Last updated November 1, 2021.
Edited and medically reviewed by Patrick Alban, DC. Written by Deane Alban.
Psychobiotics are intestinal bacteria with proven mental health benefits. Help reduce anxiety and depression with the right probiotics and prebiotic foods.
There’s a 3-pound part of you that affects your thoughts and feelings, and runs your life more than you would expect.
Surprisingly, it’s not your brain; it’s the total biomass of bacteria that lives in your intestines.
There’s new evidence that bacteria in the gut are integrally linked to the workings and the health of your brain.
Researchers are just beginning to understand how a class of probiotics called psychobiotics could be used to modify gut bacteria to alleviate anxiety, depression, and more.
This exciting new discovery is being called “the new frontier” in mental health treatments.
What Are Psychobiotics?
The term psychobiotics was first coined in 2013 by Ted Dinan, MD, PhD, a renowned authority on the microbiome.
This term sounds high-tech but, in fact, is a twist on the more familiar probiotics — live microorganisms that are beneficial to health.
Psychobiotics are probiotics that specifically bestow mental health benefits.
More recently, the definition for psychobiotics has been expanded to include prebiotics — substances that act as food for beneficial microorganisms, encouraging their growth.
How Psychobiotics Work: The Gut-Brain Connection
To fully understand how psychobiotics work, a little background on the connection between the gut and the brain is in order.
The intestines have their own nervous system which has been called the “second brain” or “backup brain.”
Neurons are generally associated with the brain, but amazingly, your intestines contain 100 million of them — more than either your spinal cord or peripheral nervous system!
" More than 90% of your total serotonin and 50% of your dopamine is found in your intestines.
The English language is filled with terms that reflect the gut-brain connection — gut-wrenching, gut instinct, gut feeling, and butterflies in the stomach.
But it’s not just the intestines that have a two-way communication channel with the brain.
Strangely, the bacteria that reside there do as well.
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Your intestines house an estimated 100 trillion microbes comprised of over 1,000 different species and 7,000 distinct strains of bacteria.
Each of us has a microbiome as unique as our fingerprints.
Virtually everything you do and everything that happens to you from the moment you’re born contributes to the creation of your unique gut flora profile.
Factors that impact your gut flora include your age, gender, lifestyle, geographic location, diet, stress, and antibiotic use.
And, in turn, your microbiome impacts how you behave, think, and react to stress, and how predisposed you are to a number of brain disorders.
It’s estimated that a healthy gut should contain a ratio of about 85% “good” or “friendly” bacteria to 15% “bad” bacteria.
When this ratio is out of balance, it results in a condition called dysbiosis.
A dysfunctional microbiome can be the root cause of anxiety, depression, ADHD, memory loss, concentration issues, chronic inflammation, obesity, and more.
Gut microbes may even play a role in personality.
Researchers have developed germ-free mice that are born with no gut bacteria and live in sterile environments.
When a germ-free mouse is exposed to the bacteria of a normal mouse, it adopts aspects of the donor mouse’s personality!
6 Ways Psychobiotics Impact Brain Health and Function
Probiotics work in a wide variety of ways to improve overall health.
They crowd out “bad” bacteria, aid digestion, break down toxins, and synthesize certain essential nutrients such as folic acid, niacin, vitamin B12, and vitamin K.
But to qualify as a psychobiotic, a probiotic must specifically provide mental health benefits.
There are many existing theories on how psychobiotics affect the brain.
Here’s a look at the most likely mechanisms.
1. Psychobiotics Communicate Via the Vagus Nerve
The vagus nerve is the longest cranial nerve, relaying messages between the intestines and the brain while touching many organs in between.
It is thought to be a major way that psychobiotics exert influence on the brain.
Dr. Ted Dinan’s research supports this.
He and his colleagues found that when mice were given the probiotic Lactobacillus rhamnosus, they showed fewer signs of stress, anxiety, and depression.
