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Prebiotics, Probiotics, POST-biotics

Written by Dr. Jewel Alfoure, ND

Prebiotics, Probiotics, POST-biotics

  • Gut bacteria play a role in nutrient assimilation

  • There are more bacteria than human cells in the human body

  • Our energy creation powerhouse may be probiotic in origin

Gut bacteria determine much more than gut health and can extend in their functionality from nutrient assimilation to healthy aging and overall body maintenance.

It is almost hard to believe that our bacterial flora outnumbers our human cells. Some researchers propose that the ratio of bacterial to human cells is 1 to 1. Other researchers, however, propose that  the ratio is closer to 1 to 10. In many ways, we are more bacteria than we are human (1). 

Additionally, those bacterial cells do not just outnumber us, they have also made deals to penetrate deep into our cells and act as power houses. 

Theories and genetic analysis demonstrate that our most efficient energy powerhouse, the mitochondria, is also of probiotic origin (2). 

Further, theories demonstrate that our energy metabolism buddies (mitochondria) communicate with our gut microbes and that many of the signals that help the body function optimally fall under the category of POST-biotics (3,4).

Probiotics - Natural flora that keep us healthy in exchange for food and shelter

Prebiotics - The food that we consume that goes to feed the healthy part of our gut flora 

Note: high sugar foods should NOT be called prebiotics. While they do feed bacteria, they tend to feed pathogenic and unhealthy bacterial colonies. Thus, creating more competition and making it harder for healthy, gut-maintaining bacteria to thrive (5). 

POSTbiotics - Metabolites that are made by healthy bacteria that signal actions that are conducive to overall health.

That Gut Feeling: When Bacteria Take Over Your Emotions!

  • Depression and anxiety are linked to inflammatory levels

  • Probiotics play a role in maintaining low inflammation
  • The gut directly sends signals to the brain though Cranial Nerve X (Vagus Nerve)

Profoundly, it was found that probiotics play a direct role in maintaining healthy inflammatory metabolite levels.

Keeping in mind that depression and anxiety are directly linked to inflammation, it was found that some strains of healthy bacteria play a direct role in alleviating symptoms of depression and anxiety (6). 

Probiotics do not just impact the production of mood promoting substances, there is evidence that they can produce their own signalling molecules and neurotransmitters. 

Neurotransmitters are a type of  signaling chemical that the brain uses for sending signals that translate as emotions (6,7,8). 

What Happens in Vagus?


  • A Special nerve in the body is responsible for sending gut-brain signals

  • Probiotics have the power to directly as well as indirectly impact mood
  • Gut feelings are real manifestations of gut-brain communication

The human body has a long cranial nerve known as The Vagus Nerve. The vagus nerve is a nerve that runs through the neck to the brain. 

It has branches that run from the brain stem all the way down to the walls of the digestive system.

It plays a role in the autonomic nervous system which is the branch of the nervous system that is automatic in nature.

It governs all the actions that we do not have to think about including breathing and digestion.

In the case of digestion, some of the digestive metabolites, including the POSTbiotics that can send signals directly to the brain stem though the vagus fibers that are embedded in the walls of the gastrointestinal system (9). 

Many would attest to the feeling of butterflies in the stomach when one is stressed.

Stress contracts the digestive system and shunts the blood into other tissues of the body. 

That process of focusing on the Sympathetic branch of the autonomic nervous system, disrupts the flow of data through the vagus nerve (10). 

When the vagus nerve is not sending signals to the brain, all the anti-inflammatory molecules signaled to be made are not released. 

In return, the gut suffers negative consequences that even extend to the breakdown of the integrity and the diversity of the probiotic flora (11).

Guts are NOT Supposed to be Leaky 

  • Leaky gut is a phenomenon of bacterial dysbiosis

  • Inflammatory markers increase with leaky gut

  • Low grade inflammation directly impacts neurotransmitter synthesis 

There are even theories that the increase in the permeability of the gut lining, known as Leaky Gut Syndrome may be related to bacterial dysbiosis (12).

Probiotics keep the integrity of the gut lining which in return makes it easier for the metabolites produced by the healthy gut bacteria to reach the brain.

Digestive metabolites, on the other hand, when leaked into the blood promote inflammation and make it harder for the signal from the gut to reach the brain 

There are even some studies that demonstrate that healthy gut microbes have the capacity to modulate neuroinflammation through the previously explained pathways (13,14)

What Makes a Good Probiotic Supplement?

