Dietary Supplement Practicum 2018–Emerging Science: The Microbiome and Nutrition

>>Barbara Sorkin: I’m Barbara
Sorkin from Office of Dietary Supplements and it’s my great pleasure
this morning to introduce the first speaker.
First, my Office of Dietary Supplements colleague,
Dr. Cindy Davis. Cindy received her Bachelor of
Science from Cornell University and her PhD in Nutrition
from the University of Wisconsin Madison with a minor
in Human Cancer Biology. She did post-doctoral
training at NCI — and then returned later to NCI and came to the Office
of Dietary Supplements from there. She directs our grants
and extramural activities at the Office of Dietary
Supplements.>>Cindy Davis: Well, great. Thank you very much
for that very kind introduction. It’s my pleasure
to be here today. What I’d like to do
is talk a little bit about the relationship
between diet, the microbiome, and health. So, what I’d like to do is give
a little bit of background on what is the microbiome? What is the evidence
that diet can influence the microbiome
and conversely, how can the microbiome influence
the response to dietary components?
And, interwoven throughout this, is what is the relationship
between diet, the microbiome,
and disease risk? So, humans actually, have been
considered superorganisms and that’s because
we’re a composite of many
different species. In addition to our human or
mammalian or eukaryotic cells, there are also bacterial, viral,
archaeal cells, fungi, phage — and, in fact,
there are estimates that there are anywhere
between equal numbers to up to ten times more
microbial cells than humans. The most recent
estimate suggests that there are 1.3 bacterial
cells for every human cell, but that isn’t considering
the phage, the fungi,
and other microbes. When we talk about
the microbiota, we’re talking about the microbes
in a specific niche. So, the gut microbiota
are the microbes in our gastrointestinal tract, and in fact, that’s about
100 trillion organisms. When we talk
about the microbiome, we’re talking about
their collective genome and in fact,
there are about 100 times as many genes for microbes
as there are human genes. You might also hear
the term metagenome and that’s a combination
of both the microbial and the human genes
or metagenomics and that’s the study
of both the microbial and human genes together. So, what do microbes do for us? Well they have
many important functions. They provide the ability
to harvest nutrients. They produce additional energy otherwise inaccessible
to the host and that’s mainly through
the fermentation of soluble fiber
to the short chain fatty acids: acetate, butyrate,
and propionate. They produce vitamins
such as folate, biotin, and vitamin K.
They metabolize carcinogens, such as heterocyclic amines,
formed in food during cooking. They prevent colonizations
by pathogens and they assist
in the development of a mature immune system. In the limit of time,
I’m only going to talk about the relationship
between the microbes and diet. So, what is the evidence
that suggests that diet can influence
microbial profiles? Well, the first evidence
came from looking at the microbial composition in
globally distinct populations — and I’ll show the landmark
study in the next slide. But there’s also evidence
to suggest that long-term food
pattern consumption, can influence
the microbial composition and this has led
to the term enterotypes and it’s the idea that people
that eat similar diets have similar
microbial composition, regardless of where they live,
their age, their gender. And the two main enterotypes
are the bacteroides enterotype which is in people that eat
a lot of protein and fat and the prevotella genotype which is in people
that eat a lot of dietary fiber. The other source of evidence, is from short-term
intervention studies, including low verses
high fiber diets, animal verses plant
food sources, and macronutrient ratios. So, this is a landmark study
that was first published, suggesting that there’s
a relationship between what people consume
and their microbial composition. In this study they compared
the microbial composition in children from Africa
with those in Italy. As you can see, in Africa, the main microbes
are bacteroides — particularly prevotella
and zyota bacter. In contrast, in Europe
the product children, the predominates are firmicutes.
