Fermented Foods for Gut Health: Myths vs Science

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Kate Scarlata, MPH, RD (00:00):
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Dr. Megan Riehl (00:38):
Hello friends, and welcome to The Gut Health
Podcast, where we talk about allthings related to your gut and
well-being.
We are your hosts.
I'm Dr Megan Riehl, a GIpsychologist.

And I'm Kate Scarlata, a GI dietitian.
I'm super excited for today'stopic and guest.
We will be talking aboutfermented foods for gut health
myths versus science.
Our guest today is EliSaCaffrey.
She's a PhD candidate in theSonnenberg Lab in the Department
of Microbiology and Immunologyat Stanford University School of

(01:11):
Medicine.
Her research explores theinterplay between fermented
foods, microbial communities andhuman health, with a focus on
characterizing the metabolitesproduced during fermentation.
She holds a master's degree inbioinformatics from John Hopkins
University and has priorexperience in biotech research

(01:33):
focusing on gut endocrinology.
Aliza recently co-led theFermentation and Health Speaker
Series with David Zilber and DrJustin Sonnenberg and is the
founder of Rotten Menu, aplatform dedicated to
demystifying fermentationmicrobiology.
She has an excellent paper inAdvances in Nutrition that she

(01:55):
is the lead author on, titledUnpacking Food Fermentation
Clinically Relevant Tools forFermented Food Identification
and identification andconsumption, which reviews the
state of state on foodfermentation metabolites and
health benefits.
We will link this in our shownotes.
Welcome, Elisa.
Thank you so much.

I'm very excited to be here.
I mean fermented foods.
We're going to go beyond justsauerkraut.
I'm going to learn a lot thisepisode and it's always fun to
really dive into different waysthat different things can impact
our gut health.
So, Elisa, we like to startwith a myth buster and, as we
kick things off, what myth wouldyou like to bust pertaining to

(02:38):
fermented foods and gut health?

Elisa Caffrey (02:40):
So I would say that a food that contains
microbes does not mean that itis fermented would be my myth
that I would like to bust, and alot of that comes from the way
in which we see fermented foodsin grocery stores.
Now, when we talk about thingslike gut health and fermented
foods, the landscape has gottenvery confusing.

And so trying to really understand what are
foods that are fermented andwhat are foods that might
contain probiotics and what arefoods that might just have that
people hear, you know, justusing, like sauerkraut.
And we've talked about kimchiand we've talked about some of
the literature around thesefoods and our gut health.
But we're going to dive deeperthis episode and really learn

(03:38):
some of the science and alsojust some key takeaways on what
we're looking for at the grocerystore if we want to explore
this aspect of health Absolutely, and I definitely think there's
just a lot of misconceptions inthis area, so I'm excited to
have an expert that reallyunderstands it.

So let's start with just a very like
elevator pitch about the gutmicrobiome.
What are some of the terms weneed to know when we're thinking
about, what are we looking at?
Are we looking at the type ofmicrobes in there?
Are we looking at what they'remaking, or the metabolome or
metagenomics, or those big termsthat you use probably regularly

(04:18):
?
This will really set our stagetoday for really having a
baseline as we get into thescience of fermented foods.

When we think of the gut microbiome, we're
talking about the microorganismsthat live in the large
intestine, and so that couldinclude largely bacteria, but
also we have fungi, we haveyeast, we have a lot of viruses
in there.
That's been really exciting,and when we are studying the gut
microbiome community, we reallyare interested in what microbes

(04:47):
are present and at whatabundance, and so that's
generally when we're looking atcharacterizing the gut
microbiome.
When people go and get theirgut microbiome tested, that's
what they're looking at ways ofdoing that.
We can do it in kind of abroader view, which is a

(05:07):
technique called 16S ampliconsequencing and that just looks
at a certain region of a genethat is shared between microbes
of the same genus, and the genusis just a way of taxonomically
defining different microbes.
But if we zoom out, the waythat I like to think of what a
genus is, is that dogs, wolves,coyotes are all part of the same
genus.

(05:28):
When we think of a species level, which is what we can do with
other methods like metagenomicsequencing, that is when you
actually get to dogs are part ofone species and wolves are part
of another species, and sowe're able to get at a deeper
understanding of what thesedifferent species actually are
in the gut.
Then there's another level,which is strain level, which has

(05:51):
been kind of the latest, veryexciting way of thinking about
our gut microbiome, and in thatcase we could really compare it
to dog breeds, for example, andthat is microbes that have an
identity of 99.999 percent.
And so that's when we canactually track strains that
might be from a mother to achild or, in the case of

(06:13):
fermented foods, from theenvironment to the cabbage
itself to say what am I actuallyconsuming.
And so we have a lot of kind ofdifferent techniques, but I
think in the you recent years,we've been able to get really
detailed in terms of reallymapping out this very specific
strain, which might producedifferent chemicals compared to
another strain of the samespecies that are closely related

(06:36):
, but it might have a verydifferent impact on health.

So interesting.
It's always helpful to havekind of these metaphors, to take
a concept that you know for allof our listeners.
If you're like okay, wait, I'mfollowing the genus and the
species and the okay, I'm trying.
You know you might have tolisten to this a couple of times
, but it really helps tounderstand a very complex topic.
So the way you just talkedabout this was, I mean, so

(07:03):
eloquent and obviously, like youare the expert in this space
and we don't have to know all ofthe details of what you're
saying, but you're highlightingthat it does take a lot of
thinking through to understandthis.

