Imbalanced gut bacteria may increase your risk of anxiety, depression, obesity and a host of other diseases. Learn how digestive bacteria can cause anxiety and find out how dietary changes can help you instill or protect an optimal balance of beneficial bacteria.
Butterflies in your stomach before a public
speech; a stressful meeting that causes stomach pain - you already know
that emotional states have gastrointestinal consequences, but did you know that
gut bacteria imbalances can also damage mental health?
100 trillion bacteria call your gut home; you're carrying roughly 5 pounds of bacteria, viruses and other eukaryotes right now!1 These microbes play essential roles in our body. Keep a good balance of beneficial gut bacteria and you protect health and well-being. Let bacteria slide out of balance and you put your physical and mental health at risk.
Read on to learn more about
The roles bacteria play in your gut
Research that supports gut bacteria’s influence on anxiety,
depression and weight management
Diseases and conditions associated with gut bacteria
imbalances
How to promote healthy gut bacteria levels
What Gut Bacteria Do
Your gut (your digestive tract) is essentially a long tube
that begins at the back your mouth and continues to your stomach, small
intestines, and to the colon and anus.
Your gut is the only organ that has its own nervous system
(with over 100 million neurons residing within the walls of the organ).
You start out as a newborn with a sterile gut. By age 2 to 4 you have 100 trillion bacteria in your gut. Everyone has a unique mix of different bacterial populations. This mix is
influenced by where you live, what you eat, your genetics, your experiences as an infant and other environmental factors
Gut bacteria play an essential role in the manufacture of
neurotransmitters - such as 95% of the brain’s serotonin. (Serotonin is an
important messenger in the brain and in the GI tract. Significantly, children
who lack certain types of gut bacteria in early development will never produce
as much serotonin, even in adulthood, as children with more diverse
microflora.)2
Gut bacteria help with the digestion and
metabolism of food. They extract vitamins and maintain the gut wall - and once beneficial bacteria colonize
the gut, they repel pathogens that would otherwise
establish a foothold. They do this by optimizing pH and out-competing
‘invaders’ for nutrients.
Gut bacteria communicate with dendritic cells of the immune
system to quicken the response to harmful germs3 4
We are composed of 30 000 human genes and
carry roughly 3 million bacterial genes. Given this, is it any wonder that bacteria have such an
influence on so many systems of the body, including cognition and emotional
regulation?5
Research: Gut Bacteria’s Influence on Anxiety
Transforming Behavior with Bacteria
Using mice, scientists at McMaster University in Ontario
demonstrated that altering gut bacterial levels with antibiotics changes behaviors and anxiety levels.
After antibiotics and gut bacterial disruption, mice that
were normally cautious became adventurous and less anxiety-prone. Or,
in another experiment, the researchers demonstrated that by injecting normally
active mice with bacteria from more passive mice, they transformed the active mice
into timid creatures.
The researchers conclude that altering gut microflora with antibiotics or diet may cause
emotional or behavioral changes; they suggest research on the use
of probiotics as treatments for behavioral disorders.6
UCLA Yogurt Study
UCLA researchers say eating probiotic
yogurt twice daily for a month changes the
brain’s response to threatening stimuli and induces structural changes in the cortex – dampening reactivity within areas of
the brain that cause emotional spikes in response to bodily sensations.
Compared to subjects who ate no probiotic yogurt, subjects
given a month of twice daily probiotic yogurt:
Showed less neural-emotional response to pictures of threatening faces – particularly in areas of the brain that process and
integrate bodily sensations into emotional and cognitive reactions.
Had increased connections within cognition areas of the
prefrontal cortex
So if a twinge in your gut spikes your anxiety, you may want
to consider adding a couple of probiotic yogurts a day.7
Chronic Fatigue Anxiety Study
Subjects with chronic fatigue syndrome were given either
probiotics supplements or a placebo for 2 months. After 2 months, those given
the probiotics had significantly reduced anxiety scores as measured by the Beck
Anxiety Inventory.8
Research: Gut Bacteria’s Influence on Depression
Early-Life Bacterial Deficits Create Life-Long Serotonin Deficits
Gut bacteria play an essential role in the production of
serotonin and low serotonin levels are associated with an increased depression
risk. In an animal model experiment, Irish researchers found that mice lacking certain gut bacteria during infancy never developed normal serotonin levels, even when they were colonized with essential
bacteria later in life. A bacterial deficit in early-life caused an
irreversible serotonin deficit through adulthood.9
Research: Gut Bacteria’s Role in Weight Management
Not convinced that gut bacteria play an important role in
obesity? Then consider this - give a sample of your gut bacteria to scientists
at The University of Florida’s Center for Biotechnical Research and they’ll
predict your obesity or leanness with 90% accuracy.10
Danish Obesity Study
In a study of obese and non-obese people in Denmark, obese
people were found to have less gut bacterial diversity than healthy-weight people -
and over the 9 year study period, people with the least bacterial diversity
gained the most weight.11
Bacteria Change Leads to Weight Gain
In an animal model study, mice colonized with bacteria from
an obese mouse gained weight more quickly than mice colonized with bacteria from
a lean mouse.12
How Does Gut Bacteria Change Brain Function?