Why this is actually important, is the two main bacteroidetes,
prevotella and zyota bacter, actually have specific
enzymes present in them that allow them to
hydrolyze cellulose and xylan, which allows them to actually
extract as much energy as possible
from the very high fiber diet that these children consume. So, since they have
a very low intake of energy, it can maximize
the amount of energy that they can get
from their diet. There’s also evidence
from short term feeding study. In this study, ten humans
in a crossover design, were fed either a plant-based
diet or an animal-based diet. Now, I realize this is
a very complicated slide, so I’ll quickly walk you
through the highlights. The plant-based diet
is shown in green. The animal-based diet
is shown in red. And, their feces were collected
for four days and analyzed. This is probably the most
important part of the figure — where they look at the
similarity and differences in microbial composition
among the different individuals, among the different days. And, what I’d like
to highlight is, you notice, that all the red,
tend to come together and that all the green,
tend to come together, suggesting that diet
is actually more important and that when they’re on
these extreme diets — that the microbial
composition changes and that it’s more similar. So, as I said,
the short-term feeding alters
microbial community structure and it overwhelms
inter-individual differences in gene expression, and in fact, it modifies
specific metabolic pathways. This idea that diet
dominates host genotype in shaping
the gut microbiota, has also been shown
in a number of animal studies. I don’t usually go
from the human studies to the animal studies, but the human study
was actually published first. And, in this study,
they compared five inbred and more than 200 outbred
mouse strains, that were fed either a high fat,
high sugar diet or a low-fat, high fiber diet and they looked
at the microbial composition. The results are shown here in this principal
component analysis that looks at similarities
between different samples. You can see, that all the mice,
when they were fed the high fat, high sugar diet clump together
and all those, when they were fed the low fat,
high fiber clump together. And, this was specifically due
to an increase in bacteroidetes when they were on the low-fat,
high fiber diet and an increase firmicutes when they were on
the high sugar, high fat diet. So, how can we use
this information? What type of
dietary modifications can we do to influence
the microbial composition? Well, the first,
is use of probiotics and these are foods
or dietary supplements that contain live bacteria — usually lactobacillus
or bifida bacteria; prebiotics, which are
non-digestible food ingredients which can selectively stimulate
the growth of gut bacteria. Examples include, inulin,
other oligosaccharides, lactulose, resistant starch, and in fact a number
of dietary fibers have also been shown
to exert a prebiotic effect. A symbiotic is a combination
of a probiotic with a prebiotic, and the idea is, that the prebiotic
would actually be a food source or an energy source,
for the probiotic. And, in fact,
other dietary factors can also influence
microbial composition. Microbes are actually,
able to metabolize a lot of the polyphenols
present in tea, cocoa, and wine and use those
as an energy source. And, many spices,
are actually antimicrobial and that’s why they’ve been
used for centuries in food preservation; because, they actually
inhibit the growth of many different microbes. So, I mentioned probiotics. The World Health Organization
defines probiotics as live microorganisms, that when administered
in adequate amounts, confer a health benefit
on the host. The key parts in
the definition of probiotics, are live, adequate amounts,
and health benefit. These include
everything from food, to dietary supplements,
to prescription drugs — and examples of typical
probiotics include lactobacillus and bifida bacterium, but actually yeast
is often sold as a probiotic, and other bacteria
such as E.coli and bacillus. We often think of E.coli
as being pathogenic, but it actually depends
on the specific strain and there are large differences and there are actually some that
are being sold as probiotics. Fermented food
and beverages typically do not contain live cultures
due to the heat treatment, filtration, or food processing
to improve shelf-life; hence, they are
not true probiotics. Examples include
sourdough bread, fermented meat, sauerkraut,
wine and beer, and vinegar. Fermented dairy products
include yogurts, natural cheese,
buttermilk, kefir, and again, these may or may not
be considered probiotic — and whether they are, would depend on
the bacteria levels when eaten and whether the bacteria
have been shown to confer health benefits. Another important source
of probiotics is dietary supplements. Many dietary
supplement probiotics contain more than one billion
live cells per gram and, in fact, many contain
upward of ten billion live cells per gram. And, they’re probably better in
terms of their efficaciousness if they have multiple
strains of bacteria. This is data from
the Nutrition Business Journal, which looks at the sales
of dietary supplements in the United States — and this is data
published in 2017 which looks at sales in 2016.