Totally.
I mean, the way that we reallyhave thought about the gut
microbiome for a while wasreally just based on this kind
of broad genus idea which, ifyou think of it in terms of
coyotes and dogs and wolves allbeing in the same genus, it was
so broad and so now we'refinally able to get to a level.
That's been really, reallyhelpful.
And the other kind of thing is,once we get to the species

(07:41):
level, we can really startlooking at diversity or richness
, which has been a reallyimportant metric for thinking
about the gut microbiome andhealth.
And so, in terms of you know,people have studied a number of
different ways in which we wantto characterize or understand
what a healthy gut is.
But as of now, I think the kindof best metric is that a more

(08:01):
diverse microbiome makes for ahealthier gut, and we really see
that in terms of the way thatpeople might respond to certain
treatments and drugs, that themore diverse your gut is, the
better the response In terms ofrisk of certain diseases.
Again, the more diverse your gutis, the better your response
and the less likely you are tohave certain of these especially

(08:23):
non-communicable diseases.
And what has been reallyexciting about kind of
connecting this back tofermented foods was that there
was a study done a few years agonow that was one of the first
to really show a dietaryintervention, which was a
fermented food diet increasedgut microbiome diversity, which
is something that we reallyhadn't ever been able to do,
where you can change the way inwhich your gut microbiome might

(08:47):
consume, look at certain fibersand produce different
metabolites and have a differentresponse.
But really increasing thediversity hasn't been shown
before, and so when we think ofconsuming food in order to
impact the microbiome, it seemslike fermented foods have been
really successful in having thispositive effect.

So what qualifies as a fermented food or
beverage?
As we think about how do wediversify our gut microbiome,
tell us some of thequalifications of that.

When we think of fermented foods, we really can
abstract it out to.
You have a substrate, whichcould be fiber, like a cabbage
or milk, If you have dairy.
We have the microbes, and thenwe have time, and so what we
really are trying to get at isany sort of food.
Where we have, we're giving themicrobes the food for them to

(09:38):
consume and enough time toproduce some sort of chemical
that might impact flavor.
It's going to impactpreservation of the food and, as
we're understanding, it's goingto impact the health of the
person consuming it, and thereare a number of different foods.
I mean, I don't think there's asingle group around the world
that does not have some sort offood in their diet that is

(10:00):
fermented in some way or,especially if you think of
pre-refrigeration.
Microbes are consuming andhaving an impact on that food in
some way, shape or form, and wecan break this down either by
substrate.
So thinking of things like,again, vegetable ferments we
have kimchi, we have sauerkraut,we have gundruk, we have a ton
of different things Dairy wehave kefir, we have yogurt, we

(10:23):
have cheese.
But even getting to fruit right,Like wine, is technically a
fermented food.
We have vinegar, even justusing sugar.
So for kombucha, we have teaand sugar as kind of a base for
the fermentation.
Meat ferments right, Likecertain types of sausage used to
be fermented.
So we really, I mean you canferment anything right Like, as
long as it's the raw ingredientis accessible to the microbe and

(10:46):
you create an environment forthat microbe to want to consume.
So that could be regulatingtemperature, regulating the
amount of salt.
You can get fermentation tohappen, which you also see a lot
in kind of fine dining now withthe rise of fermentation.
They're trying to ferment, youknow, waste products even in
order to get some really coolflavor profile to come out.

I've seen some top chefs that you know they'll
talk about their fermented foodsthat they'll bring on for a
challenge or something, and Ihear what you're saying.
Yeah, totally.

So I'd like to talk a little bit about
fermented foods.
Everywhere on TikTok,everywhere on social media, it's
like have more fermented foods.
They're a source of probioticsand you know, probiotics has a
specific definition and thisjust can sometimes be the case
that they are, and sometimesmaybe not.

(11:37):
Can you elaborate a little biton fermented foods and are they
all a source of probiotics orwhat do we know?

I'll actually take a step back and just say,
talking about these differentsubstrates, there are different
ways in which you can actuallythen get the microbes to start
the fermentation, or where arethese microbes coming from?
And in certain cases, like invegetable ferments, we have wild
fermentation, which is justmicrobes from the environment
start fermenting and just turnsout work incredibly well to make

(12:07):
some sort of sauerkraut.
We have what's also called likea backslop method, which might
be used a lot in sourdoughproduction, where you have like
an old batch and it's acommunity that's fairly stable,
but we haven't reallycharacterized it and you can put
it in.
And then we have examples, likein yogurt, where we're going to
pasteurize the milk and thenadd in a strain that has been

(12:29):
usually pretty well studied, andthat's an example of a microbe
that is both going to be wellstudied for fermentation but
also for the probiotic potential.
And so probiotics really areaccording to the WHO.
They have a definition they'rethese live microorganisms that
when you administer them inadequate amounts they have some

(12:50):
sort of health benefit, and sothey really have to be well
characterized.
The ISCPP, which is thisinternational research group,
International ScientificAssociation for Probiotics and
Prebiotics, has gone a stepbeyond that and said they also
need to be defined at a strainlevel.
You need to have the genomesequence.
So we really have to deeplycharacterize these microbes in

(13:14):
order to say that they areprobiotics and we also need to
really understand what is thespecific benefit that they're
giving to the host.
And so there's been this kindof split between probiotics that
we have studied and very wellcharacterized and then these
studies looking at consumptionof fermented foods saying we see
a benefit, but most fermentedfoods don't actually have

(13:37):
well-defined probiotic strains.
We just know that there's somebenefit to consuming these
microbes that are established inthese food communities,
basically.
And so the short answer is mostfermented foods are not
probiotic unless there are veryspecific examples.
Usually it's dairy ferments,like some yogurts, some kefir,

(13:58):
and you can usually see that onthe food label when you get it.
But if it's something you'remaking yourself, it does not
technically meet the definitionof a probiotic.
But that doesn't mean thatthere isn't a benefit to it.
And so a lot of that also comesdown to just historically how
we study probiotics.
And there could be potentialprobiotics in fermented foods.
We just haven't characterizedthem yet.

Yeah, I think that's really perfect
explanation and I think whatpeople miss sometimes is that
probiotics need to be alive.
So there are some fermentedfoods that we're baking or
pasteurizing and heating in sothat kills off the microbe and
we can talk a little bit moreabout that.
But just as a reminder,probiotic is live.

