Getting Real About Gut Health: What Are Probiotics?

Mar 16, 2023 Digestion 5 MIN

Getting Real About Gut Health: What Are Probiotics?

Answering the question “what are probiotics?” starts with getting to know your gut. Whether you know it or not, your gut is already host to a massive, complex community of bacteria.1 And not all bacteria is bad! Many good bacteria actually help the body function.1 There are 38 trillion microbes in your body, the majority of which are in your gut where they play a key role in your health and wellness—and here probiotics can help too.2†

What are probiotics?

Probiotics are microorganisms that provide a health benefit when consumed in certain amounts.2† They can be found in some fermented foods if they contain live microbes. They can also be in other probiotic-containing foods and dietary supplements.2

What are the benefits of probiotics?

You may be wondering how are probiotics good for you? Well, probiotics support overall digestive health.3 They help support a healthy gut microflora which in turn, supports many functions in the body.3†

After we consume probiotics, they can grow, metabolize and interact with other microbes in our guts that influence multiple processes in our body. Once they do their business, most probiotics don’t hang around for too long. That’s why it’s important to consume them on a regular basis. But how do probiotics help, and which exact health benefits they offer depends not only on the type of probiotic but also on the quantity of them.† 

What are the main types of probiotics?

There are literally hundreds of types of probiotics, but the most common come from foods with a long history of safety or are well-known microorganisms in a healthy gut. The most common species come from Lactobacillus (acidophilus, casei, fermentum, gasseri, johnsonii, paracasei, plantarum, rhamnosus, and salivarius) and Bifidobacterium (adolescentis, animalis, bifidum, breve, and longum).4 These are well-known probiotics that are considered beneficial and safe.  

Before you tune out from reading long names like that, if you take away anything from this blog it’s that you don’t have to memorize hundreds of different species and all their unique properties. Lactobacillus and Bifidobacterium are the two main categories of probiotics and they both offer great benefits.  

How to get probiotics from food

Probiotics can be found in fermented foods that contain live microbes. Yogurt is probably the most commonly known food source of probiotics.5 Manufacturers add live microorganisms to milk during the fermentation process to make yogurt.5 Other fermented foods that contain probiotics include most cheeses, kimchi, kombucha, miso, and sauerkraut.6 Probiotics can also be found in dietary supplements, where you can choose strains and dosages. 

How long should I take probiotics? 

There’s no hard data saying probiotics should be taken daily, but most of the studies on probiotics were measured on a daily basis.7 Probiotics don’t stick around in the gut for long, so it stands to reason that continually including multi-strain probiotic supplements in your diet long-term may be beneficial.7 †

Are there any downsides to taking probiotics?

Probiotics have a long history of being considered safe and well-tolerated, especially for generally healthy people.8 Some people may experience some gastrointestinal side effects such as bloating or loose stools at first, but these symptoms seem to fade rather quickly.9 Taking probiotic supplements with food may help reduce side effects but always follow the instructions on your label for best usage.9

What are prebiotics?

We’d be remiss if we didn’t mention prebiotics too! Prebiotics are (mostly) dietary fibers that act like food for the beneficial bacteria in your gut.10 Both probiotics and the good bacteria in your gut use prebiotics to help keep your gut microbiome healthy.11 †

The full scientific definition of a prebiotic is far more nuanced than this, if you’re really interested you can read more about prebiotics here

Where can I find prebiotics?

Most prebiotics are soluble fibers found in a variety of plant-based foods such as onions, lentils, soybeans, garlic, bananas, chicory root, and Jerusalem artichokes (sunchokes). The prebiotics in foods belong to a group of soluble fibers called oligosaccharides, which consist GOS (galactooligosaccharides), and FOS (fructooligosaccharides) such as inulin.  

Prebiotics can also be added to a variety of food products (such as cereals, breads, infant formulas) and dietary supplements. You may not always see the ingredient as “prebiotic” on the label but will see them listed as the food source (e.g. chicory root or chicory fiber) or the name of the individual prebiotic (e.g. inulin, or types of oligosaccharides).

What to look for in a probiotic dietary supplement

1. Genus, Species, and Strain.

Probiotics are categorized into three levels: genus, species, and strain. The two most common genus categories are Lactobacillus and Bifidobacterium. They can be broken down further into species, such as Lactobacillus (genus) acidophilus (species), or Bifidobacterium (genus) lactis (species). 

