The Truth About Gut Microbes & Probiotics

The Truth About Gut Microbes & Probiotics

  • Probiotics 101

  • By Desiree Nielsen, Registered Dietitian

    For those of us interested in gut health, we know there are trillions of bacteria living in our gut. We're also familiar with the fact that our community of gut bacteria are influenced by their environment: stress, smoking, diet and medications.

    But just who are these microbes? How did they get there? Where exactly do they live? And what’s the deal between resident and transient strains?


    Your Gut: A Community of Microbes

    The bacteria that live in your gut are known as your resident strains. They are selected by your genetics, your early environment and your lifestyle. From birth (your first exposure to microbes) through to about the age of three, you are building your core of resident microbes – they will be as unique to you as your fingerprint. While many bacterial strains are common amongst lots of humans, there are plenty of individual strains that may be abundant or utterly absent from person to person.

    You may also be surprised to learn that within your gut is a variety of local ‘neighborhoods’ that attract different communities of bacteria. Your gut looks like a vast, velvety carpet that is, in fact, a series of folds and micro-folds that create a complex surface for the absorption of nutrients. On top of the gut cells is a thick layer of beneficial mucus. Nestled into the mucus is one community of bacteria; deep in the folds between the gut cells is another. The community of bacteria in your mouth looks different from the community in your small intestine, and the community in your ascending colon looks different from the community in your descending colon.


    Tourists Welcome!

    Of course, these resident microbes aren’t the only ones in town. There are also transient bacteria that are just as they sound - temporary visitors. Typically introduced through intentional or unintentional consumption, these transient bacteria can impact the resident community for better – or worse. Think about the difference between eating some yummy fermented sauerkraut versus getting hung up with food poisoning on vacation.

    When it comes to probiotics, there is a bit of misinformation about the concept of transient vs resident strains. Often, the terms are used to distinguish between human-origin strains (resident) and soil- or dairy-origin (transient) strains. And technically, all human strain probiotics have the potential to become residents; they were someone’s resident strains at one point! However, if you are consuming these bacteria strains, then by definition, you are consuming transient strains, even if they are human in origin.

    Your resident population actively resists colonization by transient strains; however, if your probiotics are human strain, there is more likelihood that they will be successful in staying at least a few days. This success depends on many factors, like the local gut environment and the strength and robustness of the transient strains. There is zero guarantee that even a clinically proven, effective human-strain probiotic can permanently re-colonize your gut flora. Finding this magic formula would be worthy of a Nobel Prize!

    So how do transient strains have an impact? You can think of this interaction like the resident and tourist population of a city. The tourists do function as a part of the community, seeing the sights, eating the local food and interacting with the residents, but they are variable and changeable over time.


    So, Does Taking a Probiotic Work?

    Transient, probiotic human strain bacteria can have many beneficial effects on the human microbiota: they can temporarily supplement the function of your resident bacteria that might be diminished due to poor diet or antibiotic use. Transient strains can positively interact with your immune system and your nervous system. Transient strains can also compete with potentially harmful bacteria to prevent their growth – or, it is possible that transient strains can even stimulate the growth of your resident bacteria.

    To understand this, you have to understand a bit about what bacteria need to thrive. Each strain has its preferred food – and when it ferments that food, it produces other new substances. So transient strains can help increase the food available for residents and support their growth (like how tourism can stimulate the local economy). We have seen this in the literature, with probiotic Lactobacillus bacteria helping increase the growth of beneficial residents like Bifidobacterium. So why are human strain probiotics important? We take human strain probiotics that are research-proven to stimulate a beneficial change in your digestive system and facilitate an optimal environment for your own resident strains to grow.

    Bio-K+ is a synergistic formula containing three different human-strain bacteria: Lactobacillus (L.) acidophilus CL1285®L. casei LBC80R® and L. rhamnosus CLR2®Bio-K+ has been clinically proven to help fight off pathogenic bacteria like E. coli and C. difficile – important for supporting your resident flora in times of antibiotic use. The strains in Bio-K+ produce lactate, a natural organic acid that lowers the pH of the gut that can feed resident strains and produce a beneficial environment for their growth.

    One of the most common questions we receive about Bio-K+ is how much to take. One full bottle of drinkable Bio-K+ daily is the clinically proven dose for acute issues like antibiotic use. If you have milder digestive issues, take a half bottle daily and for general health, just a quarter bottle a day is all you need.


    Like any ecosystem, a healthy community of gut bacteria is dependent on diversity. But that diversity is built on the interaction of your resident microbes and the transient bacteria you introduce through consumption. Taking a probiotic daily, like Bio-K+, can help your resident community thrive.

    Do you have more questions about gut health? Let us know in comments below! For more information on probiotics, Bio-K+ and digestive health, join our community. Click here to find the closest point of sale. Contact us or find us on Facebook and Instagram.




    Zhang, Chenhong et al. “Ecological Robustness of the Gut Microbiota in Response to Ingestion of Transient Food-Borne Microbes.” The ISME Journal10.9 (2016): 2235–2245. PMC. Web. 29 Mar. 2018.


    Scott, Karen P. et al. “Manipulating the Gut Microbiota to Maintain Health and Treat Disease.” Microbial Ecology in Health and Disease 26 (2015): 10.3402/mehd.v26.25877. PMC. Web. 30 Mar. 2018.


    Derrien, Muriel, and Johan ET van Hylckama Vlieg. "Fate, activity, and impact of ingested bacteria within the human gut microbiota." Trends in microbiology 23.6 (2015): 354-366.

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    Desiree Nielsen Registered Dietitian
    About the author
    Desiree Nielsen is a registered dietitian, author and host of the vegetarian cooking sshow, The Urban Vegetarian. Desiree takes an evidence-based, integrative approach to her dietetics work, with a focus on anti-inflammatory, plant-centredcentered nutrition and digestive health.
    View all articles by Desiree Nielsen
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