(14:44):
That's part of the definition.
So that's one way to kind ofthink about it.
When you're thinking aboutfermented foods, If it's been
pasteurized or baked, unlessyou're adding something after
the fact, there's definitely nota probiotic in there.
But to your point, which is avery important point, that
doesn't mean it's not a healthyfood or maybe really beneficial

(15:06):
to your gut microbiome.
It's just that it's not goingto fit that little definition
right.

Exactly, yeah, okay.
So as a consumer here,sometimes I've had a roller
coaster of an emotionalrelationship with my McDonald's
Coke and right now we'vedivorced and I'm not drinking
soda.
But now we go into the grocerystores and we're seeing
prebiotic soda or the healthieryou know.
Just again, as consumers andI'm one of them that are going

(15:34):
in what are your thoughts onthose types of beverages?
What's the thinking behind that?

Great question.
So these terms become veryconfusing.
We have prebiotics, we haveprobiotics, we now have
postbiotics.
So, to kind of break those down, we can really think of
prebiotics as ingredients thatare there to feed the microbes.
So usually it's some sort offiber that's been added where
you can have some benefit.
The probiotics are these verywell-characterized microbes that

(16:00):
have to be alive.
Probiotics are these verywell-characterized microbes that
have to be alive.
And then postbiotics is thisnew term where basically, if you
have heat killed a probiotic orany microbe that is known to
have some sort of benefit, sopost-pasteurization you would
have technically, thesepostbiotics.
Sometimes people might just addthings like lactic acid, which
is a metabolite produced bymicrobes, to a food and call

(16:23):
that it has this postbiotic.
It gets tricky because in termsof marketing it makes a lot of
sense to say we want to try toreconstruct a food that is going
to be very stable.
So if I have a probiotic sodaaddition, know, addition of
these strains that have thisprobiotic benefit.

(16:43):
But a lot of the work that hasbeen done in fermented foods is
looking at these whole foodsthat are consumed and so you're
missing out on a lot of this.
You know, fermented foods endup being very messy of, like you
know.
We generally know what microbesare in there.
We can look at that, we canknow some of the metabolites and
the chemicals they're producing, but there's a lot we still
don't know about them, and sowhen you start breaking apart

(17:05):
these foods and trying to putthem back in combinations, you
might be missing a lot of thisbenefit.
And we still haven't reallyunderstood.
Do we actually get the samebenefit from deconstructing
these fermented foods andputting them back together in
stable combinations, or is therejust more of a benefit to
leaving some of this diversitythat we would be consuming?

(17:26):
Even in a yogurt that has itsdairy and these well-defined
strains, you still have notfully characterized what the
chemical milieu, the number ofdifferent metabolites in there,
are going to be, and so whenyou're consuming yogurt day to
day, even if you're justconsuming yogurt, there are
going to be differences in whatmetabolites you're exactly

(17:47):
consuming and the levels, andit's still an open question as
to maybe that is.
What is really important isgetting these different amounts
of nutrients and chemicalmetabolites compared to
something that might be verystable and taste very good and
be shelf ready.
You know, shelf stable butmight be missing some of that
important diversity andnutritional value.

I think of fiber, the same, you know.
People always ask, like youknow, what fiber supplement do
you recommend?
And I'm like food first,because there's so much else
there.
Right To your point, you've gotbacteria in this milky
substance and it's a liveexperiment going on and we have
no idea what's being made and weknow some of it.

(18:30):
Obviously there's some acidity,right, there's some flavor
profiles that we can detect, butthere's so much else going on.
It's a little scienceexperiment in a way.

Yeah, I mean I think we see this a lot.
Even I mean I think of again,wine is not the best example
when we really talk aboutfermented foods for a health
benefit, because there still isethanol in there.
But I mean, when you you knowyou have wine, you might open
the same bottle and you mighthave very different flavors.
And that's wine that was madein the same place, it's going to
be aged for the same amount oftime, but just some little

(19:02):
variability in the microbesmight lead to these very
different changes in flavor andflavor.
At the end of the day is ametabolite, and so when we think
of that when it comes to health, you can also really understand
how, yes, opening two differentyogurts might lead to very
different metabolites that we'reconsuming.
Both might be beneficial and wejust don't know.

(19:23):
And so maintaining thatnutritional diversity is going
to be very important.

Yeah, keep trying different things you know
.
And also letting your tastebuds explore the different
things too, because these allcome with lots of different
tastes that you know.
Depending on your culturalbackground, your environment,
you might try something and gowhoa like my tongue is zippy
right now and, I think, alsoletting your kids try different

(19:49):
from as young of an age aspossible, to get them used to
some of this yummy, gut healthfriendly fermentated benefit
food and that's very scientific.
That's my scientificexplanation of that
Non-dietitian here.
Tell us a little bit about thevarious fermentation methods
you've started to tell us, butif you can kind of summarize for

(20:10):
that, describe them for us andalso give us some ideas of which
foods use these methods.

Yeah, there are different ways in which we can
start the fermentation process,but then there are also
different groups of microbesthat are largely used to ferment
.
So I'll see if I can kind ofbreak this down in different
ways.
So, for example, if we'relooking at what we call kind of
wild fermentation, and so thatis really just using microbes
that are in the environment,they could be from your hands,

(20:38):
they could be from your kitchen.
Honestly, there's been a lot ofwork done in this space and
it's still kind of an openmystery of where are the
microbes in your sauerkrautreally coming from?
Where we have a general senseof maybe some of the cabbage,
some on your hands, but actuallytracking where they come from
has been very interesting.
And so in that case what you'redoing is you are cutting the

(21:00):
cabbage, you're exposing some ofthese carbohydrates for the
microbes to start consuming, andso there you end up getting a
lot of lactic acid bacteria, andso these are microbes that
largely produce lactic acid, andso you get a very specific
flavor, and we see this again.
If you're doing any sort ofbrine ferment so let's say
you're making carrots and thenadd 2% salt and water, that is

(21:23):
also lactic acid ferment youcould be doing kimchi as another
example where the microbes comefrom the environment, end up in
your jar fermenting and youhave this lactic acid
fermentation happening.
Lactic acid fermentation is alsoin dairy.
In this case we're not addingthe salt and we might be adding
specific strains, but we seethis in cheese, in yogurt, in

