July 31, 2025 • 18 mins
In this episode of Daily Value, we look at the surprising connection between dietary fiber and cognitive health. Fiber isn’t just about digestion - it’s a powerful nutrient influencing your brain through the gut-brain axis. We’ll take a look at new research that reveals how optimal fiber intake may physically enhance and/or help maintain the structure of specific brain regions, important for memory and learning. Learn about the different types of fiber, their unique roles, and practical tips to boost cognitive performance through simple dietary choices.
00:00 Introduction: You Are What You Eat
00:56 The Importance of Dietary Fiber
02:37 Fiber's Impact on Cognitive Function
03:53 New Research on Fiber and Brain Health
07:35 Mechanisms Behind Fiber's Brain Benefits
13:59 Practical Tips for Increasing Fiber Intake
16:30 Conclusion: Fiber for a Sharper Mind
PMID: 38424099
PMID: 40589779
PMID: 33641478
Mark as Played
Transcript
Episode Transcript
Available transcripts are automatically generated. Complete accuracy is not guaranteed.
Speaker 1 (00:00):
You are what you eat.
We've all heard this phrasecountless times.
It's been embedded in our mindssince it first became popular
back in the 1940s.
Usually we take it as a gentlereminder to eat healthy.
But it's deeper than that.
The foods we choose aren't justshaping our bodies, but are
actively changing our brains.
New findings suggest there'sone specific, often overlooked
(00:23):
component in our diet that couldprofoundly impact memory,
attention and even brainstructure itself.
This nutrient is nottechnically needed to survive,
but it's quite possibly the mostimportant non-essential
nutrient for better health.
Today, on Daily Value, we'llexplore how a seemingly simple
dietary choice could hold thekey to clearer thinking and
(00:45):
sharper cognitive performance.
Fiber might seem straightforwardroughage, bran flakes,
something to keep digestionrunning smoothly but dietary
fiber as we know it today didn'teven fully enter the scientific
(01:06):
conversation until the 1950s,and it wasn't until the 1960s
and 70s that thehealth-promoting role of fiber
began to get serious recognition.
Today, dietary fiber is definedinternationally by the Codex
Alimentarius as carbohydratepolymers, essentially long
chains of sugars that resistdigestion in our small
(01:29):
intestines Notably.
Fiber isn't just a singlesubstance.
Instead, it's a diverse classof carbohydrates, each with
unique chemical properties thatdetermine distinct health
outcomes.
For instance, there are viscousfibers like beta-glucans found
in oats.
Viscosity, by the way, refersto a fiber's capacity to expand
(01:50):
when hydrated.
Highly viscous fibers canactively reduce cholesterol.
There are insoluble fibers,such as cellulose from wheat
bran, which are thought to addbulk to stool and aid digestive
transit.
It's important to note that thechemical properties of the
different fiber types determinetheir impact on host health
outcomes.
There are certain fibers termedmicrobial accessible
(02:13):
carbohydrates.
These have a unique propertythey're metabolized by gut
bacteria.
This fermentation drivesrelevant systemic effects
impacting our health well beyonddigestion, compared to up to
90% of fiber from fruits andvegetables, a fact that might
explain some of the nuanceddifferences observed in health
(02:34):
outcomes between dietarypatterns.
While the influence of dietaryfiber on gut and metabolic
health is well documented,researchers have recently turned
their attention to anotheraspect fiber's potential impact
on cognitive function.
Early data, particularly fromanimal studies, strongly
suggests that diets deficient infiber cause significant
(02:55):
cognitive deficits, includingimpaired memory and reduced
synaptic plasticity.
These deficits were accompaniedby increased inflammation in
brain regions necessary forlearning and memory, especially
the hippocampus.
Now, interestingly, althoughprevious human studies hinted
that higher fiber intake isassociated with better mood and
(03:16):
cognitive performance, researchexplicitly examining how dietary
fiber influences brainstructure in humans has been
scarce.
The limited data we do havesuggests that dietary patterns
richer in fiber may beassociated with better overall
brain integrity, includinglarger brain volumes and reduced
white matter damage.
(03:36):
Yet not many previous humanstudies have systematically
explored whether dietary fiberdirectly correlates with
measurable structuraldifferences in specific brain
regions linked to memory,attention and learning.