But mice with a severed vagus nerve did not experience the same benefits.
2. Psychobiotics Synthesize Neurotransmitters
Neurotransmitters are chemicals that brain cells use to communicate with each other.
But neurotransmitters aren’t found only in the brain.
The gut’s enteric nervous system (ENS) makes over 30 neurotransmitters.
This enables the ENS to work on its own to control digestion, with no input from the brain.
The major neurotransmitters serotonin, GABA, dopamine, acetylcholine, and norepinephrine have all been reported to be synthesized by gut microbes.
More than 90% of your total serotonin and 50% of your dopamine is found in your intestines.
Here’s a chart that shows some common gut bacteria and the neurotransmitters they create.
3. Psychobiotics Reduce Stress Hormones
Another way psychobiotics work is by reducing stress hormones.
Some strains of psychobiotics have been shown to significantly reduce levels of the stress hormone cortisol.
Chronically elevated cortisol is linked to brain fog, anxiety, depression, mood swings, memory loss, concentration problems, weight gain, sleep problems, digestive issues, and even mental disorders like schizophrenia.
Study participants who took a combination of Lactobacillus helveticus and Bifidobacterium longum for one month experienced a large drop in cortisol levels and significant improvement in mood.
4. Psychobiotics Suppress Brain Inflammation
Inflammation is a natural healing mechanism.
But it can get stuck “on,” leading to inflammatory diseases such as allergies, arthritis, psoriasis, colitis, dermatitis, sinusitis, and any other health condition that ends in “itis.”
When chronic inflammation sets up in the brain, it can cause a host of brain-related disorders, including depression.
Good bacteria protect the brain from inflammation by keeping the levels of pro-inflammatory chemical messengers called cytokines in check.
High cytokine levels have been linked to mood disorders, depression, anxiety, memory loss, and cognitive disorders.
But certain species and strains of psychobiotic bacteria have been found to reduce inflammation, resulting in fewer anxiety and depression symptoms.
5. Psychobiotics May Promote New Brain Cell Formation
Psychobiotics may work by increasing levels of brain-derived neurotrophic factor (BDNF).
This important brain protein has natural antidepressant properties and acts like fertilizer to stimulate the formation of new brain cells.
So far, this effect from psychobiotics has been observed only in lab animals, not in humans.
6. Psychobiotics Protect the Brain From Damage
Lactobacilli and Bifidobacteria are two of the most prevalent groups of bacteria in the gut.
They are the mainstays in most probiotic supplements and occur in abundance in probiotic foods.
Some strains of Lactobacilli and Bifidobacteria act as antioxidants, protecting brain cells from free radical damage.
Additionally, good bacteria prevent the overgrowth of bad bacteria which create toxic byproducts called lipopolysaccharides.
Lipopolysaccharides have numerous negative effects on the brain including:
- Lowering levels of the mood-enhancing neurotransmitters dopamine and serotonin
- Causing damage to the hippocampus, the area of the brain considered the seat of memory
- Contributing to short-term memory loss
- Increasing levels of the stress hormone cortisol
- Increasing inflammation, an underlying cause of depression
- Increasing free radical damage to brain cells
Evidence-Based Mental Health Benefits of Psychobiotics
The research on the potential benefits of psychobiotics is very promising.
There’s evidence that they can bring relief to some of the most common mental conditions of our times, including anxiety, depression, and memory loss, as well as the effects of stress.
Here’s a sampling of research highlights on the benefits of psychobiotics:
A review of 38 studies found that probiotics effectively reduced symptoms of anxiety, depression, autism, and obsessive-compulsive disorder, while improving various kinds of memory.
A meta analysis of 96 trials found that probiotics were associated with a significant reduction in depression.
One bacteria, Bifidobacterium infantis, was found to alter levels of serotonin much like the antidepressant Prozac.
A mix of Bifidobacterium and Lactobacillus species was found to reduce sadness, rumination, and aggressive thoughts.
