Prebiotics vs probiotics - what's the difference?
Can prebiotics and probiotics help improve gut health?
Prebiotics and probiotics help the body to build and maintain a healthy colony of bacteria, which ultimately supports the gut and aids digestion. But, what is the difference between prebiotics and probiotics and how do you get these bacteria into your diet?
Bacteria and gut health
Bacteria often get a bad name. We may associate them with infection or disease, but this is not always true. Did you know they are vital to the health of your gut?
Prebiotics and probiotics can both strengthen and diversify the bacteria in our bodies. That’s right, bacteria in our bodies are actually beneficial.
How can bacteria help us? [1,2]:
- Producing various nutrients
- Protecting the body from ‘bad’ bacteria
- Regulating a normal immune response
About 100 trillion microorganisms line our gastrointestinal tracts- also known as the gut flora or microbiota.
This mini ecosystem is primarily comprised of bacteria and supports the growth of other specialist microbes. These specialist microbes release short-chain fatty acids (SCFAs) - a group of substances that have many functions in the body .
SCFAs are responsible for:
- Regulating fats and blood sugar levels
- Acting as an energy source for gut cells
- Contributing to the healthy gut lining
- Modulating appetite
- Regulating the immune system
SCFAs are also known to have anti-cancer and anti-inflammatory properties .
Unsurprisingly, an imbalance of these gut flora can directly impact our health. And people with certain gut conditions are likely to have a reduced mix of bacteria (also known as reduced bacterial biodiversity), which indicates a link between gut biodiversity and general health.
Conditions where bacterial biodiversity is likely to be reduced include :
- Coeliac disease
- Inflammatory bowel disease
- Atopic eczema
- Arterial stiffness
Fortunately, something as simple as changing your diet can have quite an immediate effect (within 24 hours) on the makeup of bacteria in the gut .
What's the difference between prebiotics and probiotics?
Probiotics are the creators, they’re the ones that are increasing the number of good bacteria in the body. They’re trying to build back the good bacteria after you lose some (through things like taking antibiotics). If you think of your gut ecosystem as a business, the probiotics would be HR, constantly recruiting and looking after employees.
Prebiotics, however, are the suppliers. They supply the good bacteria with what it needs to grow. Using the same analogy, these could be the wholesalers that a business uses to provide office space and computers.
Scientifically speaking, probiotics are live bacteria and yeasts that provide some health benefits . They can be added to yoghurts or taken as food supplements and must meet the safety and functional criteria provided by food safety authorities .
Human probiotics primarily consist of the following bacterial families:
Though, there are many others and even yeasts such as Saccharomyces  are probiotics.
- 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 E. 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) 
Do probiotics work?
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.
How to get probiotics into your diet
Fermented foods that contain live cultures and could sometimes constitutea probiotic include :
- 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 :
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.
Prebiotics are non-digestible carbohydrate components that stimulate the growth or activity of certain microorganisms . Essentially, they are nutrients that allow the “good bacteria” in our gut to thrive.
Prebiotics have been shown to enrich and boost the number of many types of gut bacteria, such as [4,5]:
- E. rectale
- Roseburia 
Some of the possible health benefits of prebiotics include:
- Increasing numbers of Bifidobacteria and Lactobacilli in the gut
- Reducing duration of diarrhoea
- Enhancing absorption of certain minerals such as calcium
- Reducing the risk of cardiovascular disease
- Decreasing harmful bacteria populations
- Improving immunity 
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 .
Sources of prebiotics
Sources of prebiotics include [5,13]:
- Unrefined wheat and barley
- Raw oats
- Chicory roots
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 .
What about postbiotics?
Postbiotics are fairly new in the field of ‘biotics’ and their definition is still under discussion. They are effectively the end-product of gut flora metabolism and can include small microbial fragments, metabolites, and other small compounds .
Remember the short-chain fatty acids we discussed earlier? 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 prebiotic or probiotic supplements?
Prebiotics and probiotics can have significant proven health benefits. Yet, 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, prebiotics and probiotic 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 
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 and probiotics 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, our home Nutrition Blood Test can tell you whether your body is getting the vitamins and minerals it needs.
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- 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
- Thursby, E., & Juge, N. (2017). Introduction to the human gut microbiota. The Biochemical journal, 474(11), 1823–1836. https://doi.org/10.1042/BCJ20160510
- 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
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- National Institutes of Health. (2020) Office of Dietary Supplements - Probiotics. [online] Ods.od.nih.gov. Available at: <https://ods.od.nih.gov/factsheets/Probiotics-HealthProfessional/#en3> [Accessed 27 September 2021].
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