(21:45):
kefir, and so we have kind of anumber of other ferments in the
dairy space where we tend topasteurize the dairy first and
then add in our specific strainof interest.
Then we also have acetic acidfermentation and that's largely
vinegar and kombucha, and so inthat case we have a SCOBY, which

(22:05):
is this symbiotic community ofyeast and bacteria, and in that
case we have exactly both a mixof the yeast and the bacteria
that are used as a starter, andthe actual thickness of the
SCOBY itself is a lot ofcellulose, and so you're able to
kind of passage that where wedon't know the exact strains
that are present.
But we have this fairly stablecommunity and it's fun to kind

(22:28):
of two different people makingkombucha and you compare it.
The flavors are totallydifferent when you make them at
home, but the general ideashould be it's very similar
bacteria and similar yeast.
So that's always fun to kind ofexplore that.
And then we also have yeastfermentation, where we can think
of largely, let's say, insourdough as well, where when

(22:51):
you're making your own sourdoughyou're going to have both
lactic acid bacteria and yeast.
That's present.
But you could be purchasing ayeast strain and adding it in
and that might not be as diversein terms of the microbial
community, but you're stillgetting the yeast that is
fermenting.
And that's very different frombreads that are made with
chemical leaveners, so in thatcase it would not be a fermented
product and of course you alsohave.

(23:12):
Again, I keep going back towinemaking, but wine is made
with yeast as well.

You are in California.

I know.

Napa is right down the road.

Exactly.
And then we finally also havefilamentous fungi, and so that's
when we think of aspergillusoryzae, which helps to make miso
, or rhizopis oryzae, which isto make tempeh, for example, and
so in that case we usually havesome sort of legume the
soybeans that are steamed, andthat helps to kind of sterilize

(23:43):
the environment, and then we'regoing to add in a starter of the
different fungi that we'reinterested in the different
molds, and in that case we'rereally trying to avoid a lot of
bacterial growth and just getthis filamentous fungus to kind
of take over the environment.
And the advantage of thefilamentous fungi is that
they're really, really good atmaking enzymes to break down
certain products, and so theyactually help to break down the

(24:06):
soybean and or, you know, incertain cases rice, and really
make either this kind ofbeautiful savory umami flavor or
the sweet flavor for thingslike amazake, which is a mix of
rice and aspergillus .
So there are so many methodsand there really is if you don't

(24:29):
like sauerkraut.

There's so many other options out there to try.
What would be yourrecommendation of like if this
is brand new to you?
Where might you encouragepeople to start?
And, kate, I'm sure you havelots of opinions on this too.
But what do you think if thefamily isn't really thinking
much about fermented foods?
Where do they go?
First?

I feel like yogurt is always a good place to
start in terms of kind offlavor palette, but I also think
just starting slow and justsmall little bites of sauerkraut
, small little bites of kimchi,I think often, especially when
you have the strong lactic acidflavor, can be very overwhelming
.
But just, I don't know, tryingdifferent things.
The other kind of interestingthing that has been reported in
some of the participants of thedietary interventions that the

(25:09):
Sonnenberg Lab has done incollaboration with Christopher
Gardner's nutrition group hasbeen that they often report that
they might not really likefermented foods to begin with
and then, once they start eatingthem, they start craving them.
And we see that in some of thework where, even after
participants were told you knowyou don't have to eat fermented
foods anymore, you know you cango back to your normal diet,

(25:30):
they still continue to eat themand that they just become
incorporated in their diet, andso the science behind that needs
to be explored.
But I think that's veryexciting.
And so just saying you know,try different things, put them
together, see what you prefer,might open up doors to novel
flavors that might have somesort of benefit as well.

We add sauerkraut to sandwiches and
just do small amounts, anddifferent sauerkraut has
different flavor profiles.
So like trying that and justkind of almost like lettuce on a
sandwich.
You know just a little bit ofit.
It's a little tangy, littlesalty.
You know that's somewhere Imight start and my kids actually
like sauerkraut.
So I think, like everything,the more exposure you have to

(26:20):
these things and with yogurt youknow you can get Fage yogurt
which is very kind of creamy andnot very acidic, and then other
brands that might be have moreof that lactic acid really tang.
So I think even across yogurtsyou can get different flavor
profiles as well.

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Back to sort of the fermentedfood studies, and I know the one
that I believe the one you werequoting on was the fermented
foods versus high fiber diet.
So it was a 40 gram fiber dietversus six servings of fermented

(28:16):
foods and in that study theyused all live containing
fermented foods, so the microbeswere alive.
They weren't using sourdough,for instance, in that particular
study.
So is there advantages ofselecting fermented foods that
have live cultures versus?

(28:37):
I mean, I know, let me justplug my little low FODMAP.
I do a lot with IBS patientsand you know sourdough bread,
when it's slow fermented, isactually tends to be lower.
It can be a little higher inmannitol sometimes but for the
most part lower in thosefructans which are the biggest
culprit for most people, and sothat really affords them to have

(28:59):
that.
So I love sourdough.
That's an advantage and there'sno live bacteria.
But overall, if you had to bezoomed out.
Do we want the live microbesfirst and foremost, or are they
just all great?

in different ways .
That's a great question and hasreally changed, I think, in the
past few years, even in termsof the way we think about it.
When the FeFiFo paper or thestudy, this fiber fermented
study, dietary intervention wasfirst designed.
Fermented study, dietaryintervention was first designed.
A we're kind of we I wasactually not part of that study

(29:32):
at all the group really went inwith just kind of the current
understanding of generalconsensuses eating live microbes
is good, we want raw, wild,fermented foods.
It was designed just trying totest our fermented foods, even
interesting to look at.
Right, it was meant to reallybe a control group for the fiber
arm of the study, and so that'swhy you know there was a

