Prebiotics, probiotics, postbiotics: what are they and why do they matter?

We explain the difference between these gut-friendly terms.

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Author: Dr Joshua Smith - Research Scientist MBBS, BMedSci, PGCertMedEd

Reviewed by: Dr Tina Ghela - Clinical Excellence Lead, MBBS, MRCGP, BSc (Hons)

Updated on: 21 November 2025

Prebiotics, probiotics, and postbiotics help our body to build and maintain a healthy colony of bacteria, which ultimately supports the gut and aids digestion. But, what’s the difference between them all, and how do you get them into your diet? 

Probiotics can be found in fermented foods

What are probiotics?
 

Probiotics are live bacteria and yeasts that provide health benefits [3][6].

In humans, probiotics primarily consist of the following bacterial families: 

  • Lactobacillus
  • Bifidobacterium
  • Streptococcus
  • Enterococcus
  • Lactococcus

But there are many other families, and even yeasts, such as Saccharomyces, are probiotics [2].

What do probiotics do?

Often referred to as “friendly” bacteria, probiotics keep a normal balance of bacteria in your gut.

Probiotics can: 

  • Reduce the frequency and duration of diarrhoea following antibiotics, rotavirus infection, and chemotherapy 
  • Restore natural gut flora 
  • Boost the immune system
  • Prevent the growth of harmful gut bacteria (including reducing counts of Coli and H. Pylori) 
  • Produce B vitamins and enhance absorption of other vitamins and minerals 
  • Reduce total cholesterol, blood sugar levels and C-reactive protein (an inflammatory marker) [2][3][5] 

What food is high in probiotics?

The best way to get probiotics into your diet is by eating probiotic-rich foods. The best probiotic foods are fermented foods that contain live cultures.

This includes [9]:

  • Yoghurts 
  • Kimchi 
  • Sauerkraut 
  • Kombucha 
  • Cheeses 
  • Miso
  • Pickles 
  • Raw unfiltered apple cider vinegar 

Some branded probiotic supplements are readily available in most supermarkets. And can be beneficial in the treatment of specific gastrointestinal disorders. 

Probiotic supplements include [10]: 

  • Activia 
  • Danactive 
  • Culturelle 
  • Align

However, it is worth carrying out some research before trusting marketing claims or at least taking it with a pinch of salt. Some may be biased or unsupported by clinical trials. 

Are probiotics worth it?

Probiotics are a dietary supplement rather than a drug, so clinical testing on the benefits of probiotics isn’t as rigorous as it could be.

The number of bacteria in a probiotic is measured in colony-forming units (CFU). Sometimes, the CFU value is not high enough for it to provide health benefits. This might be due to: 

  • Stomach acid- some bacteria cannot survive acidic conditions 
  • Manufacturing processes- such as high temperatures and pressures when the probiotic is being made 

So, be wary of false marketing claims. With the exception of vitamin D, food is usually better than supplements.

Onion and garlic contain prebiotic fibres

What are prebiotics?
 

While probiotics are living organisms, prebiotics are their food.

Prebiotics are non-digestible carbohydrate nutrients that stimulate the growth or activity of certain microorganisms [5]. Essentially, they’re plant-based fibres that supply good bacteria with what they need to grow.

Prebiotics have been shown to enrich and boost the number of many types of gut bacteria, such as [4,5]: 

  • Bifidobacteria
  • Lactobacilli
  • Ruminococcus
  • rectale
  • Roseburia [4] 

What are the health benefits of prebiotics?

As prebiotics boost probiotics (are you still following?), their health benefits are similar.

Prebiotics may be used as an alternative to probiotics or taken together. Products containing both can have a beneficial additive effect compared to taking a prebiotic or probiotic alone. We call them “synbiotics” as they work together [2]. 

Which are prebiotic foods?

Sources of prebiotics include [5,13]: 

  • Soybeans 
  • Unrefined wheat and barley 
  • Raw oats 
  • Bananas 
  • Garlic 
  • Chicory roots 
  • Leeks 
  • Onions

Prebiotics, unlike probiotics, are not live cultures. Therefore, although cooking and food manufacture may alter their chemical composition, it is of less concern than probiotics [14]. 

What are postbiotics?
 

Postbiotics are fairly new in the field of ‘biotics’ and their exact definition is still under discussion. But in general, it refers to the substances produced by the good bacteria in the gut after they break down prebiotics, which are beneficial to your health. [15].

What are examples of postbiotics?

There’s many different types of postbiotics.

This includes [1]:

These are an example of postbiotics and can be administered directly for potential health benefits. They present an exciting opportunity moving forward in the world of gastrointestinal and overall health. 

Should I take probiotic or prebiotic supplements?

Should I take prebiotic or probiotic supplements?
 