  • Building probiotic diversity can be done as experiencing the most joyful aspects of life

  • Prior to considering introducing healthy bacteria, it is best to prepare an environment that maintains healthy bacteria by eliminating the intake of food that feeds unhealthy strains

Naturally, the act of daily living accumulates probiotics sufficiently enough for us to have diversity in our guts.

Perhaps the joyful interactions of life are some of the most important builders of our gut diversity. Some actions that we may not think about can contribute positively to the diversity of our body flora. Those actions include gardening (bare hands), touching our loved ones, sexual contact,  interacting with pets and even handling our own uncooked food to prepare it.

Studies show that dog owners have more diversity in their gut flora, for example. Thus, it is important to choose our battle and think twice about living an isolated, highly sanitized life.

In addition, building a healthy gut flora can be achieved through the continuous influx of probiotic rich foods that include fermented foods, high soluble-fiber foods and foods that are high in complex carbohydrates, in general. 

What may be more important than having foods high in probiotics and probiotics is refraining from foods that will end up turning into fuel for unhealthy competing microorganisms. 

High sugar foods, for example, do turn into food for bacteria, but not the healthy types, thus they end up smothering the healthy bacteria with competition and toxic metabolites. 

Some gut protection factors including N-acetylglucosamine may contribute to building a healthy gut. A healthy gut is one that is less inflamed and less likely to smother healthy bacteria with inflammation (15).

N-acetylglucosamine and The Gut (16)

  • Structural component of cell surface

  • Key component of peptidoglycan

  • Has roles in cell signaling

  • Expression changed by unhealthy flora

  • Regulates intracellular proteins

  • Regulates inflammation 

  • Used for osteoarthritis 

  • Inflammatory bowel disease ameliorating agent 

Though it is always good to have the body choose the bacteria that is most suited to colonize internally. Each bacteria can have different functions and benefits. Bifidobacterium species for , example, are a common healthy gut bacteria and feature the following benefits:

Our Buddy Bifidobacterium- General Species Features 

  • Produce short- chain fatty acids- interact with gut serotonin production cells 

  • Produce acetate- gut acidity promoting

  • Feeds gut bacteria Eubacterium who make butyrate

  • Serotonin enhancing the brain and in the gut 

  •  Antimicrobial activity against:

    • Listeria monocytogenes- Common food bacteria (may be critical to some) 

    • Clostridium perfringens- Common food poisoning bacteria

    • Escherichia coli - Common UTI bacteria (17,18, 19)

What Makes a Good Probiotic Supplement?

A good probiotic supplement is one that is most suited to the needs and the lifestyle of the individual seeking probiotics.

For example, a probiotic that is needed after a course of antibiotics may be different from one needed for gut health maintenance.

While both probiotics are meant to colonize the gut, a post-antibiotic probiotic is more about diversity and the introduction of species that may have completely been wiped out by the antibiotic.

On the other hand, a good gut probiotic is one that contains the strains that stimulate the secretion of gut-protective mucus and that produces metabolites that can be used as food by other bacteria.

Needing a very high colony probiotic constantly is a sure sign that the gut is killing off the healthy probiotics.

It is also important to note that some individuals with sensitive guts or with issues like Irritable Bowel Disease and Ulcerative Colitis may react poorly to some strains. An aggravation of a serious gut illness may result in significant symptoms.It is always important to consult a healthcare practitioner and start with more reasonable doses of probiotics (20). 

Healthy Probiotic Strains to Look for:

Bifidobacterium bifidum (21, 22)

  • Phytochemical- modifier of gut microbial profile 

  • Immunomodulatory

  • Suppresses allergic response

  • Anti-inflammatory in bowel disease

  • Eczema suppressing

Bifidobacterium longum (21, 22, 23)

  • Benefits irritable bowel syndrome

  • Reduces depression

  • Improves quality of life

  • Changes brain activation patterns

  • Reduces limbic reactivity- Brain relaxing

Lactobacillus acidophilus (24, 25, 26)

  • Immunomodulatory effects

  • Make precursor to GABA - Relaxing neurotransmitter 

  • Antagonistic against pathogens

  • Anti-tumor

  • Preserves Intestinal Barrier


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