Probiotics 101


The World Health Organization defines probiotics as “live microorganisms that, when administered in adequate amounts, confer a health benefit on the host.” While there are probiotics for the skin (applied topically) and the mouth, the vast majority of probiotic products out there target the intestines. [1]

The typical adult has around 40 TRILLION bacteria and yeast inhabiting their small and large intestines. By comparison, we have around 30 trillion cells in our entire body. These 40 trillion intestinal critters make up what we call the gut flora, also called the gut microbiome or gut microbiota. The average adult’s gut flora weighs about 3.5 pounds, which is actually heavier than the average adult's brain! [2-3]


The condition of the gut flora has been tied to roughly 90% of the diseases that we deal with here in the United States, so it’s an understatement to say that taking care of your GI tract and gut flora is important! [4]

Probiotics are an important tool in the gut health toolbox, and with probiotics we have two broad options: one is to get probiotics through food, and we can also get probiotics through nutritional supplementation...


There are a few food items that do contain notable amounts of probiotics per serving, including cultured veggies like raw/unpasteurized kim chi and sauerkraut, the fermented tea kombucha, and yogurt and kefir (the latter of which is a drinkable type of yogurt).

Cultured veggies are a great dietary addition for most people. While the occasional kombucha is fine, I do caution people against habitually drinking them due to kombucha's very low pH levels and the damage that can cause to tooth enamel. With yogurt and kefir I generally suggest high quality goat or sheep’s milk products instead of cow’s milk options, due to the smaller molecule size and digestive issues with A1 beta casein protein, which is found in most cow’s milk products but is not present in sheep or goat’s milk products. If a person is highly sensitive to all dairy I'd advise they avoid yogurts and kefirs, at least temporarily, or try a coconut kefir instead (made with either coconut water or coconut milk). [5-6]


With probiotic supplements, the conversation can get complex but I’ll try to keep it as simple as I can. As far as probiotic strains go, lactobacillus and bifidobacterium strains dominate. You may also see probiotic supplements containing bacillus bacteria strains as well as saccharomyces yeast strains.

Broadly speaking, lactobacillus strains tends to be helpful for small intestinal and renal issues, whereas bifidobacterium strains tend to support the large intestine or colon, but there’s plenty of crossover here. Bacillus strains, which are sometimes called Soil Based Organisms or SBO probiotics, may be particularly helpful for those battling SIBO (Small Intestinal Bacterial Overgrowth), who otherwise have trouble tolerating more conventional probiotic formulations. And saccharomyces yeast probiotics, like those containing s. boulardii, have been clinically shown to improve intestinal barrier functioning, reduce inflammation and modulate the immune system. I do advise a little more caution with s. boulardii probiotics, as fungemia, which is an overgrowth of yeast, can occur in certain situations and at certain dosages. [7-9]


For the majority of my clients I suggest a higher dose lacto and bifido probiotic containing some of the more rigorously studied strain types, such as l. acidophilus, l. rhamnosus, l. casei, l. plantarum, l. gasseri, l. reuteri, b. lactis, b. bifidum, b. breve, b. longum and b. infantis.

A common therapeutic dosage range might be 25-100 Billion CFU, 1-3 times a day (CFU stands for colony forming units). A 2010 study from the American Journal of Gastroenterology that looked at more than 250 adults dealing with antibiotic and c-diff associated diarrhea found that a dosage of 100 Billion CFU per day of a lactobacillus probiotic was significantly more effective than 50 Billion CFU/day. For those dealing with more acute and serious health situations, the therapeutic dosage may be even higher. For instance, at least two randomized controlled trials have used dosages up to 3.6 TRILLION CFU per day on study participants battling mild to moderately active ulcerative colitis, with excellent results. [10-11]


So which probiotic supplements are my favorites? As of March 2021 I’d say these 3 make the cut...

* Now Foods 100 Billion CFU (capsules)

* Renew Life 90 Billion CFU (capsules; preferably the women's formula)

* Healthy Origins 30 Billion CFU (capsules)

All three of these companies are offering high-quality, higher dose probiotics that contain a blend of clinically backed lacto and bifido strains. Again, I’d suggest picking up one containing a minimum of 25 billion CFU per capsule.