That all is beginning to change.
A study just published out ofthe University of South Carolina
(03:57):
has finally begun to close thisgap, probing the question of
whether dietary fiber intake canliterally reshape brain areas
involved in cognition and memory.
In other words, can fiber notjust support your gut but
structurally enhance or preserveyour brain?
This was a cross-sectional studythat leveraged advanced
neuroimaging techniques toexplore how fiber intake affects
(04:18):
the brain, specifically lookingat gray matter volume in a
sample of 190 healthy adultsranging from 20 to 79 years old.
Now, measuring gray mattervolume in a sample of 190
healthy adults ranging from 20to 79 years old.
Now, measuring gray mattervolume isn't straightforward, so
researchers used a high-levelneuroimaging method that allowed
the scientists to detect subtlechanges in brain structure,
(04:39):
changes that might seem minor,but could indicate significant
impacts on cognitive health andbrain function.
Seem minor, but could indicatesignificant impacts on cognitive
health and brain function.
Specifically, the studyexamined the hippocampus and the
parahippocampal gyrus, two keyregions embedded deep within our
temporal lobes.
The hippocampus is essentialfor forming new memories and
spatial navigation.
Damage or shrinkage here isstrongly associated with memory
(05:01):
decline, cognitive impairmentand Alzheimer's disease.
The parahippocampal gyrus worksclosely with the hippocampus,
helping process contextualinformation and visual spatial
memory, like recalling locationsor navigating familiar right
parahippocampal gyrus.
Interestingly, they foundassociations between higher
(05:22):
fiber intake and improvedperformance in attention and
language tests, suggestingpotential functional cognitive
benefits beyond structuralintegrity alone.
The researchers took it a stepfurther, looking at whether
there's an optimal level offiber intake for brain health.
They found what researcherssometimes call the Goldilocks
effect, indicating that havingtoo little fiber is detrimental,
(05:44):
but having extremely highlevels may not offer additional
benefits, specifically,participants with at least a
moderate level of fiber intake.
That was an index score around1.74.
According to their calculations, people consuming this much
fiber showed notably higherhippocampal volume compared to
individuals consuming very lowor excessively high fiber
(06:06):
amounts.
Exactly how much fiber is that?
Well, each participant's fiberindex score reflects relative
dietary fiber concentrationacross their diet, not an
absolute amount.
From this study and based onpopulation intake data that's
been corroborated a few timesover.
We're going to go over fiberamount recommendations in just a
little bit.
We can infer that participants'maximum fiber-related neural
(06:31):
protection was occurringsomewhere between 25 to 30 grams
of fiber per day.
In simpler terms, thesefindings suggest that, while
fiber may generally help protectthe hippocampus and supports
cognitive function, there mightbe an ideal sweet spot a certain
level of fiber intake thatprovides maximal cognitive
protection.
Too little might leave yourbrain vulnerable, but
(06:53):
significantly overshooting thisrange might not give you extra
benefits, highlighting theimportance of balanced dietary
intake.
These results build upon prioranimal studies that showed clear
deficits in cognitive functionand hippocampal structure with
fiber deficiency.
It is also in alignment withpast research in humans showing
(07:14):
that fiber intake was tied toimprove cognitive performance,
including faster informationprocessing and better work in
memory.
But this new human data takesit further, demonstrating that
dietary fiber doesn't justcorrelate with better cognition.
It might actually reshape andstructurally protect brain
regions involved in memory andlearning.
So how exactly might fiberexert these protective effects?
(07:35):
Well, that brings us to thenext piece of this puzzle the
gut-brain axis.
Now we've established thatfiber intake correlates with
physical changes in brainregions critical for cognition,
notably the hippocampus.
But how does fiber exert thisinfluence on brain structure and
function?
Well, when we think aboutfiber's effects on cognition,
two broad categories emergeMechanisms that rely on our gut
(07:58):
microbiome and those thatoperate independently of it.
That operate independently ofit as it goes for independent
pathways.
Let's consider that fiber candirectly influence our gut's
lining, what is called theintestinal epithelium.
