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Prebiotics vs. Probiotics: What’s the difference?

Confusing probiotics and prebiotics is a normal occurrence for many, especially amidst the growing gut health conversation. While a one-letter difference makes for an easy slip up, it is important to understand how they work differently to positively impact your overall health.

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IntroductionProbiotics PrebioticsFAQsSummaryAdditional ResourcesCitations

Welcome to Gut Mania, where gut health, probiotics, and the microbiome are currently buzzing in conversation, headlines, and hashtags. A quick search will yield over 1.8 million #probiotics posts on Instagram, a staggering 1.4 billion #guthealth video views on TikTok, and over 33.6 million search results on Google for the difference between pre and probiotics

While probiotics and prebiotics can both have a profound impact on your digestive and overall health, they are not one in the same. Probiotics are live strains of microbes, while prebiotics are non-living compounds, often plant-based. In order to make informed decisions about which prebiotic and/or probiotics are right for you, it’s important to understand the nerdy differences. 

What are probiotics?

The term “probiotic” is often used loosely, applied to anything with the presence of a microbe. But this is only part of the picture, and it’s important that we get it right. 

According to ISAPP— the International Scientific Association for Probiotics and Prebiotics—and the scientific community, “probiotics” are: “Live microorganisms that, when administered in adequate amounts, confer a health benefit on the host.”1 (Fun fact from the Seed-verse: this definition was first authored by a 2002 UN/WHO expert panel, chaired by Seed’s Scientific Board Member, Dr. Gregor Reid.) Find a full breakdown of this definition here

In simpler terms, probiotics are live microorganisms (often bacteria) that have been studied in specific amounts to carry out specific actions for the host.

What do probiotics do? 

Probiotic organisms can provide a variety of benefits within the body, depending on the specific strain at hand and its clinically studied dosage. Some probiotic strains can synthesize vitamins.2 Others can produce neurotransmitters.3 There are also strains that enhance gut-barrier function,4 assist in the breakdown of foods,5 and prevent pathogens from invading the gut barrier.6 (Explore what probiotics can do for non-humans, too.)


How do probiotics work?

Most probiotic strains are transient microbes, meaning they travel through your digestive tract,  as opposed to taking up residence (aka colonizing or proliferating). Along the way, they interact with your immune cells, host cells, dietary nutrients, and resident microbes to directly and indirectly deliver their benefits before exiting your system.

Generally, probiotics work in the following ways:

  1. They regulate the composition and activity of your resident microbes by inhibiting potential pathogens, and also by stimulating the growth of beneficial microbes as extra defense against pathogens.
  2. They inhibit the passage of harmful pathogens or inflammatory compounds across the gut barrier.
  3. They fine-tune local and systemic immune responses by interacting with immune receptors and modulating immune pathways and cells.
  4. They regulate systemic metabolic functions. For example, they can produce vitamins, amino acids, or enzymes which can have beneficial impacts on biomarkers like cholesterol levels.
  5. They modulate neurologic functions via the gut-brain axis. They can do this by producing neurotransmitters that travel through the bloodstream to the brain.

A probiotic does not need to exert all of these functions to be a probiotic—though probiotics often do have multiple modes of action.

What are prebiotics? 

Prebiotics are often described as the food that feeds our microbes, though this is just part of the story. Let’s begin by reviewing the scientific definition: ISAPP defines a prebiotic as “a substrate that is selectively utilized by host microorganisms conferring a health benefit.”7

What does this mean? In order for something to be considered prebiotic under this definition, it must meet certain criteria. First, it must be used by a targeted group of microbes, as opposed to broadly affecting the microbiome as a whole. Second, scientific research must show that it is used by beneficial microbes, whose benefit (at least partially) relies on usage of the prebiotic.

In other words, to be a prebiotic, it must help specific microbes carry out a specific beneficial function in your body.


How do prebiotics work? 

Under the ISAPP definition, there are several types of prebiotics and mechanisms by which they function.