Today I’m not deep diving into what the clinical data says on which health conditions probiotics have been shown to benefit, but reviews like one from 2018 in the Journal of Clinical Pharmacology show that some of the strongest evidence is for the use of probiotics in preventing or treating conditions like colitis, diarrhea, acute respiratory infections and infant colic. Other studies have shown probiotics useful for treating constipation, IBS, obesity, various skin conditions, immune system-related issues (including cancer and COVID-19), brain health (including mood disorders) and inflammation (including joint pain and arthritis). [12-20]


In talking about probiotics, gut flora and intestinal health I think its important to mention that gut health is influenced by SEVERAL factors. While probiotic supplements and foods can be valuable tools in the fight to restore or maintain optimal gut health, don’t expect a probiotic supplement or drinking some kombucha or eating yogurt to solve all of your digestive woes, especially if you have other factors that are working to impair optimal gut functioning. [21-22]


If you want to test the condition of your gut flora, in my opinion the current gold standard test is the GI Map stool test produced by Diagnostic Solutions. This test is a bit spendy, and in my experience insurance often doesn’t cover the cost of the test (that's another rant altogether- how mainstream medicine almost always neglects testing the gut microbiome and how almost every health insurance plan won't cover these tests).

Rant aside, this is a fantastic test if you want information on which intestinal parasites, bacteria, yeasts and viruses you may be dealing with. It also has markers for occult (hidden) blood, fecal fat and pancreatic enzymes. If you want a less comprehensive (and cheaper) test that focuses more on gut bacteria, microbiome tests like those made by Psomagen (Gutbiome test) or Thryve (Gut Health test) may be good options for you. Both are available to order on Amazon.


If you're ready for a significant, positive health change and want to take a holistic, personalized, evidence-based approach to get there, let me know! I provide health and nutritional consulting as well as personal training services to both local (Charleston, SC area) and remote clients. Email me at to find out more today.


1 (2005 article on probiotics)


3 (2004 book on Probiotics)


5 (2008 study on acidic beverages & tooth erosion)

6 (2015 study on milk intolerance, including lactose & beta casein proteins)

7 (2020 study on lacto & bifido strains for small intestinal conditions)

8 (2014 study on SIBO using bacillus probiotics)

9 (2019; s. boulardii has anti-inflammatory effects and preserves & restores intestinal barrier function)

10 (2010 study of antibiotic-associated diarrhea and c.diff-associated diarrhea showing superiority of 100B CFU vs 50B CFU)

11 (2013 article; discusses VSL #3/visbiome and using up to 3.6T CFU in clinical studies)

12 (2018; review found 68% of probiotics reviewed had strong-moderate efficacy for at least 1 type of disease)

13 (2018; 4 significant conditions have consistently been shown to respond to probiotics in humans in meta-analysis: NEC, IBS, infant colic & respiratory infections)

14 (2018; probiotics confer immunological protection to the host through the regulation, stimulation, and modulation of immune responses)

15 (2020 review on the efficacy of probiotics for treating various skin conditions)

16 (2010 review on probiotics effect on cancer incidence and treatment; "There are several epidemiological evidences that support a protective role of probiotics against cancer.")

17 (2020 review of probiotics & COVID; "we (the authors) believe that the administration of probiotics will help in boosting the host-immunity, and similar to other anti-viral studies it might reduce the symptoms of the novel coronavirus. Consequently, in a view of prevention being better than cure, probiotics have become a neutraceutical and promising immunobiotic agents to possibly treat the infection of COVID-19.")

18 (2020 review of probiotics & COVID; "Lactobacilli and bifidobacteria have shown a promising beneficial effect and administration of them can overcome the gut dysbiosis induced by the SARS-CoV2 infection.")

19 (2019 study found that "Preliminary findings on how probiotic treatments, called psychobiotics, may help improve your mood, decrease your anxiety, and strengthen your memory suggest that in the near future these probiotics could be prescribed to treat depression, anxiety, and other mental health issues.")

20 (2017 review of 10 studies found that "The evidence for probiotics alleviating depressive symptoms is compelling.")

21 (causes of leaky gut)

22 (causes of leaky gut)

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