A clinical trial using a particular strain of bacteria, Bifidobacterium longum 1714, modulated the stress response and enhanced cognition in healthy adults.
How to Optimize Your Mental Health With Psychobiotics
The evidence is clear that psychobiotics can lead to numerous mental health benefits.
But determining which strains of probiotics are the best for the many brain disorders that exist is definitely a work in progress.
The general consensus among experts is that researchers have just scratched the surface and a lot more research is needed.
Most studies use species of Bifidobacterium (B. longum, B. breve, or B. infantis) or Lactobacillus (L. helveticus or L. rhamnosus) bacteria.
This means there are still 1,000 additional species of bacteria to be considered!
Experts in the field believe that clinically tested psychobiotics won’t be available for several years.
So, while it’s unlikely that your doctor will be prescribing psychobiotics anytime soon, there is still much you can do on your own to optimize your microbiome right now.
1. Take a Psychobiotic Supplement
You can take probiotic supplements that qualify as psychobiotic, but finding one that contains proven species can be a challenge.
Psychobiotics expert Dr. Ted Dinan warns consumers not to fall for false claims.
Discouragingly, he insists that few probiotics marketed as cognitive enhancers or mood boosters offer any real benefits.
He contends that most probiotic supplements are on the market because they are easy to manufacture, not because they are effective.
He states that “most don’t make it past the stomach acid.”
There are very few probiotic supplements developed specifically for mental health and not all strains used in studies are commercially available.
How to Read a Psychobiotic Supplement Label
The label below is from a supplement with some science behind it, Mood Probiotic by InnovixLabs.
It contains two species of probiotics, Lactobacillus helveticus and Bifidobacterium longum, which have been proven beneficial to mood.
Also, notice the designations “Rosell-52ND” and “Rosell-175.”
These identify specific strains that are usually trademarked by the manufacturers.
When buying any probiotic or psychobiotic, look at the colony forming unit (CFU) number.
This is the estimated number of live microbes in each serving.
A typical probiotic dosage for adults is 10 to 20 billion colony-forming units per day.
2. Take a Probiotic Supplement for General Health
If you aren’t sure where to start, consider a probiotic that contains a variety of Lactobacillus and Bifidobacterium species.
These are the two best groups of probiotics that support both brain health and general health.
3. Eat Probiotic Foods
There are several drawbacks to taking probiotic supplements.
There is no guarantee that they contain what is stated on the label.
When researchers randomly tested commercially available probiotic products, they found that only one out of 17 probiotic supplements was accurately labeled.
There’s doubt whether these microbes make it alive past your highly acidic stomach.
And you don’t know if you’re getting the right ones for your needs.
Dr. Dinan emphatically states in his book The Psychobiotic Revolution: Mood, Food, and the New Science of the Gut-Brain Connection that “Eating the right kinds of foods has always been and still is the best way to achieve and maintain a healthy gut.”
Eating probiotic foods — foods that contain beneficial microbes — is the most sustainable way to increase your good gut bacteria.
Virtually all healthy traditional diets wisely included fermented foods which contain Lactobacillus and Bifidobacterium, mainstays of probiotic and psychobiotic supplements.
Add these fermented foods to your diet to boost your friendly flora naturally.
Fermented Dairy Products
Yogurt is the most commonly consumed fermented dairy product.
But not all yogurt contains live cultures and most are low-fat versions that are loaded with sugar or artificial sweeteners.
Choose unsweetened, full-fat products that state that they contain live cultures.
Sugar and artificial sweeteners negate yogurt’s probiotic effects and low-fat versions contain fewer good bacteria.
Fermented Soy Foods
Fermented soy foods include miso, tempeh, and tamari.
Stick with traditionally fermented products.
Most soy sauce is chemically produced rather than fermented.
Some popular fermented vegetables include pickles, sauerkraut, and kimchi.
