The Brain-Gut Connection: How Unbalanced Gut Bacteria Affect Your Mental Health

by Dr. Matt Olesiak, M.D.

Is There a Brain-Gut Connection in Mental Health?

There is growing evidence that our brains and digestive systems are more interconnected than we previously thought - potentially impacting our mental health.

This article discusses how the gut affects the brain and mental health and what it means for you.

A graphical image of human intestines with bacteria in the large intestine.

What's Involved in the Gut-Brain Connection?

The gut-brain connection or the gut-brain axis refers to the bidirectional network of communication between your gut and your brain (1, 2). Your central nervous system, vagus nerve, neurotransmitters, and gut microbes are involved in this communication network.

Vagus Nerve and Nervous System

What is the vague nerve?

The vagus nerve is the longest and most complex cranial nerve in the human body. It is the principal component of the parasympathetic nervous system, which regulates a large variety of vital biological activities, such as mood, immunological response, digestion, and heart rhythm.

Your brain and gut are physically connected by the vagus nerve, which travels from your brain to your large intestine.

Researchers have found that the vagus nerve is critical in transmitting signals between the gut and brain in animals and humans (2, 3) and that this connection can affect mood and mental state.

For example, it is known that stress can cause digestive system upsets and even stomach ulcers. So how can mental or emotional stress affect the digestive system? The answer lies in the vagus nerve.

A graphical illustration of the vague nerve and its pathway through the human body and its organs, including the brain, lungs, liver, spleen, kidney, and intestines, with explanatory text described below.

Explanatory Text

Vagus nerve. Brain. Pons, Medula Oblongata,, vagus nerve, superior ganglion of the vagus nerve, inferior ganglion of the vagus nerve, pharyngeal branch, laryngeal branches, lungs, cardiac branch, pulmonary plexus, liver, stomach, esophageal plexus, spleen, celiac plexus, kidney, colon, small intestine.

End Explanatory Text

Studies conducted on animals have demonstrated that stress impairs signals sent through the vagus nerve, causing gastrointestinal disorders (4).

Additionally, a human study found that those with irritable bowel syndrome (IBS) or Crohn's disease demonstrated a diminished vagal tone compared to those without these conditions. This suggests an association between impaired vagal function and IBS. (5).

Several studies indicate the vagus nerve's effect on mental health and other conditions. For example, an intriguing study on mice revealed that feeding them a probiotic (beneficial live bacteria) lowered their blood levels of stress hormones. However, the probiotic had no impact when the vagus nerve was severed (6).

Here's another interesting fact about mental health and the gut microbiome.

An estimated 100 billion neurons in the human brain and nervous system send signals throughout your body. Without them, your body would be unable to function (7).

It is interesting to note that your gut also contains neurons -- about 500 million neurons, to be exact -- that interact with those in your brain and nervous system via the vagus nerve (8).

Neurotransmitters

A silhouette of a human head and neck with multi-colored electrical lights sparking from the head.

There is also a connection between your gut, brain, and mental state via chemicals called neurotransmitters.

The brain produces neurotransmitters that regulate emotions and feelings. But, surprisingly, the gut and its trillions of bacteria and other microbes also make a significant portion of neurotransmitters, particularly serotonin and gamma-aminobutyric acid (GABA).

Serotonin is a hormone and neurotransmitter that plays a crucial role in regulating several physiological processes, including sleep, body temperature, hunger -- and mood. Indeed, serotonin is often called the "happy chemical."

Research suggests insufficient serotonin levels may contribute to depression, anxiety, and other mood disorders.

GABA, an inhibitory neurotransmitter, is the other mood chemical created in your brain and gut. Studies show that GABA helps suppress feelings of anxiety, fear, and stress.

Gut Microbes

Gut microbes also play a significant role in brain function.

For example, short-chain fatty acids (SCFA) like butyrate, propionate, and acetate are the primary metabolites produced by bacterial fermentation of fiber in the colon. They affect brain function in many ways (9).

Several beneficial bacteria produce these short-chain fatty acids, which may influence brain health in various ways.

For example, research suggests that SCFAs may cross the blood-brain barrier through specific endothelial cells, supporting brain function. They also help build and support the blood-brain barrier, which keeps toxins away from the brain.