Fiber interacts with theseintestinal cells known as
enterocytes, triggeringsignaling pathways that include
AMP, activated protein kinase orAMPK, epidermal growth factor
(08:21):
receptors and toll-likereceptors.
Through these pathways, dietaryfiber supports the integrity of
our gut barrier by promotingthe formation of tight junction
proteins and encouraging thegrowth and renewal of gut lining
cells.
Additionally, fiber regulatesthe immune system within the gut
by modulating the release ofsignaling molecules that we call
(08:41):
cytokines and chemokines.
This has been shown to affectimmune cells, including
dendritic cells, macrophages,monocytes and mast cells.
This was first demonstrated inan animal study in which
supplementation with resistantstarch resulted in reduced
macrophage expression in adiposetissue and improved insulin
sensitivity.
Macrophages are specializedimmune cells.
(09:04):
These microbiota independentactions suggest that fiber could
directly maintain gut healthand lower systematic
inflammation, potentiallyprotecting the brain.
Now, perhaps the mostinteresting and likely route
through which fiber communicateswith our brain involves gut
bacteria.
Our microbiota microbesmetabolize dietary fiber,
particularly these forms thatwe've termed as microbial
(09:26):
accessible carbohydrates, intopotent signaling molecules.
Chief among these are shortchain fatty acids like acetate
propionate, especially butyrate.
Short chain fatty acids don'tjust passively float around the
gut.
They actively interact withsystems throughout the entire
body.
For instance, they helpmaintain intestinal and
blood-brain barriers.
(09:47):
Short-chain fatty acidsstrengthen gut barrier integrity
, preventing harmful substancesfrom entering circulation, and
reinforce the blood-brainbarrier by increasing the
expression of proteins likeoccludans.
Short-chain fatty acids canreduce inflammation in the gut
and body by interacting directlywith immune cells.
They also influenceneurotransmitter production,
(10:07):
like serotonin, glutamate andGABA, and enhance neurotrophic
factors such as brain-derivedneurotrophic factor or BDNF.
As most of us know it, one ofthe most interesting mechanisms
involves the vagus nerve, theprimary communication line
linking your gut to your brain.
Fiber-induced short-chain fattyacids and beneficial microbes
(10:29):
can activate vagal pathwaysaffecting memory and emotional
regulation directly.
Gut bacteria and short-chainfatty acids stimulate gut
hormone release Hormones likeglucagon, like peptide 1 or
GLP-1, peptide YY and ghrelin.
These gut-derived hormones cancross the blood-brain barrier or
signal through neural pathwaysinfluencing brain functions
(10:52):
linked to learning and memory.
At first glance, these pathwaysmight seem a little complex or
dizzying, involving everythingfrom immune cells and gut
bacteria to neurotransmittersand hormones, but the message is
reasonably straightforwardDietary fiber impacts cognitive
function, not just because ofwhat it does in the gut, but
because of how those effectsripple outward throughout layers
(11:15):
of biological complexity,eventually reshaping and or
helping maintain brain structureand function.
In simple terms, when we eatfiber, we feed beneficial gut
bacteria.
Those bacteria produceshort-chain fatty acids which
protect our gut lining, reduceinflammation and communicate
with our brains via hormones,nerve signals and other
(11:36):
biochemical pathways.
Over time, these tiny molecularsignals accumulate, possibly
enhancing our mood, attentionand memory and even physically
shaping different brain regions.
Much of the data in humans onthis topic is observational.
However, there was a randomizedplacebo-controlled trial
published just last year thatfurther supports the findings
(11:58):
we've discussed to this point.
This study was called thePROMOTE trial, a study designed
specifically to assess whethertargeting the gut microbiome
could practically enhancecognitive function in older
adults.
What made this trial unique?
Well, the PROMOTE trial used adesign called twin-pair
randomization.
This means they recruited pairsof twins aged 60 and older.
(12:21):
Each twin within a pair wasrandomly assigned either a daily
prebiotic fiber supplement or aplacebo.
Both twins follow the samephysical activity and dietary
regimen, so any observeddifferences could be attributed
with greater confidence to thefiber itself, minimizing genetic
and environmental confounding.