Some supplements will provide the subtype of species, which is called the strain. For example, Lactobacillus (genus) acidophilus (species) LA-14® (strain) or Bifidobacterium (genus) lactis (species) HN019™ (strain).  

Most species of Lactobacillus and Bifidobacterium offer digestive health benefits, but specific strains are usually trademarked by companies and are targeted for varying health purposes. †  

2. Suggested Dose 

The measurement unit used in most probiotic dietary supplements is Colony Forming Units (CFUs).  These are the number of live or viable microorganisms in one serving. Most probiotic supplements contain 1 to 15 billion CFU per dose, but higher CFU counts don’t always mean a better product. 

The International Scientific Association for Probiotics and Prebiotics recommends at least 1 billion CFU for a general digestive health benefit with doses of 10 to 15 billion CFU for specific purposes.2,12 Always follow directions on the label for the suggested serving size. 

3. Expiration Date

Probiotics are living organisms that die off over a specified time so it’s important to use before the expiration date for full benefit. All probiotic supplements should have an “expiration” or “use-by” date. Avoid probiotic supplements that do not have an expiration date or a have a “time of manufacture” date because there is no certainty it contains viable microorganisms.


We may have so much left to learn about the microcolony inside us all, but one thing is clear—your gut health matters. And probiotics might just be one piece to that puzzle. So if you’re interested, it’s worth a chat with your doctor about which strains might be best for you and where to find them either in food or in dietary supplements. Whatever you decide about probiotics, listen to your body or as one might say—trust your gut (and your doctor). 

† These statements have not been evaluated by the Food and Drug Administration. These products are not intended to diagnose, treat, cure, or prevent any disease.


  1. National Institutes of Health. “5 Things To Know About Probiotics.” 2021. National Center for Complementary and Integrative Health. Accessed on: April 27, 2021.
  2. International Scientific Association for Probiotics and Prebiotics. “Probiotics.” Accessed on: April 27, 2021.
  3. Cresci GA, et al. The Gut Microbiome: What we do and don’t know. Nutr Clin Pract. 2015; 30(6): 734-746.
  4. National Institutes of Health. “Probiotics: Fact Sheet For Health Professionals.” 2020. Office of Dietary Supplements. Accessed on: April 27, 2021.
  5. National Institutes of Health. “Probiotics: Fact Sheet For Consumers.” 2021. Office of Dietary Supplements. Accessed on: April 27, 2021.
  6. International Scientific Association for Probiotics and Prebiotics. “Fermented Foods.” 2020. Accessed on: April 27, 2021.
  7. International Scientific Association for Probiotics and Prebiotics. “FAQs.” 2020. Accessed on: April 27, 2021.
  8. National Institutes of Health. “Probiotics: What You Need To Know.” 2019. National Center for Complementary and Integrative Health. Accessed on: April 27, 2021.
  9. Harvard Medical School. “Should you take probiotics.” 2019. Harvard Health Publishing. Accessed on: April 27, 2021.
  10. International Scientific Association for Probiotics and Prebiotics. “Prebiotics.” Accessed on: April 27, 2021.
  11. International Scientific Association for Probiotics and Prebiotics. “Effects of Probiotics And Prebiotics On Our Microbiota.” 2017. Accessed on: April 27, 2021.
  12. Hill C, et al. Expert consensus document. The International Scientific Association for Probiotics and Prebiotics consensus statement on the scope and appropriate use of the term probiotic. Nat Rev Gastroenterol Hepatol. 2014; 11(8): 506-14.


Carroll Reider, MS

Scientist, Principal Science & Technology

Carroll is a nutrition scientist and communicator with over 25 years of experience as a clinician, researcher, and educator at major universities, medical centers, and nutrition industry settings. She is a passionate advocate of nutritional health and established the nutrition education and science platforms at Pharmavite. Carroll is an expert in personalized nutrition and has published several scientific papers on vitamin and mineral inadequacies and the impact on health and wellbeing. Prior to joining Pharmavite, Carroll taught nutrition at UCLA Medical School and Santa Monica College and was a chief clinical dietitian and researcher.

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