That year, probiotics, were the third
most popular dietary supplement. Sales were greater than
1.8 billion dollars per year and it increased over 17 percent
between 2015 and 2016. In fact, there are many proposed
health benefits of probiotics because they, potentially, can normalize the intestinal
microbiota composition — this can lead to colonization
resistance and suppression of both endogenous
and exogenous pathogens. It can control
irritable bowel syndrome, inflammatory bowel diseases,
and allergy symptoms — and, they also have
metabolic effects which can affect
colon cancer risk, lactose tolerance,
and serum cholesterol levels. So, what is the evidence
to really suggest that probiotics
do have these health effects? I’m going to utilize one
meta-analysis to kind of show, what are the strengths
and weakness of some of the science
out there, related to probiotics?
And, I chose this one, because it was published —
only — about two months ago. In this study,
they looked at studies that looked at the relationship
between probiotics and BMI. They identified 13 subjects — and when they summarized
the data, they found that individuals
that consumed probiotics, compared to those that didn’t,
had a .27 decrease in BMI and this was
statistically significant. So, of course, the headline is “Probiotics Are Beneficial
For Your Weight.” I want to point out
though, that — there’s inconsistency
in the studies. As you can see,
some are on the left side and others are statistically
significant on the right side. And, I also want
to put it in perspective. Most of the studies
are of short duration — they’re small sample size
and they’re actually underpower to actually look
at the relationship. Even more important — they utilized
different probiotics. Probiotics vary depending
on the bacteria that’s being studied —
or if it even is a bacteria. And, in fact, they also vary
in terms of the matrix they use, the doses they use.
We can go on and on. Most of the trials
are not pre-registered. But, perhaps
the most important point, is that this effect
is not clinically significant. I said that there was a change
in BMI of .27; however, if they actually limit
the studies to only those individuals that were either obese
or overweight to begin with, they found that
the change was halved. So, there was only
a change in BMI of .14. I don’t think
anyone would think, that that’s a really
important change. So, where is the science
related to probiotics? There is preliminary evidence
that some probiotics are helpful preventing diarrhea caused by infections
and antibiotics and improving symptoms
of irritable bowel disease; however, the US FDA
has not approved any probiotics, for preventing or treating
any health problem. Probiotic supplements should
contain at least one billion live cells per gram
and are probably better if there are multiple
strains of bacteria. If people are generally healthy, probiotics do have
a good safety record; however, there have been
reports linking probiotics to severe health effects, such as dangerous infections
in people with weakened immune systems.
What we don’t know, is which probiotics are helpful
and which are not — not all probiotics
have the same effect and the effects are
likely strain specific — how much of the probiotic
people should take, and who would most likely
benefit from taking probiotics. To be honest,
whether a probiotic is beneficial
for a specific individual, probably depends on their background
microbiota composition; however, this is something that’s usually
not taken into effect. As I said, there’s also
evidence that suggests, that many different
dietary polyphenols can influence
the microbiota consumption. This was some studies
that I was involved in — where we looked at
the bacterial abundance after consumption
of cocoa flavanols and we found that in pigs given the highest dose
of cocoa flavanols, there was
a significant increase in the amount
of bifida bacterium in their feces and lactobacillus
in their colon. Well, it’s easy to say —
your microbes changed, but the question is — does it have
a biological effect? And, we actually saw,
that cocoa powder consumption, decreased the expression
of 10 alfalfa and TLR-like receptors 2, 4,
and 9 gene expression, showing that it was
actually having an anti-inflammatory effect. Well, I’ve mentioned,
how various dietary components can influence the number
and types of microbes; however, this is
a two-sided relationship and I’d like to switch gears now
