands, but I so I think you really

need to think about kind of the the

context of it. And um exposure to

microbes uh from the environment is

likely an important part of um educating

our immune system and keeping the proper

balance in our immune system and it's

just a matter of figuring out the right

way to do that safely.

>> What what's the thought about probiotics

for for the typical person that's not

recovering from a round of antibiotics

or that um has been prescribed them?

>> The So I think the the first thing to

say is buyer beware because it's a

supplement market. It's largely

unregulated and that means that there

are a lot of bad products out there and

a lot of products that um even though

they're not intended to be bad, just

don't have great quality control. There

have been several studies that have

taken off the uh over-the-counter just

kind of off-the-shelf probiotics,

surveyed what's in there based on

sequencing, and shown that they what is

in there does not match what's on the

label. So there there are places that

probiotic companies can send their

product to have it independently

validated. So you want to look for that

sort of validation on on a product. Um

there also are names that are just very

wellknown and um you know it's uh

you know their reputations are on the

line. So they probably invest a little

bit more in quality control than maybe

some of the other lesserk known names

because there's such a huge range of

products and because each person is

their own little caper when it comes to

the microbiome. It's really hard to know

um whether there are great products for

a given indication. And the really good

advice that I've heard is try to find a

study that supports in, you know, a

really well-designed study. And this is

very hard for people who aren't

scientists to evaluate, but so, you

know, if you're experiencing a medical

problem or want to consult a doctor, um,

the, you know, that that might be

helpful. But finding a study where a

specific probiotic has successfully done

whatever it is you're looking for and

then sticking with that probiotic is

really the best recipe for as a as a

place to start in this space, I think.

>> And what about prebiotics? Because there

are a number of um reasons why I can

imagine that prebiotics would be

beneficial.

>> The studies that have been done on

prebiotics, the it's really kind of a a

mixed bag of results. The um there have

been studies done with um purified

fibers where you actually see microbiota

diversity plummet over the course of the

study because um you get a very specific

bloom in a small number of bacteria that

are good at using that one type of fiber

and that's at the expense of all the

other microbes that are in the gut. And

so, um, so it's really hard to replicate

with purified fiber what you'd get, for

instance, at a salad bar in terms of the

array of complex carbohydrates that you

would be exposing your microbiota to.

And I think the kind of um uh

broad view of this in the field is that

consuming a broad variety of plants is

and and all the the diverse fiber that

comes with that is probably better in

fostering diversity in your microbiota

than purified fibers. Now, there are um

again a lot of people who benefit from

purified fibers either for GI motility

um or or for other aspects of of GI

health problems that they've been

experiencing. Again, I think it's the

type of thing where you have to um try

to find the thing that that's right for

you. But there um there also are studies

that suggest that if you layer rapidly

fermentable

um fibers on top of a western diet, you

actually can um result in in weird

metabolism happening in your liver

because you have this incredibly rapid

fermentation of fiber along with a lot

of fat um coming into the system. At

least that's the that's the theory. And

in a mouse study that was published a

few years ago, they actually see that a

subset of the mice develop

hepaticellular carcinoma when they're

fed a a highdose prebiotic liver cancer

on top of a um on top of a western diet.

So whether that's representative of

human biology, we don't know. But um you

know purified fibers are definitely very

different um both in terms of the

diversity of structures but also in

terms of how rapidly they're fermented

in the gut because um you know if you

are eating plants the complex structures

there really slow the microbes down in

terms of fermentation and you end up

with a slow rate of fermentation over

the length of your colon as opposed to

this big burst of fermentation that can

happen if you eat something that is

highly soluble and and easily accessed

by the microbes.

>> So, you've covered a tremendous amount

of information and I'm incredibly

grateful. Where can people find out more

about the work that you're doing? Uh, we

can certainly provide links and you have

a book on this topic. So, could you tell

us about the book where we can f learn

more about the Sonnenberg lab and the

work that you're doing? Um, maybe people

will even try and enroll in some of

these studies.

>> Um, yeah. So, uh, Erica, my wife and I

wrote a book called The Good Gut. And um

that that really was a um response to

how we were changing our lives in

response to to being in the field being

very familiar with the research seeing

that a lot of our friends that weren't

studying the gut microbiome but were

very wellinformed many of them

scientists were not doing the same

things we were doing and it was very

clear that it was just the um lack of

information funneling out of the field

to other people. And so we wanted to um

make that accessible to people who are

not microbiome scientists. And then you

know in terms of kind of connecting with

our research certainly there's the

center for human microbiome studies at

Stanford which is kind of our home base

for doing a lot of these dietary

interventions. We list the studies there

um give more information on what we're

doing and then we have a lab website too

that people can go to and read more

about our research and we're always

looking for participants for our

studies. Thank you so much for your time

and for the work you do and I hope we

can do it again.

>> Thanks Andrew. This was a great

conversation.

>> Terrific.