Prebiotics, Probiotics and Postbiotics: What's the Difference?
Gut health has become one of the most popular topics in wellness, and with it a confusing vocabulary: prebiotics, probiotics, synbiotics, postbiotics. These terms sound similar but mean different things. Understanding them helps you make smarter food and supplement choices, and see past marketing hype.
First, the Microbiome
Your gut, mainly the large intestine, is home to trillions of microorganisms, including hundreds of bacterial species. Together they are called the gut microbiome. These microbes help digest fibre, produce certain vitamins such as vitamin K and some B vitamins, train the immune system, and produce compounds that affect the gut lining and beyond. Diversity is generally considered a sign of a healthy microbiome. Our original article A Wakeup Call for Our Dying Microbiome discusses why modern lifestyles may be reducing that diversity.
Prebiotics: Food for Your Microbes
The International Scientific Association for Probiotics and Prebiotics (ISAPP) defines a prebiotic as "a substrate that is selectively utilised by host microorganisms conferring a health benefit." In plain terms: prebiotics are mostly special fibres that feed beneficial bacteria.
Common prebiotics
- Inulin and fructooligosaccharides (FOS): in chicory root, onions, garlic, leeks, asparagus, Jerusalem artichoke
- Galactooligosaccharides (GOS): in beans, lentils, chickpeas
- Resistant starch: in slightly green bananas, oats, and cooked-then-cooled potatoes, rice and pasta
- Beta-glucans: in oats, barley and mushrooms
- Polyphenols: in berries, cocoa, green tea and olive oil, which also interact with gut microbes
Learn about all fibre types in our complete fibre guide.
Probiotics: Beneficial Live Microbes
Probiotics are defined by ISAPP and the World Health Organization as "live microorganisms that, when administered in adequate amounts, confer a health benefit on the host." Key points:
- Strain matters: benefits are specific to particular strains, such as Lactobacillus rhamnosus GG or Bifidobacterium lactis BB-12. A benefit shown for one strain cannot be assumed for another.
- Dose matters: studies use specific amounts, measured in colony-forming units (CFU).
- Evidence varies: some strains have good evidence for specific situations, such as reducing antibiotic-associated diarrhoea; for many other claims, evidence is limited.
Fermented foods vs. probiotics
Not all fermented foods are probiotics in the strict scientific sense, because their microbes are not always defined or tested for specific benefits. Some fermented foods, such as sourdough bread and most beer, contain no live microbes after baking or filtering. Still, fermented foods like yoghurt, kefir, fresh kimchi, sauerkraut and miso are valuable parts of a varied diet. Explore them in our Korean fermented foods guide.
Synbiotics: Working Together
A synbiotic combines live microorganisms with a substrate they use. Some products pair probiotics with prebiotic fibres. You can create your own "food synbiotic" by eating yoghurt with oats and banana, or kimchi alongside beans and vegetables.
Postbiotics: The Beneficial By-Products
In 2021, ISAPP defined a postbiotic as "a preparation of inanimate microorganisms and/or their components that confers a health benefit on the host." This includes heat-killed microbes and their components. The term is also used more loosely for beneficial compounds microbes produce, such as:
- Short-chain fatty acids (SCFAs): butyrate, acetate and propionate, produced when bacteria ferment fibre. Butyrate is the main fuel for colon cells.
- Vitamins: such as vitamin K2 and some B vitamins; see our vitamin K2 guide.
- Organic acids: such as lactic acid in fermented foods.
Long-fermented traditional products such as Wild Fermented Plant Enzymes contain fermentation by-products of this kind; read more in our plant enzymes guide.
Quick Comparison
| Term | What it is | Food examples |
|---|---|---|
| Prebiotic | Food for beneficial microbes | Onions, garlic, oats, beans, green bananas |
| Probiotic | Defined live microbes with proven benefit | Some yoghurts and kefirs; supplements |
| Fermented food | Food transformed by microbes | Kimchi, sauerkraut, miso, kombucha |
| Synbiotic | Microbes plus their food | Yoghurt with oats and fruit |
| Postbiotic | Inactive microbes or their beneficial products | SCFAs from fibre fermentation |
Practical Steps for a Healthier Microbiome
- Eat 30 different plant foods a week.
- Include a prebiotic-rich food daily, such as onions, garlic, oats or beans.
- Add a fermented food daily, starting small.
- Limit ultra-processed food and artificial sweeteners, which some studies suggest can affect gut bacteria.
- Use antibiotics only when prescribed, and finish the course as directed.
- Sleep well, manage stress and move daily; see our gut-brain axis guide.
Who Should Be Cautious?
People who are severely immunocompromised, critically ill or have had recent major surgery should talk to their doctor before taking probiotic supplements. People with IBS may find some prebiotic fibres increase bloating; see our bloating guide.
Frequently Asked Questions
Should I take a probiotic after antibiotics?
Some specific strains have evidence for reducing antibiotic-associated diarrhoea. Ask your doctor or pharmacist which strain and dose is appropriate.
Are probiotic supplements regulated?
In many countries, including the USA, probiotics are sold as dietary supplements with less oversight than medicines. Choose brands that list strains and CFU counts and use third-party testing.
The Takeaway
Prebiotics feed your microbes, probiotics add specific beneficial ones, and postbiotics are the useful products and components they leave behind. The most reliable approach is a diverse, plant-rich diet with fermented foods, supported by good sleep, movement and stress management.
Related Articles
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- Intermittent Fasting for Beginners: Methods, Evidence and Safety
- Liver Health Awareness: Understanding Fatty Liver and How to Protect Your Liver
- COVID-19: A Wakeup Call for Our Dying Microbiome
Disclaimer: This article is for general educational purposes only. These statements have not been evaluated by the Food and Drug Administration. Live Pine products are not intended to diagnose, treat, cure or prevent any disease. Always consult a qualified healthcare professional before starting a new supplement, especially if you are pregnant, nursing, taking medication or managing a health condition.