and talk about the relationship of how the specific microbes
that are present can influence the response
to dietary components. Bacteria can produce
new compounds from a number
of food components. A few of the dietary components that are metabolized
by gut microbes and their metabolites
are shown here. In the limit of time,
I’ll only focus on the top two dietary fiber —
choline and carnitine — but I should say, often times,
these microbial metabolites, are more biologically active
than the parent compound. So, one of the dietary
components that has been linked with health effects
is dietary fiber. Dietary fiber
has been associated with a decreased risk
of colon cancer. When the American Institute
of Cancer Research and the World Cancer
Research Fund summarized
the epidemiologic evidence related to dietary
fiber and cancer, they found that
for every ten-gram intake in dietary fiber per day,
there was a ten percent decrease in the risk
of developing colon cancer. Moreover,
this effect was, linear. Dietary fibers are fermented
by colonic bacteria to form short
chain fatty acids, including butyrate, acetate,
and propionate. Butyrate is
the most widely studied and the preferred energy source
of colonocytes, and in fact,
it has differential effects in normal verses cancer cells, which I’ll show
on the next slide. So, this cartoon shows
the relationship between dietary fiber
and colon cancer. Dietary fiber can be divided
into both soluble and insoluble dietary fiber. Insoluble fiber
actually increases the colonic transit time, so there’s less time
for carcinogens to be in contact
with the colonic cells. In contrast,
soluble fibers ferment into short chain fatty acid, the most important
of which is butyrate. In normal cells, butyrate serves
as an energy source. So, the colonocytesutilize it and actually
increase proliferation because of its effects
on energy — and it also increases
differentiation. In contrast, in cancer cells, they undergo something called
the Warburg Effect and what this means
is they actually start utilizing glucose as
a preferred energy source. So, since they’re already
utilizing the glucose for energy,
it means that the butyrate can affect other molecular
targets within the cell. And, the most important
molecular target is HDAC or Histone
deacetylase activity. What it actually does,
is inhibits HDAC, which leads
to decrease proliferation and increase apoptosis. There’s also the evidence
that suggests that dietary fiber
can affect bacterial diversity. It was found that when mice
were fed a high fat diet — excuse me,
a high fiber diet — there’s a large amount
of bacterial diversity. If they’re maintained
on this high fiber diet for multiple generations, they maintain
that bacterial diversity. In contrast, if they’re switched
to a low fiber diet, there’s a decrease in microbial
diversity and over generations there’s a further and further
reduction in diversity. If they’re switched
to a high fiber diet from the low fiber diet, there is some recovery,
but not complete recovery, suggesting that you’re actually
having extinction of certain microbial species.
Well, why is this important? Well, we know that
intake of dietary fiber has been associated
with decreased risk of cancer, inflammatory bowel disease,
diabetes, but we always don’t know
the mechanisms. One of the things we do know, that is in all of these
diseases, there is actually a decrease
in microbial diversity. So, I would postulate
that one of the mechanisms where dietary fiber
is working to decrease the risk of many
of these different diseases, is through its effects on
promoting microbial diversity. There’s also evidence to suggest
that dietary fiber can protect the mucous barrier.
In this study, gnotobiotic mice, that is mice
that actually lack microbes, were colonized with a cocktail
of human microbes. This was a cocktail
of 14 different microbes that represent the five
major phylum in humans. And, then they were
put on a fiber supplemented or a fiber deprived diet and infected
with an enteric pathogen. And, what they found was, that mice fed
the high fiber diet, had more fiber
degrading bacteria, a thick mucous lining, and are actually protected
from the colonization with citrobacter rodentium. In contrast, animals that were
fed the fiber deprived diet, actually promoted expansion
in activity of colonic mucosa degrading bacteria,
particularly akkermancia. And, they are more susceptible
to the rodentium infection and actually develop colitis.