Prebiotics, probiotics, and postbiotics can have significant proven health benefits. Yet, as is the case in the supplement industry, there are many products on the market making claims with little or no clinical evidence.

Whether they work at their best will depend on many factors, including: 

  • The quantity and type of microbial strain 
  • The quality of the product 
  • How it is stored (which can vary considerably) 

In general, biotic supplements are safe for most individuals to take.

However, there are a few exceptions, including: 

  • People who are immunocompromised 
  • People with short gut syndrome
  • Elderly people [16] 

People in the above list should proceed with caution and speak to a healthcare professional before taking any prebiotic or probiotic supplements. 

As with many supplements, their perceived benefits differ between individuals, and something that suits one person may not be right for you. Sometimes trialling products is the best way forward. Helpfully, the World Gastroenterology Organisation has provided an evidence-based list of probiotics that may be beneficial for certain conditions.

Can prebiotics, probiotics, and postbiotics support a healthy gut?
 

Our gut flora plays a vital role in our overall health. One of the ways we can maintain a healthy gut is through consuming prebiotic- and probiotic-rich foods. Supplements are another good source, but it is worth reading the label and any surrounding literature to be sure its claims are valid. 

If you’d like to find out more about how your diet is influencing your health, we've a range of Nutrition Blood Tests to choose from, to help you know whether your body is getting the vitamins it needs. 

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References 

  1. Khan, R., Petersen, F. C., & Shekhar, S. (2019). Commensal Bacteria: An Emerging Player in Defense Against Respiratory Pathogens. Frontiers in immunology, 10, 1203. https://doi.org/10.3389/fimmu.2019.01203 
  2. Markowiak, P., & Śliżewska, K. (2017). Effects of Probiotics, Prebiotics, and Synbiotics on Human Health. Nutrients, 9(9), 1021. https://doi.org/10.3390/nu9091021 
  3. Valdes, A., Walter, J., Segal, E. and Spector, T. (2018). Role of the gut microbiota in nutrition and health. BMJ, 361:k2179 doi:10.1136/bmj.k2179 
  4. Thursby, E., & Juge, N. (2017). Introduction to the human gut microbiota. The Biochemical journal, 474(11), 1823–1836. https://doi.org/10.1042/BCJ20160510 
  5. Singh, R.K., Chang, HW., Yan, D. et al. (2017). Influence of diet on the gut microbiome and implications for human health. J Transl Med 15, 73. https://doi.org/10.1186/s12967-017-1175-y 
  6. Reid G, Gadir AA, Dhir R. Probiotics: Reiterating What They Are and What They Are Not. Front Microbiol. 2019 Mar 12;10:424. doi: 10.3389/fmicb.2019.00424. PMID: 30930863; PMCID: PMC6425910. 
  7. NHS.(2021) Probiotics. [online] [Accessed 30 October 2025].
  8. Marco, M.L., Sanders, M.E., Gänzle, M. et al. (2021) The International Scientific Association for Probiotics and Prebiotics (ISAPP) consensus statement on fermented foods. Nat Rev Gastroenterol Hepatol 18, 196–208. https://doi.org/10.1038/s41575-020-00390-5 
  9. National Institutes of Health. (2020) Office of Dietary Supplements - Probiotics. [online] [Accessed 30 October 2025].
  10. Ciorba M. A. (2012) A gastroenterologist's guide to probiotics. Clinical gastroenterology and hepatology : the official clinical practice journal of the American Gastroenterological Association, 10(9), 960–968. https://doi.org/10.1016/j.cgh.2012.03.024 
  11. Pandey, K., Naik, S. and Vakil, B. (2015) Probiotics, prebiotics and synbiotics- a review. Journal of Food Science and Technology, 52(12), pp.7577-7587. 
  12. Carlson JL, Erickson JM, Lloyd BB, Slavin JL. (2018) Health Effects and Sources of Prebiotic Dietary Fiber. Curr Dev Nutr. 2018 Jan 29;2(3):nzy005. doi: 10.1093/cdn/nzy005. PMID: 30019028; PMCID: PMC6041804. 
  13. Lomax, A. and Calder, P. (2008) Prebiotics, immune function, infection and inflammation: a review of the evidence. British Journal of Nutrition, 101(5), pp.633-658. 
  14. Gatlin, D., 2015. Prebiotics. Dietary Nutrients, Additives, and Fish Health, pp.271-281. 
  15. Żółkiewicz, J., Marzec, A., Ruszczyński, M. and Feleszko, W., 2020. Postbiotics—A Step Beyond Pre- and Probiotics. Nutrients, 12(8), p.2189. 
  16. Shahrokhi M, Nagalli S. Probiotics. In: StatPearls. StatPearls Publishing, Treasure Island (FL); 2020. PMID: 31985927.