Participants took a dailyprebiotic supplement containing
(12:44):
7.5 grams of prebiotic fiber,specifically a mixture of inulin
and fructooligosaccharides,also known as FOS, in an
(13:06):
approximate 50-50 ratio over thecourse of 12 weeks.
The cognitive results wereclear and after 12 weeks,
participants taking theprebiotic supplement
demonstrated significantimprovements.
In a specific memory testdesigned to measure visual
memory and new learningabilities, skills that are among
the first to decline inconditions like Alzheimer's
(13:28):
disease Improved scoresindicated better memory function
, suggesting that prebioticsupplementation could
potentially play a role insupporting memory retention and
learning, even at an older age.
This trial stands as proof ofconcept, opening doors for
larger, more definitive studies,but the takeaway was promising
(13:49):
Altering your gut microbiotawith fiber-rich prebiotics may
be an effective, accessibleapproach for enhancing brain
function and protectingcognition as we age.
So what does this practicallymean for you?
The reality is most of ussimply aren't getting enough
dietary fiber.
Current guidelines suggestconsuming at least 14 grams of
fiber for every thousandcalories you eat, so for most
(14:11):
adults, that's roughly between28 to 35 grams of fiber per day.
However, the most up-to-datedata suggests that most adults
are only consuming a maximum of17 grams of fiber per day.
When I say most adults, I meanbetween 90 and 95 percent.
The most up-to-date studies onthe matter may even suggest a
need for a higher fiber intakerecommendation to experience
(14:35):
substantial health benefits andcognitive benefits.
Research now points towardshigher targets, maybe even
closer to 50 grams per day,similar to what we see in
populations from rural ornon-industrialized regions,
where cognitive decline andchronic diseases are notably
less common.
But how do we practicallyachieve these fiber goals?
Well, to start, it helps tounderstand that not all fiber is
(14:57):
created equal.
Different types of fiber offerdifferent benefits.
First, there's soluble fiber,which forms a gel-like substance
in the gut and can help managecholesterol and lower blood
sugar levels.
This is the kind of fiber thatis 70 to 90% accessible by gut
microbes.
Good sources of soluble fiberinclude oats, barley beans,
(15:18):
apples, berries, citrus fruits,carrots and psyllium husk.
There's also insoluble fiber,which doesn't dissolve in water
but instead helps move foodthrough your digestive system.
You'll find insoluble fiber inwhole grains like wheat, bran,
nuts, seeds, legumes, potatoesand many green vegetables.
Approximately 30% of thesefibers are accessible to gut
(15:38):
microbes.
Finally, there are more definedprebiotic fibers.
These are especiallyinteresting because they
directly nourish beneficial gutbacteria and help support the
gut-brain connection we've beendiscussing today.
Prebiotics are abundant infoods such as garlic, onions,
leeks, asparagus, bananas,artichokes and so on.
(15:59):
You can also find them assupplements containing inulin or
fructooligosaccharides Again,those are often called FOS.
Fructooligosaccharides Again,those are often called FOS.
These are highly fermentablefibers, which is in part what
makes them so beneficial.
But, on the flip side, somepeople can experience GI
distress with highly fermentablefibers.
The research is still evolving,but one thing is becoming
increasingly clear Targetingdietary fiber intake could be a
(16:23):
promising strategy for promotingbrain health and possibly even
slowing the progression ofneurodegenerative conditions.
While we've seen associationsbetween fiber intake and
improved memory, attention andbrain structure, it's important
to recognize that dietaryinterventions do not act in
isolation.
The benefits observed inhigh-fiber diets may also stem
(16:43):
from other nutrients typicallyfound in those foods Polyphenols
, unsaturated fatty vitamins andantioxidants.
It's nearly impossible toseparate these things completely
, but fiber, especiallyfermentable types like inulin
and pectins.
They stand out for theirability to consistently modulate
the gut microbiota, generateneuroactive metabolites and
(17:04):
influence systemic inflammationand even neurotransmission, and
that's what makes it such aninteresting and accessible
target.
Fiber isn't a supplementreserved for clinical settings.
It's a fundamental component ofeveryday foods.
Small changes to your plate candeliver real physiological
signals to your brain over time.
This doesn't mean that you needto count grams obsessively.