Why this study is so important, is all the mice were colonized
with the exact same bacteria; and what this means, is that the availability
of potential food sources actually influences the growth
of different bacteria and can affect
the disease susceptibility. So, even if people have
the exact same microbes, what they eat can influence whether they might be
susceptible to various diseases. There’s also evidence
that suggests that there’s a relationship
between diet, microbial metabolism,
and cardiovascular disease. Dietary carnitine,
which is present in meat, and phosphatidylcholine
and choline, which are present
in cheese and eggs, can be metabolized by gut
bacteria to form trimethylamine. The trimethylamine
travels to the liver, where it’s metabolized
to trimethylamine oxide and in both human
and animal studies, this formation of TMAO
has been associated with increased risk of a number
of different diseases, including heart attack, stroke,
cancer, obesity, etcetera. You know, it’s so easy to look at single nutrients
in composition and we really need to be looking
at the totality of the diet. So, this study looked
at the relationship between dietary allicin
and carnitine and the production
of trimethylamine oxide. Mice were put on
either a chow diet, the diet supplemented
with carnitine, carnitine and allicin
or the chow diet and allicin. And, for those of you
that don’t know, allicin is one of
the bioactive sulfur compounds present in garlic. The animals were on the diet
for six weeks and then they were given
a carnitine challenge — and the results
are shown here. And, I’ll just take you
to the top slide. If you look at the red diet, the animals that were
fed carnitine, there’s a large increase
in the production of TMAO after the challenge. In contrast, if you look
at the yellow group, which is the group
that got carnitine and allicin, the allicin actually
inhibited the increase in TMAO production
after the carnitine exposure, suggesting that
we really need to look at the totality
of the diet. And, I’ll give you
another example on this. I think most people have heard
about the French paradox. The whole idea
that people in France drink a lot of red wine,
eat a lot of meat, but have a decreased risk
of cardiovascular disease. Well, there’s also evidence that
suggests from animal studies, that resveratrol
has a similar effect and actually inhibits
the production of TMAO. So, perhaps, this inhibition of
TMAO production by resveratrol is actually contributing
to the French paradox. Another important health effect
is obesity. As we all know, obesity has been
increasing over the years in the United States
and is also associated — has been suggested
to be mediated by changes in the microbiome. You know, it’s something
that’s happening more and more to all of us
and calorie intake is one of those things that more
is not necessarily better. But interestingly,
as we all know, some animals can eat more
and grow more than others, but there are actually
some animals that can eat more and grow less,
and this is germ-free animals. Those are the animals
that lack a microbiome. Early studies showed, that when
you compare germ-free animals to conventional animals, the germ-free animals had
42 percent less body fat, despite the fact
that they consumed 29 percent more chow
than conventional animals; however, mice practice
something called coprophagy. That means that they’ll actually
eat each other’s feces and if you take
these germ-free animals and put them in the cage
with the conventional animals, within two weeks, their body fat
and their chow consumption are similar to
the conventional animals, suggesting that these effects are being mediated
through the microbiome. There’s also evidence
from transplantation studies to suggest that the microbiome
in obese animals is different than those
in lean animals and it can be transferred. In these three
different studies, they took gnotobiotic animals — that’s animals that
don’t have a microbiome — and they gave them the
microbiome from obese animals, whether it be
genetic induced obesity, diet induced obesity,
or humanized mice — that’s mice getting feces
from lean or obese humans — and in all cases, they found
that those that got the obese had a significant increase
in body fat compared to those
that got the lean. And, there’s also evidence
to suggest that obesity can alter
the gut microbial composition. In these early studies,
when they compared both genetically induced obesity
and diet induced obesity, they found that the lean animals
had significantly less firmicute and significantly
more bacteroidetes compared to
the obese animals. These types of studies