Additionally, butyrate is the primary fuel source for your gut lining, so it contributes to the strength and integrity of the gut barrier.

SCFAs may also act as neurotransmitter modulators.

Another way gut microbes affect mental health is through the immune system and its inflammatory response.

You see, your gut barrier and gut microbes are essential in what enters the bloodstream and is excreted from the body (10).

Inflammatory toxins, produced by certain bacteria, can result in inflammation if too much of it enters the bloodstream from the gut. This can occur when the gut barrier is compromised, allowing bacteria and toxins to cross into the bloodstream.

Long-term immune system activation can cause inflammation, which is associated with brain and mental health disorders such as depression and Alzheimer's disease (11).

Probiotics, Prebiotics, and Postbiotics for Mental Health

Researchers have found that an imbalance in the gut's microbes called dysbiosis may contribute to depression, bipolar disorder, and schizophrenia, to name a few.

So, by extension, balancing the gut microbiome should help improve your mental health. And that is precisely what research on probiotics, prebiotics, and postbiotics shows.

Probiotics

The term probiotic refers to foods or supplements containing live microorganisms intended to maintain or improve the body's natural bacterial population.

Probiotics confer health advantages when consumed. But only certain ones affect the brain and mental health.

Probiotics that affect the brain have been dubbed "psychobiotics."

What are psychobiotics?

According to research published in Trends Neuroscience:

"Psychobiotics are beneficial bacteria (probiotics) or support for such bacteria (prebiotics) that influence bacteria–brain relationships. Psychobiotics exert anxiolytic and antidepressant effects characterized by changes in emotional, cognitive, systemic, and neural indices. Bacteria–brain communication channels through which psychobiotics exert effects include the enteric nervous system and the immune system (12)."

For example, specific probiotics, such as Bifidobacterium infants, have been shown to affect psychophysiological signs of depression and anxiety in rats. Indeed, the observed effects of specific probiotics on depression are so profound that researchers consider them comparable to antidepressant medications (13).

Similarly, studies suggest that the probiotic bacteria Lactobacillus helveticus NS8 may reduce anxiety (14).

Finally, one small study showed that the probiotic Bifidobacterium longum might ease the depressive symptoms of those with irritable bowel syndrome (IBS) when taken for at least 6 weeks (15). Anxiety or depression are common comorbidities of IBS patients.

Prebiotics

A prebiotic is a type of plant fiber that feeds beneficial microorganisms in the colon. These microorganisms metabolize and ferment the prebiotics to survive. So, prebiotics are essential for creating and maintaining a thriving and diverse microbial population that can help regulate moods and support mental health.

Additionally, bacterial fermentation of prebiotics also leads to the creation of postbiotic metabolites that support physical and mental health. (See the postbiotics section below.)

Specific prebiotics are being researched for their potential effect on psychological stress and other psychiatric disorders. For example, one recent study found that taking the prebiotic galactooligosaccharides for three weeks significantly reduced levels of the stress hormone cortisol in the body (16).

However, more research needs to be conducted to verify these results.

Postbiotics

Postbiotics are bioactive substances produced when the probiotic bacteria in the large intestine eat and break down fiber (prebiotics). Studies have found that postbiotics may have mental health benefits.

For example, research shows that the postbiotic version of Lactobacillus paracasei PS23 (PS23) can improve chronic anxiety and depression symptoms and reverse brain-derived neurotrophic factor (BDNF) levels in the brain's hippocampus (17). BDNF is a protein that impacts brain function and the peripheral nervous system.

The postbiotic metabolite butyrate has also shown promise in alleviating specific mental or mood disorders.

For example, studies suggest that butyrate may alleviate anxiety-related symptoms. In a different study, researchers found that increased beneficial bacteria in the gut microbiome, the type promoted by butyrate, dramatically reduced anxious feelings in those with chronic fatigue syndrome (18).

There is evidence that butyrate may benefit a number of neurological and psychological problems, including Alzheimer's disease, Parkinson's disease, stroke, Huntington's disease, and autism (19).

Diet and Mental Health

Now that you know about the brain-gut connection, you can use it to your advantage to improve your mental health. One of the best things you can do for your brain and your gut is to tweak your diet, as research shows that diet can support and improve mental health conditions.