(17:26):
It means thinking about fiberas more than just roughage.
Think of it as a cognitivenutrient, a daily investment in
your long-term mental clarity,memory and resilience.
So whether you're choosing oatsover pastries, adding lentils
to your salad or simplyincluding an extra serving of
vegetables at dinner, thesearen't just gut-healthy choices,
(17:46):
they're brain-smart decisionsas well.
Thank you for joining me todayon Daily Value.
If you found this interestingor useful, share it with someone
who's still underestimatingtheir bowl of beans and berries.
Until then, eat well and staysharp.
You are what you eat.
We've all heard this phrasecountless times.
It's been embedded in our mindssince it first became popular
back in the 1940s.
Usually we take it as a gentlereminder to eat healthy.
But it's deeper than that.
The foods we choose aren't justshaping our bodies, but are
actively changing our brains.
New findings suggest there'sone specific, often overlooked
(00:23):
component in our diet that couldprofoundly impact memory,
attention and even brainstructure itself.
This nutrient is nottechnically needed to survive,
but it's quite possibly the mostimportant non-essential
nutrient for better health.
Today, on Daily Value, we'llexplore how a seemingly simple
dietary choice could hold thekey to clearer thinking and
(00:45):
sharper cognitive performance.
Fiber might seem straightforwardroughage, bran flakes,
something to keep digestionrunning smoothly but dietary
fiber as we know it today didn'teven fully enter the scientific
(01:06):
conversation until the 1950s,and it wasn't until the 1960s
and 70s that thehealth-promoting role of fiber
began to get serious recognition.
Today, dietary fiber is definedinternationally by the Codex
Alimentarius as carbohydratepolymers, essentially long
chains of sugars that resistdigestion in our small
(01:29):
intestines Notably.
Fiber isn't just a singlesubstance.
Instead, it's a diverse classof carbohydrates, each with
unique chemical properties thatdetermine distinct health
outcomes.
For instance, there are viscousfibers like beta-glucans found
in oats.
Viscosity, by the way, refersto a fiber's capacity to expand
(01:50):
when hydrated.
Highly viscous fibers canactively reduce cholesterol.
There are insoluble fibers,such as cellulose from wheat
bran, which are thought to addbulk to stool and aid digestive
transit.
It's important to note that thechemical properties of the
different fiber types determinetheir impact on host health
outcomes.
There are certain fibers termedmicrobial accessible
(02:13):
carbohydrates.
These have a unique propertythey're metabolized by gut
bacteria.
This fermentation drivesrelevant systemic effects
impacting our health well beyonddigestion, compared to up to
90% of fiber from fruits andvegetables, a fact that might
explain some of the nuanceddifferences observed in health
(02:34):
outcomes between dietarypatterns.
While the influence of dietaryfiber on gut and metabolic
health is well documented,researchers have recently turned
their attention to anotheraspect fiber's potential impact
on cognitive function.
Early data, particularly fromanimal studies, strongly
suggests that diets deficient infiber cause significant
(02:55):
cognitive deficits, includingimpaired memory and reduced
synaptic plasticity.
These deficits were accompaniedby increased inflammation in
brain regions necessary forlearning and memory, especially
the hippocampus.
Now, interestingly, althoughprevious human studies hinted
that higher fiber intake isassociated with better mood and
(03:16):
cognitive performance, researchexplicitly examining how dietary
fiber influences brainstructure in humans has been
scarce.
The limited data we do havesuggests that dietary patterns
richer in fiber may beassociated with better overall
brain integrity, includinglarger brain volumes and reduced
white matter damage.
(03:36):
Yet not many previous humanstudies have systematically
explored whether dietary fiberdirectly correlates with
measurable structuraldifferences in specific brain
regions linked to memory,attention and learning.
That all is beginning to change.
A study just published out ofthe University of South Carolina
(03:57):
has finally begun to close thisgap, probing the question of
whether dietary fiber intake canliterally reshape brain areas
involved in cognition and memory.
In other words, can fiber notjust support your gut but
structurally enhance or preserveyour brain?
This was a cross-sectional studythat leveraged advanced
neuroimaging techniques toexplore how fiber intake affects
(04:18):
the brain, specifically lookingat gray matter volume in a
sample of 190 healthy adultsranging from 20 to 79 years old.