  • Prebiotics that “feed” gut microbes and encourage growth are typically non-digestible carbohydrates and can come in a variety of forms. This class of prebiotics can’t be broken down by our own bodies and are instead fermented by resident microbes, producing useful8 short-chain fatty acids (SCFAs), including butyric acid (butyrate) and propionic acid (propionate). SCFAs play a core role in our health, including brain health via the gut-brain axis and the regulation of metabolic, endocrine, and immune functions.
  • Another type of prebiotic includes compounds that can be biotransformed (or chemically modified) by gut bacteria into beneficial metabolites. So, prebiotics aren’t just a source of food for your microbes. Certain prebiotics can actually be converted by microbes into new substances that benefit health.These plant-based prebiotics (which include punicalagins) are the type of prebiotic compounds included in our DS-01™ Daily Synbiotic. Punicalagins are a type of polyphenol found in pomegranates, which have been shown to have three times the antioxidant activity of red wine and green tea.9 Certain gut bacteria metabolize punicalagins into urolithin A, a powerful molecule that manages the recycling of defective mitochondria. As the powerhouse of the cell, mitochondria are responsible for producing energy, and maintaining healthy mitochondrial function is important for optimal metabolism and energy production. The prebiotic in our PDS-08™ Pediatric Daily Synbiotic is a 50/50 blend of fructooligosaccharides (FOS) and inulin. Both inulin and FOS are soluble dietary fibers and have prebiotic action in the body.

While prebiotics are mostly various types of carbohydrates, they aren’t exclusively carbohydrates. Other words to describe prebiotics that you’ll see on labels, backs of supplements, and food ingredient lists are fructans, like inulin and fructo-oligosaccharides (FOS), as well as galacto-oligosaccharides (GOS), xylo-oligosaccharides (XOS) resistant starch, pectic oligosaccharides, and cocoa-derived flavanols. 

Prebiotics and probiotics are really important not only for your gut health, but the health of your body as a whole.

Can you get probiotics and prebiotics from food? 

The short answer is yes, but dietary inputs are not always a reliable source of probiotics or prebiotics. Let’s take a deeper look at each.

We’ll start with probiotics. You may have noticed that the terms “fermented foods” and “probiotics” seem to be used interchangeably. Fermented foods and beverages, like kimchi and kombucha, are sometimes characterized or labeled as “probiotic foods” or “contains probiotics”. These declarations, although well-intended, should only be used when there is a demonstrated health benefit in humans conferred by well-defined and characterized live microorganisms. 

This is not to say that you shouldn’t eat or drink fermented foods and beverages. Many are extremely nutritious, very tasty additions to your daily diet, and they may contain beneficial bacteria and metabolites. However, they are not necessarily reliable sources of a probiotic intended for a specific benefit. For example, if you consume a fermented food or beverage, it may have bacteria, but do you know which strains? In what amounts? Have they survived digestion and landed in your colon? Have those strains been studied, in those amounts, to do something in the human body? That said, efforts are being made by the scientific community to more clearly define fermented foods and clarify what is considered a probiotic food, and what is not.10

If you want to get verifiable probiotics, you’ll most likely need to get them through supplementation. To note: there is also a lot of variability in the probiotics available, and there are some important questions you should ask before deciding which probiotic is right for you. 

When it comes to prebiotics, you may be used to seeing terms and phrases like “prebiotic foods” or “foods high in prebiotics”. Prebiotics are commonly associated with dietary inputs, and it is possible to consume prebiotics from foods naturally rich in prebiotic substances (including garlic, onion, honey, asparagus, apples, certain grains like barley and rye, and more). It’s important to note, though, that the concentration of prebiotics in dietary sources is variable. 

Can you take probiotics and prebiotics together?

Yes, prebiotics and probiotics can be taken together. Because prebiotics and probiotics carry out different functions within your body, taking them together is a great way to maximize the benefits for your gastrointestinal and systemic health. 

The term “synbiotic” refers to the combination of both probiotics and prebiotics (hence the names for our DS-01™ Daily Synbiotic and PDS-08™ Pediatric Daily Synbiotic). Synbiotics may work synergistically, meaning the prebiotic in a formulation is used by the microbes in that formulation. Or they can be complementary, meaning the prebiotic is utilized by the microbes that already reside in your gut. Lastly, ingestion of either type of synbiotic has been demonstrated to impart a health benefit.11

So, what is the difference between probiotics and prebiotics?

Though the names are quite similar, there are important differences between pre and probiotics, and how they function in the body. Prebiotics are not microorganisms, but are non-living compounds that are used by microbes in some way that is beneficial to the host, or human body. These are often plant compounds such as certain fibers or polyphenols, though they can also be compounds like polyunsaturated fatty acids or even human milk oligosaccharides (HMOs) found in breast milk. Probiotics, on the other hand, are live microorganisms that provide a health benefit, such as supporting digestion in the body.

TL;DR: Prebiotics and probiotics not only support your gut health, but also the health of your body as a whole. As we’ve explored, in order to impart the benefits that prebiotics and probiotics have to offer, it is important to ensure you’re consuming them from reliable sources (usually, through supplementation). 

If you read this far, we hope you are feeling confident and empowered to make informed decisions about the prebiotics and/or probiotics you choose to consume. 

