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Nurture Your Gut: The Essential Guide to Probiotics

Nurture Your Gut: The Essential Guide to Probiotics

The first usage of probiotics to benefit human health dates back to over 100 years ago! Our knowledge around the vast benefits that probiotics potentially provide continues to expand. To date, a quick PubMed search for titles involving “probiotics” and “human” health revealed 5,376 research studies!

Gut health and the human microbiome have become topics of exponential interest, and more people than ever before turn to probiotic supplements as a way to reap the potential benefits. But where do you start when sifting through all of the information out there?

In this post, we’ll explore the definition of probiotics, learn about how they work, where they come from, and roles they play in human health based on currently available research. We’ll also discuss how to navigate the market and information out there to best serve your personal health journey.

What are probiotics?

To set the stage, let’s start with an understanding of what makes a food or supplement a probiotic. The International Scientific Association for Probiotics and Prebiotics defines a probiotic as follows:

Probiotics are “live microorganisms which, when administered in adequate amounts, confer a health benefit on the host.”[1]

We can see that there are three noteworthy points to this official definition:

  1. Probiotics are live microorganisms - Most probiotics are bacterial species (such as Lactobacillus and Bifidobacterium), while some are yeasts (such as Saccharomyces). It is estimated that there are at least as many, if not more, bacterial cells within each of us than there are our own cells that make up our own bodies. Most probiotics are bacterial species that normally colonize our gut microbiomes.[2]
  2. Probiotics must be administered in adequate amounts - This is an important point that mirrors that of many food-first and nutraceutical products. For them to exert an effect or their supposed benefit, proper dosing is very important. You wouldn’t take 1/100 of a painkiller and expect your headache to go away, would you?
  3. Probiotics provide a health benefit for the host - The benefits that probiotics offer span a wide variety of our body systems from our digestive health to immune health and beyond. It’s important to choose products that have documented, researched benefits as some products market strains that may be untested or unverified.

The Role of Probiotics in Health

As the research continues to explore the effects that probiotics have on our health in many areas, it’s important to keep in mind that each of our 8.1 billion human microbiomes on this planet are unique.

Research has teased out some relationships between certain strains of probiotic organisms and the effects that they have in the general population. There is also much that we have yet to learn. Here are some of the most common documented benefits of probiotics with links to supportive research!

Evidence-Based Benefits of Probiotics

These are just a few of the available research highlights that are systematic reviews of the currently available research! Did any of these benefits surprise you?

How do Probiotics Work?

Considering how many different conditions and body systems can potentially benefit from probiotics, you might wonder about how they work! The microbiome is a fascinating, complex, and ever evolving system within us.

Just as each of the 8.1 billion human microbiomes are unique in their composition, some of the mechanisms of how probiotics work are also highly individualized.

Originally, it was thought that if you take a probiotic supplement, it then “seeds” your microbiome with those strains of bacteria. It was thought that after they were colonized, they exert their many benefits. It turns out that this likely isn’t the most accurate picture.

Instead, it is generally accepted that probiotics are more transient in most people. You can think of them as visitors, tourists even, who spend their currency in the form of health benefits and then exit the picture. It is important to note that colonization of probiotics is likely not necessary for probiotics to work and exert their positive benefits!

Some of the benefits are species and strain-specific, while other benefits are more global in nature. Here are 4 main ways that probiotics likely work based on current research:

  1. Interacting with the immune system in the gut lining
  2. Interacting with normal and pathogenic microbes to promote balance
  3. Generating beneficial waste products, including vitamins and nutrients like anti-inflammatory short-chain fatty acids (SCFA’s)
  4. Communicating with our body cells through chemical signals, including our brain and nervous system

There are other strain-specific mechanisms by which some probiotics work including neutralizing toxins, breaking down our bile salts, and more.

Sources of Probiotics

Probiotics come from two primary sources: food and supplements. What we eat has the dramatic potential to influence the vitality and diversity of our microbiome. This includes probiotic foods, often fermented products, which used to be much more common in our diets before refrigeration and the development of the Standard American Diet (SAD).

Food Sources of Probiotics

  • Yogurt and Kefir (preferably homemade or non-conventionally made with no added sugar)
  • Sauerkraut
  • Kimchi
  • Pickled vegetables and products
  • Miso and Tempeh (fermented soy products)
  • Kombucha
  • Fermented teas such as Pu-erh

Tips For Choosing Probiotic Supplements

Rather than discussing all of the different strains and blends of probiotics out there in the supplement market, let’s talk practical tips when navigating the probiotic world.

  • Considering the transient nature of probiotic supplements, a blend of researched and evidence-based strains is a great way to find a daily gut health supplement.
  • Look for quality sourcing and production when choosing a supplement such as GMP (good manufacturing practices) certification. I recommend trying Horizon.
  • When looking for condition-specific supplements, use reputable websites and research centers such as PubMed or the World Gastroenterology Organisation, a few of my favorite go-to resources.
  • Don’t get too caught up in CFU (colony forming units) or the number of bacteria present per serving. More is not always better.
  • Consult a health professional if you’d like guidance on specific quality supplements or comprehensive stool testing.

Safety and Potential Side Effects of Probiotics

All in all, probiotics in both food and supplemental sources are generally considered safe and well-tolerated by the general public. Considering their effects on the immune system and interacting with the microbiome, the most common side effects are related to an immune system response or digestive symptoms.

Potential side effects of probiotics include:

  • If you do experience side effects from a probiotic food or supplement, here are a few things to consider.
  • First, reach out to wellness provide familiar with probiotics, specific strains, and their usages to see if the supplement is the right fit for you.
  • You might consider a different blend or different dosage.
  • Consider that there may be an underlying imbalance in your microbiome that you might want to address before stimulating the immune system and nervous system with probiotics.
  • Side effects may be temporary as your microbiome and immune system adjust and react to a new supplement. Remember, quality supplements are very real, concentrated signals that can influence our health and stimulate an effect.


As we finish our exploration of probiotics, it becomes evident that these microbes offer multifaceted benefits for human health, ranging from digestive support to mental well-being.

We have traced the historical origins of probiotics and surveyed the expansive and ever-growing body of contemporary research, which underscores their relevance in modern, integrative healthcare.

Navigating the vast probiotic products available is no doubt noisy and requires a judicious approach informed by evidence-based practices and personalized considerations. By reading this introduction to probiotics, I hope that you feel more comfortable making informed decisions, seeking out reputable sources, and knowing when professional guidance might help. I also encourage you to stay connected with Cielo and myself, Dr. Kenny, for more evidence-based explorations of key pillars of holistic health!

About the Author

Dr. Kenny Mittelstadt, DACM, DC, L.Ac., Dipl.OM.

Kenny Mittelstadt is a functional health practitioner and acupuncturist based in San Antonio, Texas. He is trained through the Institute for Functional Medicine and received both of his doctorate degrees with highest honors from Southern California University of Health Sciences. He focuses on empowering patients through wellness education and root-cause healing – transforming health through personalized, lab-based functional medicine programs!


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