(29:53):
selection towards maintainingkind of live microbes.
But there have been a number ofstudies since then that have
come out that comparepasteurized versus and this has
largely been in sauerkrautspecifically pasteurized versus
unpasteurized and in certaincases.
So there've been three studiesthat kind of come to mind.
The first was in 2018, which isthis Nielsen et al that was

(30:17):
comparing patients with IBS,saying pasteurized versus
non-pasteurized, and they foundthat both had reported kind of
relief from symptoms, and sothey were like, okay, there's no
real difference betweenpasteurized and not pasteurized
for this population, and so thatwas kind of a first indicator
of maybe for people who might bemore sensitive to some of these
foods when they're notpasteurized, having pasteurized

(30:40):
foods might be good.
Another study that is currentlyin bioarchive which is from
someone in the lab, sean Spencer, was looking at differences in
immune cell type, calledregulatory T cells, which are
very important for maintainingimmune homeostasis in the gut,
and he was comparing sauerkrautbrine to filter sterilized

(31:01):
sauerkraut brine, so no microbes, or the kind of brine with the
metabolites in it, and he foundthat there was a similar
increase in these regulatory Tcells, so the cell type really
important for preventinginflammation.
And then this other study thathas come out this year, which
has been very exciting, that wasagain doing this fresh

(31:23):
sauerkraut or this unpasteurizedversus pasteurized, and they
actually did it.
You know this very elegantstudy which is this crossover
study and so where you haveparticipants eating sauerkraut
that is pasteurized and thenhave a four-week washout period
so they stop eating sauerkrautand then switch to either the
pasteurized or the notpasteurized and you have two
groups at the same time that areswapping.

(31:44):
So it's a really good way ofseeing what the actual impact is
of this certain food on thediet, because you have time when
you're consuming it, thenyou're not consuming it anymore,
so you can see what's going onand then you go back to it, and
what they found was thatparticipants that were eating
the pasteurized sauerkrautactually had an increase in
plasma short-chain fatty acids.
And short-chain fatty acids area type of metabolite that's

(32:07):
primarily made by microbes inour gut microbiome that are
known to have, for the most part, a very important benefit for
our immune system, and so theseare kind of just early
indicators that it might be thechemicals themselves that the
microbes are producing thatmight have more of an impact, if
not the same impact, and sowe've been really interested in

(32:29):
exploring this, particularlywith patients where it might not
be recommended for them toconsume fermented foods if
they're live or raw, for example, with immunocompromised
patients, where the idea is wehave this benefit to the actual
fermentation process itself thatthe chemicals microbes are
making are likely having apositive impact on the immune
system, and so if we pasteurizethem and so you're not consuming

(32:54):
the live microbe, you could begetting the same benefit.
And so they're designing someclinical interventions now that
are trying to explore this more,but I would say, as of right
now, if you are a patient whomight be a little sensitive to
consuming fermented foods,consuming the pasteurized
version of that cooking with itis a great way of incorporating

(33:14):
those foods into your diet.
And again, there also are somany different fermented foods
that really finding foods thatyou might not be as sensitive to
is going to be very important.
But for the most part, yeah,our understanding is diversity
is important, so find what worksfor you and if you need to cook
it, pasteurize it.
That sounds great, as long asyou're incorporating some of

(33:35):
that into your diet.

Love it.
Who knew, who knew?
I figured oh, it's got to bethe live, it's got to be the
live, but it's really whatthey're doing in there before we
even eat it.
Exactly.

So cool.
It's very cool and we both do alot of work in the IBS and DGBI
space and I work with a lot ofpatients with inflammatory bowel
disease and both groups ofpeople are at higher risk for
anxiety and depression.
It's kind of thisbi-directional experience and
when we think about variousmultifactorial treatment
opportunities, where is thescience right now in kind of

(34:12):
fermented foods and people'smental health and gut health in
general?

I think that is a prime area for exploration.
There've been a few groups likeJohn Kryan in Ireland has been
doing some really amazing workin that space and exploring that
as we learn more about the gutbrain axis and the way in which
not only does diet impact yourgut microbiome but fermented
foods right, making thesemetabolites that could have a

(34:38):
direct impact on your gut brainaxis and gut health, I think is
really important to continue toexplore.
I think we're still kind of inearly enough stages that it's
hard to make a directrecommendation, but I would say
that I've also just talked topeople that there's one person
specifically I'm thinking of whohas ADHD and during COVID,

(34:59):
started making sourdough and wasjust telling me how making
sourdough grounded them in time,especially during this kind of
COVID time and so part of it too, of like, yes, there's the
benefit of the consumption, butI think there's also benefit to
the practice of fermentationwhere again, kind of connecting
to your food and you know whenyou're having to take care of
something also has this kind ofadded benefit which I think is

(35:22):
very exciting to really think ofwhen it comes to mental health
and, yeah, and kind of wellnessas a whole, that this kind of
reconnection to preparing foodand engaging has this kind of
large benefit and just feelinglike you know you're making
something, that you're, you'reraising these microbes and
you're consuming it, and sothere's also that benefit to it
as well, it just reminds me oflike people that were like

(35:45):
naming their starter and like itbecame such a hobby, and I love
that idea, that concept of youknow you are more thoughtful
about what you're putting in,you're stopping, you're thinking
through the process, there'ssome science, but you're getting
those little zaps of endorphinsthat are great for our mental

(36:06):
health and our well-being.

So maybe not a prescribed treatment for anxiety
or depression yet, but verycool area of research coming
down the pipeline.

Yeah, definitely yeah, I'm like
cooking is my relaxation.
My husband's always like you'vegot a lot going on.
Why are you in the kitchen?
And I find it from a mentalhealth standpoint it is very
relaxing.
So maybe yeah, there'ssomething there, but I do think
it's just like growing your ownfood in a garden.
Right, there's this whole, youknow, like raising a child not

(36:39):
quite, but that it's somethingyou've nurtured and that makes
us feel good.
When we think about fermentedfoods, are there any potential
risks?
I know like kombucha can havealcohol, for instance, and miso
is high salt.
Are there any negatives?
Or patient populationsObviously immunocompromised.