Now, measuring gray mattervolume in a sample of 190
healthy adults ranging from 20to 79 years old.
Now, measuring gray mattervolume isn't straightforward, so
researchers used a high-levelneuroimaging method that allowed
the scientists to detect subtlechanges in brain structure,
(04:39):
changes that might seem minor,but could indicate significant
impacts on cognitive health andbrain function.
Seem minor, but could indicatesignificant impacts on cognitive
health and brain function.
Specifically, the studyexamined the hippocampus and the
parahippocampal gyrus, two keyregions embedded deep within our
temporal lobes.
The hippocampus is essentialfor forming new memories and
spatial navigation.
Damage or shrinkage here isstrongly associated with memory
(05:01):
decline, cognitive impairmentand Alzheimer's disease.
The parahippocampal gyrus worksclosely with the hippocampus,
helping process contextualinformation and visual spatial
memory, like recalling locationsor navigating familiar right
parahippocampal gyrus.
Interestingly, they foundassociations between higher
(05:22):
fiber intake and improvedperformance in attention and
language tests, suggestingpotential functional cognitive
benefits beyond structuralintegrity alone.
The researchers took it a stepfurther, looking at whether
there's an optimal level offiber intake for brain health.
They found what researcherssometimes call the Goldilocks
effect, indicating that havingtoo little fiber is detrimental,
(05:44):
but having extremely highlevels may not offer additional
benefits, specifically,participants with at least a
moderate level of fiber intake.
That was an index score around1.74.
According to their calculations, people consuming this much
fiber showed notably higherhippocampal volume compared to
individuals consuming very lowor excessively high fiber
(06:06):
amounts.
Exactly how much fiber is that?
Well, each participant's fiberindex score reflects relative
dietary fiber concentrationacross their diet, not an
absolute amount.
From this study and based onpopulation intake data that's
been corroborated a few timesover.
We're going to go over fiberamount recommendations in just a
little bit.
We can infer that participants'maximum fiber-related neural
(06:31):
protection was occurringsomewhere between 25 to 30 grams
of fiber per day.
In simpler terms, thesefindings suggest that, while
fiber may generally help protectthe hippocampus and supports
cognitive function, there mightbe an ideal sweet spot a certain
level of fiber intake thatprovides maximal cognitive
protection.
Too little might leave yourbrain vulnerable, but
(06:53):
significantly overshooting thisrange might not give you extra
benefits, highlighting theimportance of balanced dietary
intake.
These results build upon prioranimal studies that showed clear
deficits in cognitive functionand hippocampal structure with
fiber deficiency.
It is also in alignment withpast research in humans showing
(07:14):
that fiber intake was tied toimprove cognitive performance,
including faster informationprocessing and better work in
memory.
But this new human data takesit further, demonstrating that
dietary fiber doesn't justcorrelate with better cognition.
It might actually reshape andstructurally protect brain
regions involved in memory andlearning.
So how exactly might fiberexert these protective effects?
(07:35):
Well, that brings us to thenext piece of this puzzle the
gut-brain axis.
Now we've established thatfiber intake correlates with
physical changes in brainregions critical for cognition,
notably the hippocampus.
But how does fiber exert thisinfluence on brain structure and
function?
Well, when we think aboutfiber's effects on cognition,
two broad categories emergeMechanisms that rely on our gut
(07:58):
microbiome and those thatoperate independently of it.
That operate independently ofit as it goes for independent
pathways.
Let's consider that fiber candirectly influence our gut's
lining, what is called theintestinal epithelium.
Fiber interacts with theseintestinal cells known as
enterocytes, triggeringsignaling pathways that include
AMP, activated protein kinase orAMPK, epidermal growth factor
(08:21):
receptors and toll-likereceptors.
Through these pathways, dietaryfiber supports the integrity of
our gut barrier by promotingthe formation of tight junction
proteins and encouraging thegrowth and renewal of gut lining
cells.
Additionally, fiber regulatesthe immune system within the gut
by modulating the release ofsignaling molecules that we call
(08:41):
cytokines and chemokines.
This has been shown to affectimmune cells, including
dendritic cells, macrophages,monocytes and mast cells.
