Your Gut Bacteria Affects Your Brain Function, Study Confirms
June 20, 2013
Story at-a-glance
The secret to improving your mood and brain health is in your
gut, as unhealthy gut flora can impact your mental health,
potentially leading to issues like anxiety, depression, autism
and more
A recent proof-of-concept study found that women who regularly
ate yogurt containing beneficial bacteria had altered brain
function compared to those who did not consume probiotics
Just as you have neurons in your brain, you also have neurons in
your gut -- including neurons that produce neurotransmitters
like serotonin, which is also found in your brain and is linked
to mood
Limiting sugar, eating traditionally fermented foods, and taking
a probiotic supplement are among the best ways to optimize your
gut flora and subsequently support your brain health and
normalize your mood
By Dr. Mercola
The bacteria, fungi, viruses and other microorganisms that
comprise your body’s microflora actually outnumber your body’s
cells 10 to 1, and it’s now becoming increasingly clear that
these tiny organisms play a MAJOR role in your health—both
physical and mental.
The impact of your microflora
on your brain function has again been confirmed by UCLA
researchers who, in a proof-of-concept study, found that
probiotics (beneficial bacteria) indeed altered the brain
function in the participants.
"Researchers have known that the brain sends signals
to your gut, which is why stress and other emotions can
contribute to gastrointestinal symptoms. This study shows
what has been suspected but until now had been proved only
in animal studies: that signals travel the opposite way as
well.
'Time and time again, we hear from patients that they
never felt depressed or anxious until they started
experiencing problems with their gut,' [Dr. Kirsten]Tillisch said. 'Our study shows that the gut–brain
connection is a two-way street.'"
The study, published in the peer-reviewed journal
Gastroenterology,2
claims the discovery “carries significant implications for
future research that could point the way toward dietary or drug
interventions to improve brain function.” Naturally, I urge you
to embrace dietary changes here, opposed to waiting for some
“miracle drug” to do the work for you...
Yes, Your Diet Affects Your Brain Function
The study enlisted 36 women between the ages of 18 and 55 who
were divided into three groups:
The treatment group ate yogurt containing several
probiotics thought to have a beneficial impact on intestinal
health, twice a day for one month
Another group ate a “sham” product that looked and
tasted like the yogurt but contained no probiotics
Control group ate no product at all
Before and after the four-week study, participants’ underwent
functional magnetic resonance imaging (fMRI) scans, both while
in a state of rest, and in response to an “emotion-recognition
task.” For the latter, the women were shown a series of pictures
of people with angry or frightened faces, which they had to
match to other faces showing the same emotions.
“This task, designed to measure the engagement of
affective and cognitive brain regions in response to a
visual stimulus, was chosen because previous research in
animals had linked changes in gut flora to changes in
affective behaviors,” UCLA explains.
Interestingly, compared to the controls, the women who
consumed probiotic yogurt had decreased activity in two brain
regions that control central processing of emotion and
sensation:
The insular cortex (insula), which plays a role in
functions typically linked to emotion (including perception,
motor control, self-awareness, cognitive functioning, and
interpersonal experience) and the regulation of your body's
homeostasis, and
The somatosensory cortex, which plays a role in your
body’s ability to interpret a wide variety of sensations
During the resting brain scan, the treatment group also
showed greater connectivity between a region known as the
“periaqueductal grey” and areas of the prefrontal cortex
associated with cognition. In contrast, the control group showed
greater connectivity of the periaqueductal grey to emotion- and
sensation-related regions. According to UCLA:
“'The researchers were surprised to find that the
brain effects could be seen in many areas, including those
involved in sensory processing and not merely those
associated with emotion,' Tillisch said...
'There are studies showing that what we eat can alter
the composition and products of the gut flora — in
particular, that people with high-vegetable, fiber-based
diets have a different composition of their microbiota, or
gut environment, than people who eat the more typical
Western diet that is high in fat and carbohydrates,' [senior
author Dr. Emeran] Mayer said. 'Now we know that this has an
effect not only on the metabolism but also affects brain
function.'"
What is really remarkable to me is that this study showed any
improvement at all, since they used commercial yogurt
preparations that are notoriously unhealthy foods loaded with
artificial sweeteners, colors, flavorings, and sugar. Most
importantly the vast majority have virtually clinically
insignificant levels of beneficial bacteria. Clearly, you would
be far better off making your own yogurt from
raw milk.
