Psychobiotics: Use the Gut-Brain Connection for Mental Health

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Last updated March 29, 2023.
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 microbes — bacteria, fungi, and viruses — that live in your intestines.

There’s new evidence that bacteria in the gut are integrally linked to the function and health of the 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 our total serotonin and 50% of our dopamine is found in our 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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Our 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, sex, 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, attention disorders, 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.

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1. Psychobiotics Communicate Via the Vagus Nerve

The vagus nerve is the body’s longest 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, norepinephrine, and oxytocin have all been reported to be synthesized or increased by gut microbes

More than 90% of our total serotonin and 50% of our dopamine is found in our intestines. 

Here’s a chart that shows some common gut bacteria and the neurotransmitters they create.

bacteria neurotransmitter synthesis chart
Common gut bacteria and the neurotransmitters they create. (Image courtesy of

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


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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

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How to Reduce Cortisol, the Stress Hormone

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 many other health conditions that end 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

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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

This effect from psychobiotics has been observed in animals and, more recently, 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 bacterium, 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.

psychobiotic supplement label
A typical psychobiotic supplement label.

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 our highly acidic stomach.

Even if they do survive, we don’t know if they actually colonize.

And, finally, you don’t know if you’re taking the ideal 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 include fermented foods that contain Lactobacillus and Bifidobacteriummainstays of probiotic and psychobiotic supplements

Add these fermented foods to your diet to boost your friendly flora naturally.

But avoid heating these foods, or you’ll destroy their benefits. 

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.

For instance, most soy sauce is chemically produced rather than fermented.

Fermented Vegetables

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:

  • artichokes
  • asparagus
  • bamboo shoots
  • bananas
  • barley
  • beets
  • black pepper
  • broccoli
  • chicory
  • coffee
  • dark chocolate
  • endive
  • fennel root
  • garlic
  • ginger
  • honey
  • Jerusalem artichokes
  • jicama
  • leeks
  • legumes (especially lima beans and lentils)
  • mustard greens
  • onions
  • rye
  • tomatoes
  • wheat
  • 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 our microbiomes 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.

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