(37:00):
We want to be careful with liveactive cultures, maybe.

Yeah, there are a few kind of key examples.
The first, I would say, arehistamines, so people who are
histamine intolerant, fermentedfoods I don't know if there's
been a kind of a survey acrossall fermented foods to see which
ones might be higher or lowerin histamine, but for the most
part it's understood that thereis histamine production in
fermented foods.

(37:24):
You know, I was actually justsome of the work that I was
recently doing was comparingsauerkraut made with green
cabbage versus red, and thereare differences where the ones
made with red cabbage tends tohave lower amounts of histamine.
But that really has more to dowith how tolerant an individual
is more than kind of the fooditself, cause there's some
people that can eat unlimitedamounts and they're mostly fine.

(37:45):
Individuals who are also onMAOIs so monamine oxidase
inhibitors that's usuallytreatment for depression might
be sensitive to high levels oftyramine, which might also be in
certain fermented foods, likecertain cheeses that are aged
for a long time, and so justbeing more kind of mindful of
that Sodium is kind of a big.

(38:05):
It's honestly a veryinteresting one because, yes,
fermented foods primarily, notjust vegetable ferments where
you have two percent saltusually, but also misos that
could have up to 20 salt.
There's certain studies thathave looked at for, I think,
primarily in mouse and ratmodels of high blood pressure.
They give them miso and theyactually don't see an increase
in blood pressure in these cases, and soo, and they actually

(38:27):
don't see an increase in bloodpressure in these cases.
And so the question is what isgoing on?
Are there other compounds inthere that might be having an
impact?
And the way that we're definingservings right now is just
based on one tablespoon of misois considered a serving, but
maybe for individuals that havehigh blood pressure and need to
watch their sodium intake, asmaller amount might have the

(38:48):
same benefit, but you don't haveas much sodium.
But that is kind of an openarea, and so I think it's I'm a
little hesitant to kind of makeany recommendations, but there's
kind of interesting workhappening there.
But again, there are fermentedfoods that are lower in sodium,
like dairy ferments and some ofthe filamentous fungi tempeh
right will have.
You don't use as much salt inthose to actually produce them,

(39:12):
and so there are kind ofopportunities there to still
incorporate fermented foodswithout having to consume foods
that might be higher in insodium.
And then of course there's, yeah, immunocompromised individuals,
people who are pregnant, wheretechnically they're still in
this kind of gray space whereconsumption of live microbes,
especially in higher abundances,might not be recommended, but

(39:34):
again going to kind ofpasteurized fermented foods and
using those instead With thepregnancy, it's very exciting.
There is the follow-up fromthis FeFiFo study.
There's a study now that'songoing called the MOMS study,
which is a maternal offspringmicrobiota study that is being
written up and should bepublished very soon and that was
comparing pregnant women whoeither were consuming high fiber

(39:58):
, high fermented food both atthe same time or their kind of
normal diet, and so hopefully inthe next year they're going to
be kind of new recommendationsor new indications for what are
the best recommendations forpregnant women when it comes to
fermented foods, and so that I'mvery excited about that.
That study it's.
I'm not a part of it, but I'vejust seen some of the results

(40:19):
and it's very cool.

Very cool.
Cause I remember early you know, following gut microbiome
science and just the differentchanges that women's microbiome
goes throughout the trimestersand there was some signals that,
like in the third trimester,there were some changes that
almost looked like diabeticmicrobiome, so probably some

(40:42):
microbiome way to add weight toyour body or whatever it is that
it's doing.
That's probably protective, butit looked very similar to
individuals with diabetes.

So it'd be interesting to see how we
manipulate our diet and whatthat does, and from a number of
different factors yeah, what Ithink is really exciting about
the study as well is that notonly are they following the
women up to birth, but they'reactually going to follow the
influence up to five years ofage.
And so this is also getting atthe idea of you know, if you're

(41:14):
able to change your gutmicrobiome while you're pregnant
, does that affect what microbesare passed on to your infant?
And if we know this, you knowrelationship between the gut
microbiome diversity and theimmune system, could you
potentially have a lower risk ofhaving your child develop some
of these food intolerances, forexample like peanut allergy?

(41:34):
And what role does having adiverse microbiome during
pregnancy or consuming certaindiets during pregnancy have on
the offspring and kind of yourinfant health?
So the first part of the paperof just looking at the women and
the birth outcomes is going tocome out, I think, in the next
few years and then in five yearstime, once they've followed up
on all these children.

(41:55):
Then, yeah, we'll have kind ofthis longer term follow-up, but
it's very exciting.

You've talked a little bit about the power of
these little active microbes and, rather than just and going
beyond, just identifying them inthe gut, and so can you explain
the importance of the microbialmetabolites like
lipopolysaccharide or LPS, fromgram-negative microbes and how
this is beginning to shift ourunderstanding of gut health?

So LPS, which is it's part of the outer membrane
of gram-negative microbes, andmost fermented foods are not
gram-negative, so we reallyshould not be getting that much
in the fermented foods at all,and in fact, there's been some
kind of early evidence that somefermented foods which are
largely gram-positive, mightactually impact and decrease the

(42:43):
abundance of LPS in your gut.
Your gut also should not behigh in LPS.
Usually, it's a sign thatsomething weird is going on, and
so that tends to be, yeah, notof a lot of concern when it
comes to fermented foods.
But certain things likeshort-chain fatty acids, which
we know, for example, acetateand lactate, are short-chain

(43:04):
fatty acids.
They're made in your body.
They're made in your gutmicrobiome by your gut microbes,
but they're also made by yourmicrobes in sauerkraut and
kombucha, and so there are thesereally interesting parallels
where we have right in our gutmicrobiome.
We're consuming a food, themicrobes make these short-chain
fatty acids and these othermetabolites Aerolactates, for

(43:25):
example, are another kind ofclass of compounds that have
been of interest but when you'reconsuming a fermented food, the
same thing is happening.
You're taking your fiber, you'retaking your dairy, they're
making these compounds and youconsume them and they're going
to be absorbed.
We actually still need tofigure out exactly which
compounds are rapidly absorbedand which ones are degraded,