Helpful articles and resources about probiotics:

Probiotics: Reiterating What They Are and What They Are Not: This is a review article co-authored by one of our Scientific Board Members, Dr. Gregor Reid, and published in the scientific journal Frontiers in Microbiology. It articulates the scientific definition of probiotics and explains why it’s so important that we use it appropriately.

Clinical Guide to Probiotic Products Available in USA: This is an up-to-date reference on probiotics available in the U.S. and their benefits, published by the Alliance for Education on Probiotics. Use this guide to help you find the right probiotic for adult health, women’s health, and pediatric health. 

Probiotics: What You Need to Know: This helpful guide from the National Center for Complementary and Integrative Health at the National Institutes of Health (NIH) covers a lot of the same ground we covered here, but offers the unique perspective of our government’s scientists and researchers.

Prebiotics: Definition, Types, Sources, Mechanisms, and Clinical Applications: Like to read scientific literature for yourself and want to learn more about prebiotics? This review paper from the open-access journal, Foods, gives a thorough explanation of the different types of prebiotics and covers what scientific research says about the connection between prebiotics and a variety of health conditions.

  1. Hill, C., Guarner, F., Reid, G. et al. The International Scientific Association for Probiotics and Prebiotics consensus statement on the scope and appropriate use of the term probiotic. Nature Reviews Gastroenterology & Hepatology 11, 506–514 (2014).
  2. Markowiak, P., & Śliżewska, K. (2017). Effects of Probiotics, Prebiotics, and Synbiotics on Human Health. Nutrients, 9(9), 1021.
  3. Sarkar, A., Lehto, S. M., Harty, S., Dinan, T. G., Cryan, J. F., & Burnet, P. (2016). Psychobiotics and the Manipulation of Bacteria-Gut-Brain Signals. Trends in neurosciences, 39(11), 763–781.
  4. Rao, R. K., & Samak, G. (2013). Protection and Restitution of Gut Barrier by Probiotics: Nutritional and Clinical Implications. Current nutrition and food science, 9(2), 99–107.
  5. Jäger, R., Purpura, M., Farmer, S., Cash, H. A., & Keller, D. (2018). Probiotic Bacillus coagulans GBI-30, 6086 Improves Protein Absorption and Utilization. Probiotics and antimicrobial proteins, 10(4), 611–615.
  6. La Fata, G., Weber, P., & Mohajeri, M. H. (2018). Probiotics and the Gut Immune System: Indirect Regulation. Probiotics and antimicrobial proteins, 10(1), 11–21.
  7. Gibson, G.R., Hutkins, R, Sanders, M.E., Prescott, S.L., Reimer, R.A., Salminen, S.J., Scott, K., Stanton, C., Swanson, K.S., Cani, P.D., Verbeke, K., & Reid G. Expert consensus document: The International Scientific Association for Probiotics and Prebiotics (ISAPP) consensus statement on the definition and scope of prebiotics. Nature Reviews Gastroenterology & Hepatology, 14(8):491-502. doi:10.1038/nrgastro.2017.75
  8. Davani-Davari, D., Negahdaripour, M., Karimzadeh, I., Seifan, M., Mohkam, M., Masoumi, S. J., Berenjian, A., & Ghasemi, Y. (2019). Prebiotics: Definition, Types, Sources, Mechanisms, and Clinical Applications. Foods (Basel, Switzerland), 8(3), 92.
  9. Gil MI, Tomás-Barberán FA, Hess-Pierce B, Holcroft DM, Kader AA. Antioxidant activity of pomegranate juice and its relationship with phenolic composition and processing. J Agric Food Chem. 2000 Oct;48(10):4581-9. doi: 10.1021/jf000404a. PMID: 11052704.
  10. Marco, M. L., Sanders, M. E., Gänzle, M., Arrieta, M. C., Cotter, P. D., De Vuyst, L., Hill, C., Holzapfel, W., Lebeer, S., Merenstein, D., Reid, G., Wolfe, B. E., & Hutkins, R. (2021). The International Scientific Association for Probiotics and Prebiotics (ISAPP) consensus statement on fermented foods. Nature reviews. Gastroenterology & hepatology, 18(3), 196–208.
  11. Swanson, K. S., Gibson, G. R., Hutkins, R., Reimer, R. A., Reid, G., Verbeke, K., Scott, K. P., Holscher, H. D., Azad, M. B., Delzenne, N. M., & Sanders, M. E. (2020). The International Scientific Association for Probiotics and Prebiotics (ISAPP) consensus statement on the definition and scope of synbiotics. Nature reviews. Gastroenterology & hepatology, 17(11), 687–701.