Look for those that are traditionally fermented and labeled unpasteurized.
Avoid vegetables that are simply soaked in vinegar.
4. Eat Prebiotic Foods
Prebiotics are foods that contain insoluble fibers that the “good” intestinal bacteria feed on.
Ingesting probiotics without them is like trying to grow flowers by spreading seeds on concrete.
Some experts believe that prebiotics are even more important than probiotics for maintaining healthy microflora.
Prebiotics alone can reduce stress, anxiety, and depression.
Unwisely, most of us grab unhealthy foods like pizza, chips, and ice cream as our comfort foods.
A smarter idea would be to grab foods high in probiotics or prebiotic fibers instead, such as a yogurt “sundae” topped with a banana and dark chocolate chips.
While virtually all plant foods contain fiber, these foods are particularly high in prebiotic fibers:
- bamboo shoots
- black pepper
- dark chocolate
- fennel root
- Jerusalem artichokes
- legumes (especially lima beans and lentils)
- mustard greens
- yacón (a natural sweetener)
To learn more about incorporating both probiotics and prebiotic foods into your diet, read neurologist Dr. David Perlmutter’s cutting-edge book Brain Maker: The Power of Gut Microbes to Heal and Protect Your Brain for Life.
5. Play in the Dirt
Not all beneficial bacteria enter by way of your mouth.
Simply inhaling Mycobacterium vaccae, a bacteria found in soil, can improve your mood by stimulating the production of serotonin.
M. vaccae activates the same neurons in the brain as the antidepressant Prozac.
This may be one of the reasons gardeners feel relaxed and happy when engaging in their favorite pastime.
6. Stop Killing Your Good Bacteria
Antibiotics are the biggest danger to your microbiome since they indiscriminately kill good bacteria along with the bad.
But so do many other prescription medications, with proton-pump inhibitors, metformin, antibiotics, and laxatives at the top of the list.
But less obvious factors such as stress, sugar, artificial sweeteners, alcohol, food emulsifiers, chlorinated tap water, exposure to environmental toxins, and the widespread use of antibacterial soap and hand sanitizers also contribute to the demise of good bacteria.
Why We Must Rethink Our War on Bacteria
The use of antibiotics against infectious diseases is arguably the most important medical advance of all time.
But there’s a lot of evidence that we’ve gone too far.
Antibiotic overuse has made antibiotic-resistant bugs a frightening reality.
An alarming 70% of all antibiotics are used in livestock feed.
Veterinary antibiotics have been detected on produce like carrots and lettuce as well as in our drinking water.
And our collective mental health may be suffering from it.
It’s time to stop our war on microbes and accept our evolutionary symbiotic relationship with them.
Bacteria have been found living in the most hostile environments on earth.
Live microbes were found trapped inside 50,000-year-old cave crystals in Mexico.
They’ve even been found growing on the outside of the International Space Station!
Bacteria are that ubiquitous and that tough.
And without them, life as we know it could not exist.
Watch the Video
In this engaging TEDx Talk on YouTube, nutritionist, microbiologist, and neuroscientist Ruairi Robertson explains that our gut bacteria are as naturally diverse as an Amazon rainforest.
Unfortunately, our war on bacteria has left our collective intestines a barren wasteland instead.
Psychobiotics: Take the Next Step
Psychobiotics are live microorganisms that impart mental health benefits.
They can positively impact your brain health and function in a variety of ways.
They show promise for becoming the next generation of treatment for anxiety, depression, and other mental disorders.
But don’t expect your doctor to prescribe one in place of psychiatric medication any time soon.
More research is needed and it may be years before we get to that point.
But, in the meantime, you can optimize your intestinal microflora by eating a diet that contains both probiotics and prebiotic foods, taking appropriate probiotic supplements, and by limiting your use of antibiotics and other known factors that destroy good bacteria.
Encouraging the growth of good gut microbes is a very important step that you can take to optimize your mental health.
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