(43:46):
because, honestly, the gut is ablack box and so it's hard to
figure out exactly what goes onin there.
But understanding what is it infermented foods that might
actually be absorbed and havedifferent impacts on health.
And so we know again that inyour fermented food you're going
to get some of theseshort-chain fatty acids, you're
going to get some of thesearylactates and just kind of a

(44:06):
number of compounds that youmight be able in the future to
personalize, to say, even forjust comparing green and red
sauerkraut, their differencesand what metabolites are
actually being produced.
But maybe we can make amicrobial community that's going
to be really good at making onespecific compound that maybe
you are deficient in and try tosee if we can kind of use that

(44:27):
to target the yeah, kind oftarget your health and make
personalized fermented foods.
And so it's been very excitingand interesting to really
explore this metabolite andchemical space, because I had
gone in assuming, you know, it'sa vegetable ferment, they make
lactic acid, they must make alot of similar stuff, and it
turns out that they don't, thatthere are these kind of you know

(44:50):
, large, really abundantmetabolites, primary metabolites
, like the short chain fattyacids that they do make, that
are similar, but the amount,even of lactic acid, is going to
depend on how long did youferment, what type of substrate.
Different kimchis are going tohave different amounts,
different dairy products aregoing to have different amounts,
and so, getting at, you know,can we standardize these?

(45:12):
Do we want to standardize them?
What is really happening is,yeah, it's very exciting, but
the kind of general takeaway isthat they're diverse.
Diversity does matter, and wejust know that difference in
fermented foods and consumingdifferent fermented foods tends
to have that beneficial effect,and so just keep trying
different things.

I like that.
You know I think about.
So a couple of things I want toask.
So you know, when we talk abouteating fiber, we're feeding the
microbes that already exist inthe gut.
I mean, it's a prebiotic.
That's the role there.
When we're eating fermentedfoods, that's the role there.
When we're eating fermentedfoods, we're adding a bunch of
stuff the metabolites, microbesthat maybe never existed in our

(45:53):
gut.
So just so many potential things, things going on there, which
is really really so exciting,and I'm definitely going to be
upping my fermented food intake.
I'm jazzed about this wholetopic and I feel like I'm pretty
good about it, but I thinkvariety is lacking.
I need to get a little bit moreexploratory with some of these

(46:14):
things.
But for our listeners and again, you've made it very clear that
fermented foods have so manypotential health benefits just
on their own, whether they're asource of probiotic or not.
But for those that areinterested in selecting a
fermented food that is a sourceof a probiotic, what do they
look for?
What does a consumer look forat their local grocery store to

(46:38):
say, oh, this is sauerkraut witha probiotic or this is yogurt
with a probiotic?
Are there tips and tricks forthem when they go to the grocery
store.

Yeah, so I mean in some ways, because these
probiotics have to bewell-characterized.
The advantage is they also haveto be listed on the ingredients
because you're adding them tothe food and so you should be
able to just look at theingredient list and either have
them listed under theingredients or sometimes they
might say contains live activecultures and then has a list of
the different probiotic strains.

(47:09):
Sometimes it gets very tricky toknow whether it's just a kind
of added mixture of definedcommunity and they have the list
, or whether it's actually areally clearly defined probiotic
.
And so usually a probiotic willhave not just the name of the
species but also some sort ofnumber or some sort of letter

(47:31):
after it, and so that could alsohelp you.
If you were interested in kindof tracing where that came from,
what the genome was, what thebenefits are, you can actually
go and kind of find that it doesget very messy in the,
especially in the kind of thefood space, so it does get very
hard to identify some of these.
I mean yogurt I think is thebest example of a food where

(47:51):
usually you look at the back andit will say you know,
streptococcus thermophilus, andthen some sort of number or some
sort of bulgaricus strain, andthen a number behind it.
I mean, yeah, it does get verytricky.

It's a little tricky.
I like when they at least usethe term probiotic.
Maybe that helps a little bitprobiotic yogurt?

No, exactly, although that gets tricky as
well because there's noregulation, at least in the US,
as to how to use these terms.
And so you could go and I'veseen it kind of at farmer's
markets where you know a jar ofsauerkraut will say a probiotic
sauerkraut and it technicallydoes not meet the legal
definition.

But you know, you also want to sell your
product and say it has livemicrobes and so yeah, yeah,
maybe if there's a certainproduct that you really like and
you're curious, I guess youcould go on their website and
learn more specifically about aspecific yogurt or a specific
sauerkraut.

Yeah, but it is a little murky, it is murky, and
I would say for the most part,if someone is actually going out
of their way to purchase aprobiotic and put it in the food
, they will let you know.
So yeah, going to their website, you should be able to figure
it out and they'll have theinformation there.

Perfect.
Yeah, I'm in Michigan andthere's just been a lot of
sickness over the winter, a lotof antibiotics flying around and
I'm just thinking that like aneasy way to help diversify your
gut microbiome after you knowyou've given your kid another
antibiotic for their earinfection.
You know, yogurt is a good one.
I know that it feels easier forus to grab something, and so am

(49:29):
I right on that.
Is that a good way to go?

Great question.
I don't think anyone has donethat specific study saying are
fermented foods a good way ofrestoring the gut after
antibiotic use?

But yeah, I don't know if I want to
speculate too much on it, but itsounds yeah, that's okay, I'm
going to keep doing it.
I don't know, but you don'thave to.

