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  • Writer's pictureBrooke Evans

Prebiotics, Probiotics, and Psychobiotics - Your Essential Guide

Probiotics and prebiotics have become extremely popular in recent years. Only second to vitamins and minerals supplements, more Americans use probiotics or prebiotics than any other nutritional supplement (1).

And there is good reason for this. Because of the increased research, gut health is now considered to be a key pillar of overall physical health, but more recent studies have shown that the gut influences mental health as well. These psychobiotics have been shown in preliminary research to provide the user with mental health benefits, stemming from the gut. 

Probiotics and prebiotics promote health in many ways. For example, a gut full of “friendly” or beneficial microbes absorb more nutrients, discourage harmful microbes, and can even reduce inflammation—all of which are beneficial to gut health and your overall health and wellness. Even though supplements are what we typically think of when we think about probiotics, both pre- and probiotics can be found within the food we eat, as well.

The Catalyst Nutrition and Training team has prepared this guide to prebiotics, probiotics, and psychobiotics to educate you in what they are and how they interact with your body.

What are probiotics and prebiotics? 

Before we dive into the ways that probiotics, prebiotics, and all the other “biotics” can impact our health, and how to get enough of them, here are some definitions to reference:

  • Microbiome - The large intestine of your digestive tract is home to trillions of helpful microbes that naturally inhabit this area (2,3,4). Most of these microbes are bacteria, but some health-promoting viruses and fungi also live within your intestines. When we put all of these organisms together, they create the microbiome. Everyone starts with a unique microbiome at birth, and this is influenced by what we eat, what supplements and medications that we take, and our lifestyle choices (2,3).

  • Probiotics - Probiotics are “live microorganisms that are intended to have health benefits when consumed or applied to the body” (1). The word comes from the Greek words “pro” and “bios” meaning “for life” (4).

  • Prebiotics - Prebiotics are “nondigestible food components that selectively stimulate the growth or activity of desirable microorganisms” (1). They act as food for the microbes in your gut and are an essential part of growing a diverse, thriving microbiome (3,5). 

  • Psychobiotics - Psychobiotics are “probiotics that confer mental health benefits” (6).

microorganisms that make up gut health

Health Benefits of Pro-, Pre-, and Psychobiotics

Finding and maintaining gut microbiome balance provides a myriad of health benefits. The list of positive health effects of a healthy gut is growing rapidly as more and more research is done. To name just a few, these benefits include improved digestion, increased production of essential nutrients, improved immune system, improved moods and mental health status, and even reduction of bodily inflammation and toxin-producing microbes (1,3,7).

Today, we are focusing on how the balance affects gut and mental health.

Gut Health

The microbiome helps maintain and improve gut health in many ways. It contributes to healthy bowel function and may help with conditions such as colitis, which is inflammation of the inner lining of the colon (1,2). Some studies show that probiotics can help with diarrhea and constipation (1), especially if the cause is due to an imbalance in the gut microbiome (8). 

How does the gut microbiome help us achieve a healthy gut? There are a myriad of ways. First of all, certain microbes can produce health-promoting nutrients, such as short-chain fatty acids and some B vitamins (4). These nutrients are then absorbed by our cells and nourish other areas of our bodies. Other substances produced by gut microbes help to lower the pH of that part of the gut and reinforce the intestine’s lining (9). The nutrients that the gut microbiome produces can also reduce inflammation, eliminate toxins, as well as boost the body’s ability to absorb essential minerals (4).

Mood, Mental Health, and Psychobiotics

Nutritional psychiatry is a rapidly growing topic of research, which focuses on the links between what we eat and how we feel both mentally and emotionally (7). Many studies have shown the strength of this food-to-mood connection. For example, eating a high-quality, nutritious diet nourishes the brain, helps keep inflammation down, and helps to stabilize our mood throughout the day (7). Additionally, many chronic gut conditions are often accompanied by mood disorders such as depression and anxiety (6). As we discussed above, there is a subgroup of probiotics that have mental health benefits called “psychobiotics” (6).

The BMJ Nutrition Prevention & Health journal published a recent study consisting of seven clinical trials that found certain probiotic supplements were linked to “measurable reductions in depression”, even without the use of prebiotic supplements (10).

But how can gut health influence our minds and emotions? Via the “gut-brain axis.” Quite a few parts of this axis foster constant communication in both directions between your gut and brain (6). The Gut-brain axis includes:

  • Some neurotransmitters and neurohormones are produced in the gut. For example, it’s estimated that the gut produces 90-95% of the serotonin in the body (6,7). Serotonin is the neurotransmitter that helps our bodies regulate sleep, appetite, and emotions, and manage pain (7). 

  • The digestive system contains 100 million nerve cells, making it a hub for the immune system (7)! 

  • A healthy gut microbiome can help regulate the stress response and inflammation throughout the body (6). 

  • Some studies done with mice suggest that the gut microbiome can influence levels of brain-derived neurotrophic factor (BDNF) in the central nervous system, which in turn impacts behavior (6).