have been replicated by a number of different
investigators, but only when a high fat diet
was utilized, not when a low-fat diet
was utilized. And, I’ll get to why that’s
important in a few slides. But, while we see these effects
in animals, the question is,
are they relevant to humans? In this study, they compared
12 unrelated obese subjects, and they found
that the obese subjects had significantly
more firmicutes and significantly
less bacteroidetes than five lean individuals. Moreover, if the subjects were
put either on a carbohydrate and/or a fat
restricted diet for a year, and allowed to lose up to
25 percent of their body weight, there was a significant
increase in bacteroidetes that correlate
with change in weight. So, this evidence suggests,
at least on an individual level, that an increase
in bacteroidetes appears to be beneficial
in terms of weight. However, when meta-analyses
were done comparing
several large studies, including the NIH
Human Microbiome Project, MetaHIT in Europe, and a lot
of other large studies, there was no correlation
between the bacteroidetes-to-firmicute
ratio and body weight. And, this is probably
because of the large interindividual variability
among individuals. As I said before, you know,
there are a lot of studies suggesting that there’s a
relationship between obesity and the microbiome; however, part of the problem
with a lot of these studies is that they compare animals
that are fed a high fat diet, compared to those that
are fed a chow diet, and perhaps they’re actually
utilizing the wrong comparison. So, this was a wonderful
study published in the last six months, which really tried
to disentangle the effects of diet
verses obesity. They had three different diets
in this study: a chow diet,
a refined low-fat diet, and a refined high fat diet. As you can see, the chow diet
and the refined low-fat diet had a similar
macronutrient content, where the refined high fat diet
was very high in fat; however, they had
very different fiber content. The chow diet had 15 percent
of the diet as fiber and the fiber came
from many different sources and was a non-purified diet. In contrast, the refined diet
had five percent in the diet as fiber,
and it was all cellulose. And, this is important, because cellulose
is a non-soluble fiber, so the bacteria
can’t actually utilize it. Here is the data. In terms of both body weight,
fat mass, and glucose tolerance, those mice fed
the refined high fat diet had significantly higher
fat mass, total body weight, and blood glucose
concentrations, yet there were no differences
in the refined low-fat diet compared to the chow diet.
When we looked at the firmicutes-to-bateroidetes
ratio, there were
no significant differences between the two
refined diets; however, these were both
different than the chow diet, both in the colon
and in the feces. So, what does this data mean?
It means that the high fat diet induced changes in mouse
gut microbiota composition and these effects
were due to diet, not to obesity, that glucose
intolerance and obesity in mice is linked to a high fat diet, not to changes
in the gut microbiota. And, one of the hypotheses
out there, when they started
showing these differences in microbial composition
in animals fed the high fat diet, was that they were better able
to extract energy from the diet, but this data actually shows
that the cecal fermentation — the energy harvest —
is decreased, not increased, by the high fat diet
as demonstrated by the decreased production
of short chain fatty acids. But, the important take home
message from all of this, is that the choice of diet
is vitally important to studies of
microbiota composition. As nutritionists, we always
believe that the best diet to utilize is an AIN-93
or and AIN-76 diet, because it’s a purified diet, we know exactly
what we’re feeding; however, they utilize cellulose which can’t be utilized
by the gut bacteria and it’s not going to be
as an energy source for them. So, there’s a need
to really better understand what diet you should be feeding
and to make sure that all groups are fed
an appropriate control diet, rather than just comparing
a chow with a purified diet. So, I hope I’ve convinced you that there’s a dynamic
relationship between the numbers
and types of microbes and dietary components
and energy consumption, that both of these can influence
the microbial metabolites and specifically
disease risk. But, the question is, is can
we utilize this information to predict what type
of dietary changes we should be doing to influence
disease susceptibility? There was a study
that was published a few years, that actually did this.