Researchers don't yet know exactly how gut bacteria influence our moods, but
they’re pretty sure that the vagus nerve - a nerve-line which sends information from the
gut to the brain - serves as one key pathway of
influence.
Vagus Nerve Experiment
Mice fed a lactobacillus spiked diet became more adventurous and suffered less from stress. They also became more responsive to the
neurochemical GABA (a chemical which is also targeted by medications like
Xanax.)
However, when the scientists severed the vagus nerve, feeding lactobacillus to mice no longer caused any changes to
stress, anxiety or GABA systems.13
Gut bacteria may also cause the release of chemical
messengers from the gut into the bloodstream, and eventually into the brain.
What Is Gut Dysbiosis?
Dysbiosis - The condition of having an imbalanced microbiome; too much harmful bacteria and not
enough beneficial bacteria.14
An imbalance in the gut impairs
beneficial bacteria. Since beneficial bacteria play essential roles in
digestion, immune system functioning and even mental health, this can lead to serious health conditions, like
Obesity and other metabolic disorders
Immune disorders
Type 2 diabetes
Endotoxemia
Inflammatory bowel disease (IBS)
Aggravated existing liver disease
Food allergies
Diminished mental health
How to Protect Healthy Gut Bacteria
100 trillion gut bacteria live and work in an average digestive
system. They play important roles and when they get imbalanced we get
diseases and mental health problems.
Given this, it makes sense to try to protect out microbiome - to encourage a good balance of beneficial bacteria. Here are a few general tips on maintaining good bacterial health:
Avoid unnecessary antibiotic use and limit antibiotic use to
short courses, whenever possible
Encourage beneficial bacteria with a diet high in probiotics
and prebiotics
Avoid intestinal parasites and if exposed get treated
promptly
Be cautious with GERD drugs like proton pump inhibitors
which drastically reduce stomach pH. This alteration in pH can lead to
a dramatic change in gut flora and in some cases, growth of harmful bacteria at
the expense of beneficial bacteria more accustomed to normal stomach pH levels.15
Avoid excessive stress – animal research shows that long
periods of stress lead to substantial declines in certain beneficial bacteria.16
Breastfeed infant children
Watch out for excessive hygiene and let small children get a
little dirty every now and again – studies show that animals reared in sterile environments don’t develop the same healthy gut microflora
as animals raised more naturally.17
Make healthy eating choices – minimize consumption of high
sugar, high fat and processed foods and maximize consumption of fiber-rich
vegetables and fruits (see below for more on how diet influences your
microbiome).
Dietary Choices for a Healthy Microbiome
People who consume high fiber, plant-based diets tend to
have healthier microflora than people who consume a diet that’s higher in fats
and simple carbohydrates (a junk-food diet!)
To encourage a healthy bacterial balance:
Avoid a high fat diet – a high fat diet leads to the
decrease or elimination of Bifidobacteria spp, a bacterium which plays an
essential role in the protection of the gut barrier.
Avoid a high sugar diet – too much refined sugar leads to
excess bile production and creates a welcoming environment for the opportunistic pathogens C. difficile and C. perfringens (C. difficile is a
super-bug that can cause symptoms ranging from mild diarrhea to
life-threatening colitis.)18
Eat more complex carbohydrates – Complex carbs encourage the
growth of beneficial colonies of paratuberculosis and enterobacteriaceae and
increase levels of Bifidobacteria spp
Consider a high fiber vegetarian diet – high fiber
consumption leads to significant fatty acid production (as microbes break-down
these fibers.) This lowers pH and decreases pathogenic e-coli bacteria
levels.19
Dietary Sources of Probiotics and Prebiotics
If you have gut dysbiosis, restoring a healthy gut
microbiome should get you feeling a lot better.
One way to restore gut health is through the consumption of
probiotic and prebiotic foods.
These foods are generally very healthy for all people, so
with pre and probiotics you have very little to lose and potentially much to
gain
Probiotic foods are foods high in beneficial bacteria. Some
examples of probiotic foods are:
Yogurt (buy one that indicates live active culture on the
label)
Kefir – a fermented dairy drink
Sauerkraut
Natto
Miso
Kimchi
Fermented pickles
Prebiotic foods are foods high in the soluble fibers that feed
beneficial bacteria – the idea is you can sustain a healthy microbiome by
feeding it well. Some examples of prebiotic foods are:
Bananas
Honey
Garlic
Onions
Leeks
Whole grains
Artichokes
Asparagus
Chicory
Are Probiotic Supplements Safe?
As an alternative to pro and prebiotics consumed through
food, you can also take a daily dose through supplements.
According to The National Center for Complementary and
Alternative Medicine (NCCAM) probiotics are generally well-tolerated and cause few
side effects. There is little research evidence to support their long-term
safety (or harm). People with pre-occurring serious health conditions may be at
greater risk of serious side effects.20
Image Copyright: NIAID