Your Gut May Hold the Key to Better Brain Health
You may not be aware that you actually have two nervous
systems:
Central nervous system, composed of your brain and
spinal cord
Enteric nervous system, which is the intrinsic nervous
system of your gastrointestinal tract
Both are created from identical tissue during fetal
development—one part turns into your central nervous system
while the other develops into your enteric nervous system. These
two systems are connected via the vagus nerve, the tenth cranial
nerve that runs from your brain stem down to your abdomen. It is
now well established that the vagus nerve is the primary route
your gut bacteria use to transmit information to your brain.
While many think of their brain as the organ in charge, your
gut actually sends far more information to your brain than your
brain sends to your gut... To put this into more concrete terms,
you've probably experienced the visceral sensation of
butterflies in your stomach when you're nervous, or had an upset
stomach when you were very angry or stressed. The flip side is
also true, in that problems in your gut can directly impact your
mental health, leading to issues like anxiety and depression.
For instance, in December 2011, the Journal of
Neurogastroenterology and Motility3
reported the novel finding that the probiotic (good bacteria)
known as Bifidobacterium longum NCC3001 has been shown to help
normalize anxiety-like behavior in mice with infectious colitis.
Separate research4
also found the probiotic Lactobacillus rhamnosus had a marked
effect on GABA (an inhibitory neurotransmitter that is
significantly involved in regulating many physiological and
psychological processes) levels in certain brain regions and
lowered the stress-induced hormone corticosterone, resulting in
reduced anxiety- and depression-related behavior.
Just as you have neurons in your brain, you also have neurons
in your gut -- including neurons that produce neurotransmitters
like serotonin, which is also found in your brain. In fact, the
greatest concentration of serotonin, which is involved in mood
control, depression and aggression, is found in your
intestines, not your brain. It’s quite possible that this
might be one reason why
antidepressants, which raise serotonin levels in your
brain, are often ineffective in treating depression,
whereas proper dietary changes often help...
Your Gut Microbes Can Affect Your Health in Numerous Ways
In recent years, it’s become increasingly clear that the
microbes in your gut play a much more vital role in your health
than previously thought possible. In fact, probiotics, along
with a host of other gut microorganisms, are so crucial to your
health that researchers have compared them to "a newly
recognized organ." Besides research implicating gut bacteria in
mental health and behavior, other research has shown that your
microbiota also has an impact on:
Immune system function: Biologist
Sarkis Mazmanian5
believes bacteria can train your immune system to
distinguish between "foreign" microbes and those originating
in your body. His work is laying the groundwork for new
therapies using probiotics to treat a variety of diseases,
particularly autoimmune diseases such as multiple sclerosis
and Alzheimer's.
Mazmanian and colleagues were recently awarded the
MacArthur Foundation "genius grant" for identifying an
organism that originates in the human body (opposed to a
fermented food) that has demonstrable health benefits in
both animal and human cells. The organism has been named
Bacteroides fragillis, and is found in 15-20 percent of
humans. His group hopes to one day be able to test this
body-originated bacteria in human clinical trials.
Gene expression: Researchers have
discovered that the absence or presence of gut
microorganisms during infancy permanently alters gene
expression. Through gene profiling, they were able to
discern that absence of gut bacteria altered genes and
signaling pathways involved in learning, memory, and motor
control. This suggests that gut bacteria are closely tied to
early brain development and subsequent behavior. These
behavioral changes could be reversed as long as the mice
were exposed to normal microorganisms early in life. But
once the germ-free mice had reached adulthood, colonizing
them with bacteria did not influence their behavior.
In a similar way,
probiotics have also been found to influence the
activity of hundreds of your genes, helping them to express
in a positive, disease-fighting manner.
Diabetes: Bacterial populations in the
gut of diabetics6
differ from non-diabetics, according to a study from
Denmark. In particular, diabetics had fewer Firmicutes and
more plentiful amounts of Bacteroidetes and Proteobacteria,
compared to non-diabetics. The study also found a positive
correlation for the ratios of Bacteroidetes to Firmicutes
and reduced glucose tolerance. The researchers concluded:
"The results of this study indicate that type 2
diabetes in humans is associated with compositional
changes in intestinal microbiota."
Obesity: The make-up of gut bacteria
tends to differ in lean vs. obese people. This is one of the
strongest areas of probiotic research to date, and you can
read about a handful of such studies
here. The bottom line is that restoring your gut flora
should be an important consideration if you're struggling to
lose weight.