This was a study from Israel and they had a cohort
of about 800 individuals and they looked at
their glycemic response to different foods
and what they found was that, if you feed the different
individuals the same food, you’re going to have large
differences in their increase in blood sugar
as a response to that food. And, they wanted
to try and understand, can we predict
how different individuals will respond
to different foods? So, they utilized a combination
of gut microbiome analysis, blood tests, questionnaires,
anthropometrics, food diaries, continuous glucose monitoring
after giving specific foods — put this all into a computer and
developed a computer algorithm and said can we validate these
results in a validation cohort and can we do
a dietary intervention study? Comment by Gahche,
Jaime (NIH/OD) [E]: The speaker
did say dietaries, but she meant diaries. And, what they found, was that
there was high interpersonal variability
in the post-meal glucose observed
in the 800-person cohort, that utilizing the personal
and microbiome features enabled accurate
glucose response prediction, and in fact the prediction
was accurate and superior to common practice
in an independent cohort. And, most importantly, when they
took the 26 individuals, gave them a control diet
based on how they estimated or predicted
that they would respond, they actually found
that the personalized dietary interventions did successfully
lower post-meal glucose. While this is very
interesting results, the question
is always can be, can the study be reproduced
in a different population? Well, there’s a company —
it’s called DayTwo, you can go and Google them
and actually provide a sample and get an app if you want
to find out your microbiome and what you should
be eating — but investigators at
the Mayo Clinic bought the app and did an independent study
in 350 people trying to see, can they reproduce these results
in different people and were they able to predict
response and improve things? And, they found that they completely
reproduced the results. These studies are currently
being submitted for publication and there’s also
a push to do — well, the studies are currently
being conducted in a longer term follow up,
six to 12 months, as well in patients
with pre-diabetes and gestational diabetes. The other question is, is can
you extrapolate these results to other disease conditions? So, I need you to remember that,
when you go to eat lunch today, that you’re not
just feeding yourself, you’ll also be feeding
the microbes and what they may want to eat
might be different than what you want to eat. And, that you need to take
a metagenomic view of your dinner plate rather
than the traditional view. Think of all the different
dietary components that can be metabolized
by gut bacteria, what these metabolites are, and what their
biological effects might be. So, the take home message
is that microbiome research is an emerging area
of science, and there are many research
opportunities available. The microbiome is integral
to human physiology, maintenance of health,
and development of disease. That there is a two-sided
relationship between diet and microbiome and that nutritionist dietitians
in the food industry need to stay actively informed
about advances in this field, but this field still is
at the preliminary stages. And, most important,
bacteria are your friends. And, I’ll take questions now.
Thank you very much. [applause] So, any questions? Okay.>>Anita Pondroni: Hi,
Anita Pondroni from Hopkins. I had a question
about short chain fatty acids and the concentration levels. So, you talked about them
as mostly beneficial, but sometimes they can also
be seen as harmful, like propionic acid and butyric
acid for the nervous system, because they have
broad range implications on gene expression and oxidative
stress and inflammation and they’ve been
associated with, like, autistic disorder
and schizophrenia. So, could you comment on, maybe,
if it’s the difference in, like, concentrations
or is it, you know, maybe different methods
of action that they pose?>>Cindy Davis: I haven’t
really followed the propionic literature
as much, but a lot everything,
the dose influences a poison, all sorts of specific — I was really focusing more,
just on the butyrate and its effects
on beneficial effects in the gastrointestinal tract.>>Anita Pondroni: Sure,
thank you.>>Cindy Davis: You’re welcome.
Yes?>>Male Speaker: Okay,
in western countries, and I was born in India
and I am proud American, I made observation that we don’t
talk about constipation in this nation at all,
which is, in my opinion, could be playing
very important role in pathogenesis
of many diseases — including obesity
and of course many others.>>Cindy Davis: Absolutely,
and it’s probably influenced by the microbial composition and there’s actually
a large group at — well, there’s a large group in
a number of different societies, but are saying, are there
standardized measures that we should be including when we’re doing all different
types of human studies to better understand
changes in diet and how they’re effecting
microbial composition? And, part of it, does include
stool frequency and composition in things
to be thinking about.>>Female Speaker: With respect
to probiotics in dietary supplement form,
how do the microbes survive the acidic environment
of the stomach? Is it something to do with
the formulation of the capsules?>>Cindy Davis: Yes. So, the question was,
with probiotics, how do they survive the acidic
environment in the stomach? And, companies
put a lot of time into, looking at the best way
to package them to make sure they do.