Below are a few foods and nutrients that positively affect mood and mental state.

Fermented foods.
These foods contain live probiotic bacteria, such as lactic acid, that have been shown to affect brain activity (20). Fermented foods include sauerkraut, yogurt, cheese, kefir, and natto.

Fiber foods.
A high-fiber diet is essential for a healthy gut, body, and brain. Fiber helps balance your gut microbes and provides the postbiotic-producing bacteria needs. As mentioned above, prebiotic fiber can also reduce levels of the stress hormone cortisol (21). Great dietary fiber sources include oats, nuts, seeds, whole grains, fruits, and vegetables. Be sure to eat a variety of different fiber foods each day.

Omega-3 fatty acids.
An estimated 60 percent of the human brain is composed of fat, which your brain needs to maintain to function correctly. Unfortunately, the emphasis on low-fat or fat-free diets over the past few decades has degraded these levels. Fatty acids, which you must get through your diet, are essential to your brain's integrity. Indeed, according to human and animal studies, omega-3s can enhance beneficial gut microbes and lessen the risk of brain problems (22, 23, 24). The best omega-3 sources are found in fatty fish, such as salmon. Plant-based sources include chia seeds, brussels sprouts, flaxseed, walnuts, and hemp seed.

Polyphenol foods.
Polyphenols are plant-based compounds that are metabolized by gut microbes. Numerous studies show that polyphenols promote the growth of good gut bacteria and may enhance overall brain function and memory (25, 26). Foods rich in polyphenols include green tea, olive oil, coffee, and cocoa.

Tryptophan foods.
The body converts the amino acid tryptophan into serotonin upon consumption. Serotonin, known as the "happy hormone," is also a neurotransmitter and natural mood stabilizer. Rich food sources of tryptophan include turkey, cheese, and eggs.

What Foods Contain Butyrate?

There are no food sources that contain significant amounts of butyrate. For example, butter and other dairy foods contain only trace amounts of butyrate (butyric acid).

Since butyrate is primarily a postbiotic metabolite, you must get it by consuming high-fiber foods that can cause digestive distress if eaten in excess.

Can I Take Butyrate Supplements?

There are no pure butyrate supplements available on store shelves or online. Because butyrate is an unstable molecule, it dissolves before it ever reaches the large intestine, where it is needed to provide all the health benefits mentioned above.

Thus, butyrate is always produced in conjunction with a stabilizing ingredient, such as sodium butyrate, calcium butyrate, etc.

But there is no doubt that the BEST butyrate supplement contains TRIButyrate. It is a patented gut-healing super nutrient, which is time-released to deliver butyrate directly to your lower colon. This molecule is stabilized by combining a glycerol molecule with three butyrate molecules.

Final Thoughts

The gut-brain connection is a two-way communication system between the gut and the brain. Several factors, including your immune system, chemical messengers called neurotransmitters, and a direct physical connection with your vagus nerve, contribute to this process.
In addition, the gut microbiome plays an essential role in many of these processes, including regulating hormones, neurotransmitters, and proteins in the body.
Evidence suggests that your gut microbiome may influence mental health conditions such as anxiety and depression. Specific types of bacteria have been identified as being involved in this process.
Research shows that your gut health and your mood can be improved by eating high-quality foods, including those that contain probiotics and prebiotics.
You can also improve your gut microbiome and mental health by taking a butyrate supplement that contains TRIbutyrate.

Introducing: SANE Viscera-3 with Patented Gut-Healing TRIbutyrate

As mentioned earlier in this article, Butyrate is an important compound. A postbiotic metabolite is formed by the fermentation of fiber by bacteria in the lower colon. Several Ivy League doctors consider it to be the "optimal" one for gut health. In addition to helping to rebalance gut bacteria, it also acts to prevent inflammation within the digestive tract, repair and enhance the intestinal barrier, and support mental health.

Because Butyrate dissolves long before reaching the colon, you will not be able to find it in stores without a stabilizing agent added to it.

However, we have some good news to share with you!

As part of its partnership with health experts, SANESolution has developed the Viscera-3 Tributyrate POSTbiotic supplement, which consists of a patented, time-released form of butyrate (or butyric acid) which begins working immediately to improve gut and brain health.

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