All of these gut-brain activities are influenced by the gut microbiome and pro- or psychobiotics (6,7).

a healthy gut can benefit your overall health in numerous ways

How to Get Enough Probiotics and Prebiotics 

In addition to store-bought supplements, we can get both pre- and probiotics from the food we eat!

Probiotic Foods

Fermented foods, which are produced with the help of bacteria, are some of the foods that can help us achieve a healthy gut! Fermented foods include yogurt, kefir, pickles, sauerkraut, miso, kombucha, and more (2). It’s important to know that not all fermented foods will still contain live active cultures of healthy bacteria by the time you purchase them from the store and consume them (2,9).

The best option is to select fermented foods from the refrigerated section (3) and make sure the product label reports “live active cultures” in the food (2). If you know your way around the kitchen, fermenting your own foods will also ensure you are getting the most healthy bacteria available! Some companies are now fortifying unfermented foods, like cereals and juices, with probiotics (9). Remember to read the nutrition labels!

certain foods are packed with more gut-healthy bacteria than others

Prebiotic (Fiber-Rich) Foods

Fiber-rich foods, particularly insoluble fiber, provide the fuel that gut microbes need to thrive. Foods such as oatmeal, whole grain bread and pasta, asparagus, leeks, onions, sweet potatoes, corn, bananas, beans, and lentils all provide the prebiotics needed for a healthy gut. Include a variety of these fiber-rich foods to boost the biodiversity of your microbiome (3) naturally.

In addition to fueling our gut with healthy bacteria, it’s also important to limit the intake of foods that could deplete your healthy gut microbes. Sugars, artificial sweeteners, saturated fats, and heavily processed foods can negatively impact our gut health, so minimizing our intake will help maintain the healthy gut we are trying to build (2,3)!

whole foods are best for acquiring guy-healthy bacteria

Probiotic Supplements

There are many strains of bacteria available in probiotics, each having unique effects. The most common strains found in probiotic supplements include Lactobacillus, Bifidobacterium, Saccharomyces, Streptococcus, Enterococcus, Escherichia, and Bacillus (9). Many (but not all!) of these strains are similar to the bacteria found naturally in the gut microbiome (1).

Supplements combine different strains of bacteria and yeasts in different amounts to create many unique supplement products to choose from. 

Supplement ingredients, even in probiotics, are not regulated in the United States like food is, and some products have been found to provide fewer or different probiotics than what is listed on the label (8). When choosing a probiotic, make sure you select a high-quality product to ensure you receive the bacteria you are paying for!

If you need some help choosing a high-quality product, we recommend the FloraMend Prime Probiotic supplement from Thorne. This is a trusted brand and a perfect everyday probiotic supplement!

Note that probiotic supplements should not be given to premature infants or people with severe illnesses or compromised immune systems without a recommendation from a qualified healthcare professional, as there have been reports of harmful effects (1).

Prebiotic Supplements

Prebiotic supplements contain starches that the gut microbes use as fuel to metabolize into beneficial compounds. These fiber-rich supplements include inulin, GOS (galactooligosaccharides), FOS (fructooligosaccharides), and lactulose (4).

A prebiotic supplement can help keep your gut microbiome up and running! Along with your probiotic supplement, using FiberMend prebiotic supplement from Thorne will support the healthy gut you are building!

Final Thoughts on Pre- and Probiotics

Gut health is MORE than just a well-functioning digestive system. Gut health influences every part of our health - both physical and mental.  The most important thing that you can do to foster gut health is nourishing and fueling your gut’s microbiome. This includes consuming probiotic (fermented) foods as well as prebiotic (fiber-rich) foods. When food just isn’t cutting it - both probiotics and probiotics are available in supplement form. Just be sure to choose high-quality sources, for both food and supplements!

Do you need help optimizing your gut health or overall health? Catalyst Nutrition and Training would love to help! Registered dietitian nutritionists help their patients in so many ways, including supporting you on your gut health journey.


  1. National Center for Complementary and Integrative Health. (2019, August). Probiotics: What You Need To Know.

  2. Harvard Health Publishing. (2022, November 14). Probiotics and prebiotics: what’s really important?

  3. Corliss, J. (2023, November 1). How a healthy gut helps your heart. Harvard Health Publishing.

  4. Ji, J., Jin, W., Liu, S. J., Jiao, Z., & Li, X. (2023). Probiotics, prebiotics, and postbiotics in health and disease. MedComm, 4(6), e420.

  5. Golen, T & Ricciotti, H. (2021, November 1). What are postbiotics? Harvard Health Publishing.

  6. Del Toro-Barbosa, M., Hurtado-Romero, A., Garcia-Amezquita, L. E., & García-Cayuela, T. (2020). Psychobiotics: Mechanisms of Action, Evaluation Methods and Effectiveness in Applications with Food Products. Nutrients, 12(12), 3896.

  7. Selhub, E. (2022, September 18). Nutritional psychiatry: Your brain on food. Harvard Health Blog.

  8. Harvard Health Publishing. (2022, February 2). Should you take probiotics?

  9. Office of Dietary Supplements. (2023, November 3). Probiotics: Fact Sheet for Health Professionals.

  10. British Medical Journal. (2020, July). Probiotics alone or combined with prebiotics may help ease depression.

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