Autism: Establishment of normal gut
flora in the first 20 days or so of life plays a crucial
role in appropriate maturation of your baby's immune system.
Hence, babies who develop abnormal gut flora are left with
compromised immune systems and are particularly at risk for
developing such disorders as ADHD, learning disabilities and
autism, particularly if they are vaccinated before
restoring balance to their gut flora.
Your gut bacteria are vulnerable to your diet and lifestyle.
If you eat a lot of sugar, refined grains, and genetically
engineered foods (i.e. processed foods and beverages of all
kinds, as they are typically loaded with high fructose corn
syrup and/or soy, both of which are primary GE crops in the US),
your gut bacteria are going to be compromised because processed
foods in general will destroy healthy microflora and feed bad
bacteria and yeast. Your gut bacteria are also very sensitive to
and can be harmed by:
Antibiotics, unless absolutely necessary (and when you
do, make sure to reseed your gut with fermented foods
and/or a probiotic supplement)
Conventionally-raised meats and other animal products,
as CAFO animals are routinely fed low-dose antibiotics,
plus
genetically engineered grains, which have also been
implicated in the destruction of gut flora
Processed foods (as the excessive sugars, along with
otherwise “dead” nutrients, feed pathogenic bacteria)
Chlorinated and/or fluoridated water
Antibacterial soap
Agricultural chemicals
How to Optimize Your Gut Flora
Considering the fact that an estimated 80 percent of your
immune system is located in your gut, reseeding your gut with
healthy bacteria is important for the prevention of virtually
ALL diseases, from colds to
cancer. To do so, I recommend the following strategies:
Avoid processed, refined foods in your diet.
Eat traditionally fermented, unpasteurized
foods: Fermented
foods are the best route to optimal digestive health, as
long as you eat the traditionally made, unpasteurized
versions. Some of the beneficial bacteria found in fermented
foods are also excellent
chelators of heavy metals and pesticides, which will
also have a beneficial health effect by reducing your toxic
load. Healthy choices include:
Lassi (an Indian yoghurt drink, traditionally
enjoyed before dinner)
Fermented milk, such as kefir
Natto (fermented soy)
Ideally, you want to eat a variety of fermented foods to
maximize the variety of bacteria you’re consuming. Fermented
vegetables, which are one of my new passions, are an
excellent way to supply beneficial bacteria back into our
gut. And, unlike some other fermented foods, they tend to be
palatable, if not downright delicious, to most people.
As an added bonus, they can also be a great source of
vitamin K2 if you ferment your own using the proper
starter culture. We tested samples of high-quality fermented
organic vegetables made with our specific starter culture,
and a typical serving (about two to three ounces) contained
not only 10 trillion beneficial bacteria, it also
had 500 mcg of vitamin K2, which we now know is a vital
co-nutrient to both vitamin D and calcium. Most high-quality
probiotic supplements will only supply you with a fraction
of the beneficial bacteria found in such homemade fermented
veggies, so it’s your most economical route to optimal gut
health as well.
Take a high-quality probiotic supplement.
Although I'm not a major proponent of taking many
supplements (as I believe the majority of your nutrients
need to come from food), probiotics is an exception if you
don’t eat fermented foods on a regular basis.
Nurturing Your Gut Flora Is One of the Foundations of Optimal
Health
Mounting research indicates the bacterial colonies residing
in your gut may play key roles in the development of cancer,
asthma, allergies, obesity, diabetes, autoimmune diseases and
even brain, behavioral and emotional problems like ADHD, autism
and depression. When you consider the fact that the gut-brain
connection is recognized as a basic tenet of physiology and
medicine, and that there's no shortage of evidence of
gastrointestinal involvement in a variety of neurological
diseases, it's easy to see how the balance of gut bacteria can
play a significant role in your psychology and behavior as well.
With this in mind, it should also be crystal clear that
nourishing your gut flora is extremely important, from cradle to
grave, because in a very real sense you have two brains,
one inside your skull and one in your gut, and each needs its
own vital nourishment. Eating fermented foods should be your
primary strategy, but if you don't enjoy the taste of fermented
foods, taking a probiotic supplement is definitely advised. I
recommend looking for a probiotic supplement that fulfills the
following criteria, to ensure quality and efficacy:
The bacteria strains in the product must be able to
survive your stomach acid and bile, so that they reach your
intestines alive in adequate numbers
The bacteria strains must have health-promoting features
The probiotic activity must be guaranteed throughout the
entire production process, storage period and shelf life of
the product