In fact, one of the issues with a lot of probiotic
dietary supplements is that they have to have
the stated composition at the end of the half-life. So, most probiotic
dietary supplements, actually contain
significantly more live bacteria than are on the packages, just to make sure at the end
of the shelf-life that they actually have
that number of bacteria. Barbara?>>Female Speaker: So, I noted
that in your presentation, you very carefully distinguished
in the mouse data, certainly, between
microbes detected in the feces verses microbes
detected actually in the colon. So, what are the latest data
on the extent to which taking a probiotic, whether in food
or in capsule form, can actually change
the ecology and the organisms
living inside your gut as opposed to what’s
coming out the other end?>>Cindy Davis: So,
the question was, can probiotics in humans
influence microbial composition and the answer is,
in most individuals, no. There’ve been a number
of systematic reviews and meta-analyses
that have actually looked at, are there changes in microbial
composition with probiotics? And, in general, no. That’s not to say, that for
some individuals, there aren’t, and it probably depends
on your baseline microbiota. Whether — how long your taking
them and the amount your taking, what you’re eating
in combination, but that doesn’t mean, just because
they’re not colonizing that they may not be
having beneficial effects, because they still can be
exerting biological effects while they’re actually there.
Any other questions?>>Male Speaker: Yes.
First, one little comment. At Consumer, we test
the probiotics on the market. Years ago, we found
that many had only, you know, half or less than they claimed.
They’ve gotten much better. I think they realized
that they weren’t shipping and storing
these things properly.>>Cindy Davis: [affirmative]>>Male Speaker: So,
most recently, we’re not seeing
so much of a problem. My question is similar
to some of the others before. So, some of the most common
uses of probiotics now are for taking them
with antibiotics to prevent antibiotic
associated diarrhea. Do you think
that’s a real effect? I mean, there’s lots of studies,
mostly supported by industry, that show that.
What do you make of that and –>>Cindy Davis: I think that’s
one of the instances where they’ve shown
the most efficacy. The question is still, which
probiotic for which individual? But there definitely is,
when systematic reviews and — when systematic reviews
are done, they definitely, in general,
do show a protective effect. But, for a lot of the other
health effects, it’s not as strong. I do want to comment
on your first question about the analysis
of probiotics. I should mention
that the US Pharmocopeia has actually had a group
of investigators, right now, developing protocols
for analysis of probiotic dietary supplements
that can be invaluable — that are in development
to be able to actually analyze and show what they contain —
what they do contain.>>Male Speaker: Is that
breaking it down by strain?>>Cindy Davis: Yes.>>Male Speaker: And, is that
using any DNA technology or just plating
and things like that?>>Cindy Davis: It’s DNA
technology.>>Male Speaker: [affirmative]
Great, thanks.>>Cindy Davis: Question?
Back –>>Female Speaker: Hi.
Thank you for the talk. So, there are many different
techniques identifying, quantifying the microbial
composition in the community and my question is, well —
how comfortable are the results obtained from
different techniques, like say, 16 ounce RNA and DGG and/or chip
or shotgun sequencing? Will changing a method,
change the conclusion, by using the same sample?>>Cindy Davis: Well,
so the answer is that there are many
different methods. And, part of the problem is,
is — some of the methods we’ll just get
at which microbes are present? So, look, if you look at 16-S, it will tell you which microbes
are actually there. If you go to metagenomics,
such as shotgun sequencing, you can get a better idea
of biological function. So, they do answer
different questions and you will get
different results. Part of the problem right now, and I say this is
an evolving area of science, is they’re still trying
to determine, what are the best ways
to do these studies and one of the biggest
contributors to variability among studies, is actually,
how the DNA is isolated. So, I think
the important thing is, within a study, everything needs
to be processed the same way, samples need to be
compared to each other — whether that then
gives you the ability to compare between studies and would they get
the same results. It improves things,
but there still is variability when you go
from method to method.>>Female Speaker: Thank you.>>Cindy Davis: You’re welcome.
Here.>>Female Speaker: In
your opinion, is it more important for us
to have our patients really, be vigilant of what
they’re eating verses the intaking probiotics
or are they complementary?>>Cindy Davis: I think it’s
more important to be vigilant in what you’re eating. I think the studies
with dietary fiber show, that a high fiber intake
is extremely beneficial. I think having lots of fruits
and vegetables, whole grains — it’s the recommendations
that you would make for almost every specific
health condition in individuals and I still believe, in terms
of their effects on the microbe, it’s still the
best recommendations that you could be making too.
Thank you very much. [applause]