Probiotics are live microorganisms that may confer a benefit when eaten in adequate amounts. Prebiotics are the fibres that feed the beneficial bacteria already living in your gut [1][2]. Probiotics vs prebiotics, in short, comes down to bacteria versus bacteria food, and it's why some products combine both.
July 24, 2026
Probiotics vs Prebiotics: What You Need to Know
What exactly is a probiotic?
The internationally accepted definition, set out by the International Scientific Association for Probiotics and Prebiotics (ISAPP), describes probiotics as live microorganisms that confer a health benefit on the host when administered in adequate amounts [1]. This means not every fermented food automatically counts. Strain identity, dose and evidence of a specific benefit all matter under this definition.
Common probiotic food sources include live yoghurt, kefir, sauerkraut, kimchi and some aged cheeses. Research suggests certain probiotic strains may be associated with easing specific digestive symptoms, though effects appear to be strain-specific rather than universal across all "good bacteria" [1][3].
What exactly is a prebiotic, and how is it different?
Prebiotics are defined by ISAPP as substrates that are selectively utilised by host microorganisms conferring a health benefit [2]. In practice, this usually means specific types of fibre, such as inulin, fructooligosaccharides (FOS) and galactooligosaccharides (GOS), which resist digestion in the small intestine and are fermented by bacteria in the colon.
Food sources rich in prebiotic fibres include garlic, onions, leeks, asparagus, bananas (particularly slightly under-ripe ones), oats and chicory root. Unlike probiotics, prebiotics do not introduce new bacteria. Instead, they appear to selectively feed and encourage the growth of strains associated with health that are already present in the gut [2].
Do you need both, and can you get them from food alone?
Research suggests probiotics and prebiotics may complement one another, since prebiotics can help support the survival and activity of probiotic bacteria once they reach the gut [2][4]. Many whole foods naturally provide both, or complement each other well in a varied diet, for example live yoghurt (probiotic) paired with oats and banana (prebiotic).
Most people can get meaningful amounts of both from a varied, plant-forward diet. Supplements may help in specific circumstances, such as after a course of antibiotics, but evidence for supplement use varies considerably by strain and formulation, and is not universally established for general gut wellness [1][3].
Probiotics vs prebiotics: a side-by-side comparison
| Probiotics | Prebiotics | |
|---|---|---|
| What they are | Live beneficial microorganisms | Non-digestible fibres and compounds |
| How they work | Introduce or top up beneficial bacteria | Feed bacteria already in the gut |
| Common sources | Yoghurt, kefir, kimchi, sauerkraut | Garlic, onion, banana, oats, chicory |
| Defined by | ISAPP, 2014 consensus statement [1] | ISAPP, 2017 consensus statement [2] |
Frequently asked questions
Can you take probiotics and prebiotics together?
Yes. Products or diets combining both are sometimes referred to as synbiotics. Research suggests the prebiotic component may help support the probiotic bacteria once they reach the gut, though the specific combination and strain matter for any observed effect [2][4].
Are fermented foods the same as probiotics?
Not always. Fermentation does not guarantee live, beneficial bacteria survive in meaningful amounts, particularly in pasteurised or heat-treated products. Look for labels stating "live cultures" if the goal is a probiotic effect [1].
Do probiotic supplements need to be refrigerated?
Some do, depending on the strain and formulation, since certain live bacteria are sensitive to heat and moisture. Always follow the storage instructions on the specific product, as requirements vary between brands and strains [1].
Practical takeaway
If you are building a gut-friendly diet, aim to include both types rather than choosing one over the other. Add a daily source of live-culture probiotic food such as yoghurt or kefir, and pair it with prebiotic fibres like oats, banana, garlic or onion. Introduce new fermented foods gradually, since a sudden increase can cause temporary bloating, and prioritise variety over relying on a single "superfood" or supplement.
Related reading: What Is a Healthy Gut Microbiome? | Everyone's Eating Fermented Food Now | What Is Fibermaxxing? | The 7 Gut Health Metrics Worth Tracking
References
- Hill, C., et al. (2014). Expert consensus document: 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.
- Gibson, G.R., et al. (2017). 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, 491-502.
- NHS. Probiotics. nhs.uk. Note: NHS guidance highlights that evidence for probiotic supplements varies by strain and condition.
- Swanson, K.S., et al. (2020). The International Scientific Association for Probiotics and Prebiotics (ISAPP) consensus statement on the definition and scope of synbiotics. Nature Reviews Gastroenterology & Hepatology, 17, 687-701.
This content is for informational purposes only and does not constitute medical advice. If you have concerns about your digestive health, please speak to a healthcare professional.
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