What has been really interesting about the
increase in diversity that wesee following fermented food
consumption is that whenresearchers are actually trying
to identify, you know, the firstquestion would be are these
actually coming from fermentedfoods?
So you see this increase indiversity and most of them are
not.
And so it's also like is thisactually?
It's not like, you know, youeat a yogurt and then suddenly,

(50:15):
or the streptococcusthermophilus from the yogurt
suddenly will integrate intoyour gut.
That's likely not happening.
There must be something aboutthe fermented foods itself.
Maybe again this kind of the mixof metabolites that you're
consuming, I don't know, thelike interaction with microbes
in the food that is eitherleading to an increase in

(50:39):
microbes that are already inyour gut but just below levels
of detection that might be kindof coming up that allows them to
grow better, or it primes yourgut microbiome to be a place
where, I mean, you're exposed tomicrobes all the time, right?
So when you swallow, you'regoing to get some microbes in
there.
When you touch a surface andyou you know, just on the

(50:59):
surface of your food you'regoing to have something, and so
does it just change your gutenvironment to allow it to be a
place where microbes are justmore easily integrated from the
environment into your gut.
We don't know.
And so I think the idea of ifyou take antibiotics and then
you take yogurt, are thosestrains going to be replacing
your gut microbiome?
I don't think so.

(51:20):
I think there likely is stillsome sort of general change
happening to the gut environmentitself as a whole, and that's
kind of again like an openquestion.
But I think it's also very,very exciting in terms of, yeah,
where are these microbes comingfrom and how are we getting a
more diverse gut?
But somehow fermented foods aredoing that and helping.

And you've mentioned, you know in terms of
like how much we can consume orshould consume.
It could be as little as youknow, a few bites to introduce
it, but is there any sciencearound like how much we should
actually try to intake, right?

Now I would say it gets tricky because we still
don't really know how to definea fermented food serving.
So again, with miso, we say onetablespoon, because that's what
was on the container, but maybe, you know, we should really be
thinking about this in terms ofa total number of live microbes
a day, or a total abundance of acertain of like lactic acid or

(52:17):
acetic acid you should beconsuming in a day, and so we
haven't quite been able toidentify that yet as a kind of
where do we see this benefit?
I think that's something thatthis mom study is trying to look
at a little bit, because Ithink a fourth of a cup is one
serving of sauerkraut.
But then you might go and youget these.

(52:38):
You know, a bottle of kombucha,that's two servings, and so if
you drink one you get two, andthere were some participants in
these studies that were havinginsane like based on the like
being like 30 servings offermented foods in a day, which
is a crazy amount and like allof us are kind of like.
What does that mean?
Like, how is that possible?
And a lot of it is just basedon one tablespoon of some

(53:00):
concentrated coconut fermentmight count as a serving and so
you might have multiple and soit's hard to know still kind of
what is a serving size.
But just trying to incorporatewhatever works for you.
And I mean I just like to thinkof it more in terms of how many
times a day did I eat afermented food?

(53:21):
And if I had a shot ofsauerkraut brine and then some
of that sauerkraut, I count thatas two like like you know, two
different things, mixing maybesome kefir and some yogurt.
I think less about volume andmore about just how do I
optimize the different types ofeither microbes or metabolites
that I've consumed in a day thatcome from different microbes,

(53:42):
and so that's kind of been myapproach to it.
But I think we're still alittle too early in terms of
kind of upper level, especiallywhen it comes to even, you know,
patients with IPS or on a lowFODMAP diet that might want to
restrict the number of livemicrobes they're consuming or
might be more sensitive to them.
You know, I think the idea ofjust consuming as much
unpasteurized sauerkraut or youknow whatever might not be a

(54:05):
great idea because you mighthave these, you know, gi effects
and so you know if you can getto a certain level you can get
to two, three servings and youstill feel good, then that's
great, great.

So lots to unpack.
I'm thinking, okay, sauerkrautbrine shots, let's go, let's go
yeah, yeah, exactly.
The other thing is well, I know,in the study with the high
fiber and the fermented foods,there were six servings and they
did break it down.
It was like that quarter of acup of kimchi, for instance.

(54:37):
It sounds like six servings,sounds like a lot, but when you
looked at the serving sizes itdidn't overwhelm me, you know.
But yeah, I think listen toyour body is what I try to say
to my patients that I'm workingwith, with IBS, and if they're
upping, you know, a lot ofsauerkraut or kimchi and they

(54:58):
feel distressed, then to dial itback a little bit, right?
So we always, you know, like towrap up our episodes.
Today this has been fantasticwith you know.
Just a personal take on ourguests you know what they do for
themselves, for their guthealth and wellbeing, and we'd
love you to share something withour audience.

I mean I kind of got at this earlier, but I
really like to think of it asjust how diverse is my fermented
food and fiber intake for theday.
So I mean it honestly turns moreinto a game where I just kind
of you, look at your plate andyou say how many of these things
have some sort of microbialconnection to them?
You know, soy sauce, miso, youknow, maybe I add some

(55:40):
sauerkraut brine into a dressingthat I'm making and just try to
kind of add all those up, youknow, and of course, fiber, of
like how many different types offiber?
And when you really startthinking about it you can get
not only very creative but alsojust makes it fun.
We're like you know what?
I'm just going to throw theseextra seeds on there Cause I
want to get up to five things onmy plate today that are these
things versus just four.

(56:00):
And it just also just makes mebecome much more mindful of what
I'm eating and really kind ofthink through you know, where do
these foods come from?
How are they processed?
It makes it really fun.

It does make it fun.
I'm a big nut and seed queenand I'm adding them to
everything.
But I'm definitely going to getinto the sauerkraut brine
movement and add it to my saladdressings.
But you know, variety isimportant, right?
There's so many, like we'rethinking about the different
types of microbes in differentfermented foods.
There's so many differentpolyphenols and different types
of fiber that is fermented indifferent areas of the colon,

(56:40):
and so, again, variety is thequeen here, absolutely.

Well, huge.
Thank you, Elisa, for coming onour show today and to all of
our listeners, we hope that youwill subscribe, follow and like
The Gut Health Podcast.
Your support means the world.
Friends, thank you for joiningus as we grow this gut health
community.
We hope you enjoyed thisepisode and don't forget to

(57:07):
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.css-14f5ked{margin:0;word-break:break-word;display:-webkit-box;-webkit-box-orient:vertical;box-orient:vertical;-webkit-line-clamp:2;overflow:hidden;}Fermented Foods for Gut Health: Myths vs Science