This was first demonstrated inan animal study in which
supplementation with resistantstarch resulted in reduced
macrophage expression in adiposetissue and improved insulin
sensitivity.
Macrophages are specializedimmune cells.
(09:04):
These microbiota independentactions suggest that fiber could
directly maintain gut healthand lower systematic
inflammation, potentiallyprotecting the brain.
Now, perhaps the mostinteresting and likely route
through which fiber communicateswith our brain involves gut
bacteria.
Our microbiota microbesmetabolize dietary fiber,
particularly these forms thatwe've termed as microbial
(09:26):
accessible carbohydrates, intopotent signaling molecules.
Chief among these are shortchain fatty acids like acetate
propionate, especially butyrate.
Short chain fatty acids don'tjust passively float around the
gut.
They actively interact withsystems throughout the entire
body.
For instance, they helpmaintain intestinal and
blood-brain barriers.
(09:47):
Short-chain fatty acidsstrengthen gut barrier integrity
, preventing harmful substancesfrom entering circulation, and
reinforce the blood-brainbarrier by increasing the
expression of proteins likeoccludans.
Short-chain fatty acids canreduce inflammation in the gut
and body by interacting directlywith immune cells.
They also influenceneurotransmitter production,
(10:07):
like serotonin, glutamate andGABA, and enhance neurotrophic
factors such as brain-derivedneurotrophic factor or BDNF.
As most of us know it, one ofthe most interesting mechanisms
involves the vagus nerve, theprimary communication line
linking your gut to your brain.
Fiber-induced short-chain fattyacids and beneficial microbes
(10:29):
can activate vagal pathwaysaffecting memory and emotional
regulation directly.
Gut bacteria and short-chainfatty acids stimulate gut
hormone release Hormones likeglucagon, like peptide 1 or
GLP-1, peptide YY and ghrelin.
These gut-derived hormones cancross the blood-brain barrier or
signal through neural pathwaysinfluencing brain functions
(10:52):
linked to learning and memory.
At first glance, these pathwaysmight seem a little complex or
dizzying, involving everythingfrom immune cells and gut
bacteria to neurotransmittersand hormones, but the message is
reasonably straightforwardDietary fiber impacts cognitive
function, not just because ofwhat it does in the gut, but
because of how those effectsripple outward throughout layers
(11:15):
of biological complexity,eventually reshaping and or
helping maintain brain structureand function.
In simple terms, when we eatfiber, we feed beneficial gut
bacteria.
Those bacteria produceshort-chain fatty acids which
protect our gut lining, reduceinflammation and communicate
with our brains via hormones,nerve signals and other
(11:36):
biochemical pathways.
Over time, these tiny molecularsignals accumulate, possibly
enhancing our mood, attentionand memory and even physically
shaping different brain regions.
Much of the data in humans onthis topic is observational.
However, there was a randomizedplacebo-controlled trial
published just last year thatfurther supports the findings
(11:58):
we've discussed to this point.
This study was called thePROMOTE trial, a study designed
specifically to assess whethertargeting the gut microbiome
could practically enhancecognitive function in older
adults.
What made this trial unique?
Well, the PROMOTE trial used adesign called twin-pair
randomization.
This means they recruited pairsof twins aged 60 and older.
(12:21):
Each twin within a pair wasrandomly assigned either a daily
prebiotic fiber supplement or aplacebo.
Both twins follow the samephysical activity and dietary
regimen, so any observeddifferences could be attributed
with greater confidence to thefiber itself, minimizing genetic
and environmental confounding.
Participants took a dailyprebiotic supplement containing
(12:44):
7.5 grams of prebiotic fiber,specifically a mixture of inulin
and fructooligosaccharides,also known as FOS, in an
(13:06):
approximate 50-50 ratio over thecourse of 12 weeks.
The cognitive results wereclear and after 12 weeks,
participants taking theprebiotic supplement
demonstrated significantimprovements.
In a specific memory testdesigned to measure visual
memory and new learningabilities, skills that are among
the first to decline inconditions like Alzheimer's
(13:28):
disease Improved scoresindicated better memory function
, suggesting that prebioticsupplementation could
potentially play a role insupporting memory retention and
learning, even at an older age.
This trial stands as proof ofconcept, opening doors for
larger, more definitive studies,but the takeaway was promising
(13:49):
Altering your gut microbiotawith fiber-rich prebiotics may
be an effective, accessibleapproach for enhancing brain
function and protectingcognition as we age.
So what does this practicallymean for you?
The reality is most of ussimply aren't getting enough
dietary fiber.
Current guidelines suggestconsuming at least 14 grams of
fiber for every thousandcalories you eat, so for most
(14:11):
adults, that's roughly between28 to 35 grams of fiber per day.
However, the most up-to-datedata suggests that most adults
are only consuming a maximum of17 grams of fiber per day.
When I say most adults, I meanbetween 90 and 95 percent.
The most up-to-date studies onthe matter may even suggest a
need for a higher fiber intakerecommendation to experience
(14:35):
substantial health benefits andcognitive benefits.
Research now points towardshigher targets, maybe even
closer to 50 grams per day,similar to what we see in
populations from rural ornon-industrialized regions,
where cognitive decline andchronic diseases are notably
less common.
But how do we practicallyachieve these fiber goals?
Well, to start, it helps tounderstand that not all fiber is
(14:57):
created equal.
Different types of fiber offerdifferent benefits.
First, there's soluble fiber,which forms a gel-like substance
in the gut and can help managecholesterol and lower blood
sugar levels.
This is the kind of fiber thatis 70 to 90% accessible by gut
microbes.
Good sources of soluble fiberinclude oats, barley beans,
(15:18):
apples, berries, citrus fruits,carrots and psyllium husk.
There's also insoluble fiber,which doesn't dissolve in water
but instead helps move foodthrough your digestive system.
You'll find insoluble fiber inwhole grains like wheat, bran,
nuts, seeds, legumes, potatoesand many green vegetables.
Approximately 30% of thesefibers are accessible to gut
(15:38):
microbes.
Finally, there are more definedprebiotic fibers.
These are especiallyinteresting because they
directly nourish beneficial gutbacteria and help support the
gut-brain connection we've beendiscussing today.
Prebiotics are abundant infoods such as garlic, onions,
leeks, asparagus, bananas,artichokes and so on.
(15:59):
You can also find them assupplements containing inulin or
fructooligosaccharides Again,those are often called FOS.
Fructooligosaccharides Again,those are often called FOS.
These are highly fermentablefibers, which is in part what
makes them so beneficial.
But, on the flip side, somepeople can experience GI
distress with highly fermentablefibers.
The research is still evolving,but one thing is becoming
increasingly clear Targetingdietary fiber intake could be a
(16:23):
promising strategy for promotingbrain health and possibly even
slowing the progression ofneurodegenerative conditions.
While we've seen associationsbetween fiber intake and
improved memory, attention andbrain structure, it's important
to recognize that dietaryinterventions do not act in
isolation.
The benefits observed inhigh-fiber diets may also stem
(16:43):
from other nutrients typicallyfound in those foods Polyphenols
, unsaturated fatty vitamins andantioxidants.
It's nearly impossible toseparate these things completely
, but fiber, especiallyfermentable types like inulin
and pectins.
They stand out for theirability to consistently modulate
the gut microbiota, generateneuroactive metabolites and
(17:04):
influence systemic inflammationand even neurotransmission, and
that's what makes it such aninteresting and accessible
target.
Fiber isn't a supplementreserved for clinical settings.
It's a fundamental component ofeveryday foods.
Small changes to your plate candeliver real physiological
signals to your brain over time.
This doesn't mean that you needto count grams obsessively.
(17:26):
It means thinking about fiberas more than just roughage.
Think of it as a cognitivenutrient, a daily investment in
your long-term mental clarity,memory and resilience.
So whether you're choosing oatsover pastries, adding lentils
to your salad or simplyincluding an extra serving of
vegetables at dinner, thesearen't just gut-healthy choices,
(17:46):
they're brain-smart decisionsas well.
Thank you for joining me todayon Daily Value.
If you found this interestingor useful, share it with someone
who's still underestimatingtheir bowl of beans and berries.
Until then, eat well and staysharp.
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