Prebiotics vs probiotics: what are the differences and why do you need both

Probiotic, prebiotic, synbiotic, postbiotic – the terminology of the gut is becoming increasingly complicated, and marketers are eager to use these terms interchangeably. Meanwhile, the difference between a prebiotic and a probiotic is fundamental, and the effectiveness of both largely depends on whether you provide both simultaneously. Why do you need prebiotics just as much as probiotics? Which prebiotics have the best scientific evidence? And when is a probiotic without a prebiotic only half the success?

KEY INFORMATION
• New definition of prebiotics according to Hill et al. (Nature Reviews Gastroenterology and Hepatology, 2014): "substrate selectively fermented by microbiome microorganisms, providing beneficial health effects to the host".
• Butyrate produced by the fermentation of prebiotics by gut bacteria seals the gut barrier and nourishes colonocytes – Canani et al. (Gut Microbes, 2011) showed that butyrate increases the expression of tight junction proteins (claudin, occludin).
• A synbiotic (prebiotic + probiotic together) is more effective than each component alone in insulin resistance and metabolic disorders.
• Prebiotics good for IBS: gradual introduction – a sudden increase in fermentation can exacerbate symptoms before improvement.

Definitions – what do these terms really mean?

Probiotic (WHO/FAO definition 2002): "live microorganisms that, when administered in adequate amounts, confer a health benefit on the host". Key word: "live". A probiotic is a live bacterium or yeast (e.g., Saccharomyces boulardii) – it must survive the passage through the acidic environment of the stomach and reach the large intestine in sufficient quantities (min. 10⁸–10¹⁰ CFU, colony forming units). Examples: Lactobacillus rhamnosus GG, L. acidophilus, Bifidobacterium longum, B. bifidum, Streptococcus thermophilus.

Prebiotyk: „substrat selektywnie fermentowany przez mikroorganizmy mikrobiomu gospodarza, co daje korzystne efekty zdrowotne” – definicja zaktualizowana przez Gibson et al. (Nature Reviews Gastroenterology and Hepatology, 2017). Key point: "selectively" – a prebiotic must preferentially feed beneficial bacteria, not all microorganisms (including pathogens). A prebiotic is indigestible fiber that reaches the large intestine undigested. Examples: inulin, FOS, GOS, resistant starch, pectins, arabinoxylans, lactulose (synthetic prebiotic).

Postbiotic (a new term): metabolites produced by gut microbes as a result of fermentation – butyrate, propionate, acetate (short-chain fatty acids, SCFA), lactic acid, B vitamins. Postbiotics are the result of the action of probiotics and prebiotics, but they can also be supplied directly (e.g., butyrate supplements). Synbiotic: a preparation containing both a probiotic and a prebiotic, selected so that the prebiotic nourishes the specific probiotic strains provided.

Our observations: Probiotics without prebiotics are like planting a garden without fertilizing – probiotic bacteria may not survive long-term in the gut without an adequate supply of substrate. Colonization studies show that Lactobacillus and Bifidobacterium return to baseline levels within 2–4 weeks after stopping a probiotic course if the diet does not provide an adequate amount of fermentable fiber. Long-term changes in the microbiome require dietary changes, and a supplement is only an addition.

Main types of prebiotics – how do they differ?

Inulin and FOS (fructooligosaccharides): the most popular and well-researched prebiotics. Obtained mainly from chicory root (Cichorium intybus), Jerusalem artichoke, onions, and garlic. Selectively stimulate Bifidobacterium and Lactobacillus. Dosage: 5–15 g per day. At doses above 15 g: bloating, gas, diarrhea in sensitive individuals – a typical effect of intense fermentation. FOS has a lower degree of polymerization than long-chain inulin (lcFOS), which means faster fermentation mainly in the small intestine, while long-chain inulin ferments deeper in the colon. A combination of short- and long-chain prebiotics (Synergy1 – scientific brand, not a product) provides better coverage of the entire gut.

GOS (galactooligosaccharides): enzymatically produced from lactose (using the enzyme beta-galactosidase – the end product contains no free lactose, making it safe for lactose-intolerant individuals). Selectively support Bifidobacterium, particularly B. longum and B. breve. Particularly important in pediatrics: GOS is added to infant formula as an analog of human milk oligosaccharides (HMO), which naturally shape the infant microbiome and prevent allergies. Dosage for adults: 4–8 g per day, well tolerated even by individuals with sensitive guts, as the fermentation profile is milder than that of FOS.

Resistant starch (RS): a fraction of starch that is not digested by intestinal enzymes and reaches the colon as a prebiotic. Types: RS1 (physically inaccessible – starch in whole grains), RS2 (raw starch with a specific structure – green bananas, raw potatoes), RS3 (retrograded – formed during cooling of cooked starch: cold rice, potatoes the day after cooking). Bindels et al. (Nature Reviews Microbiology, 2015) demonstrated that resistant starch preferentially nourishes Ruminococcus bromii, Faecalibacterium prausnitzii, and Akkermansia muciniphila – strains associated with metabolic health and reduced inflammation.

The gut-brain axis – why does the microbiome affect mood?

The gut produces about 90% of serotonin in the body (through enterochromaffin cells under the influence of butyrate from SCFA) and is connected to the brain via the vagus nerve. This bidirectional communication pathway – the gut-brain axis – is actively regulated by the composition of the microbiome and may explain why dietary changes (especially an increase in the intake of fermentable fiber) often correlate with improvements in mood and reductions in anxiety. Cryan and Dinan (Nature Reviews Neuroscience, 2012) described the mechanisms by which gut bacteria modulate mood, stress, and behavior: production of neurotransmitters (GABA, serotonin, dopamine by bacteria), influence on the HPA axis (stress), production of SCFA regulating brain gene expression through epigenetics.

Clinical studies show that probiotics reduce symptoms of depression and anxiety: a meta-analysis by Ng et al. (Journal of Affective Disorders, 2018) evaluated 34 RCTs and showed a statistically significant reduction in symptoms of depression (SMD -0.34) and anxiety (-0.36) after probiotics vs placebo. Strains particularly effective: Lactobacillus helveticus R0052 and Bifidobacterium longum R0175 – a combination used in the study by Messaoudi et al. (British Journal of Nutrition, 2011), where it lowered cortisol levels in urine and scores on the Spielberger Anxiety Scale. Prebiotics may act synergistically: a diet rich in fermentable fiber (FOS, inulin) in the study by Schmidt et al. (Psychopharmacology, 2015) reduced cortisol secretion by 32% and improved attention in processing negative information compared to the placebo control group – an effect attributed to increased production of SCFA and modulation of the HPA axis. gut-brain axis

When and how to use probiotics and prebiotics – a practical guide

Probiotics: during antibiotic therapy, take probiotics 2–3 hours after each dose of antibiotics (not together – antibiotics will kill probiotic bacteria). Continue for at least 4 weeks after finishing antibiotic therapy. The strains with the best documentation for antibiotic-associated diarrhea: Lactobacillus rhamnosus GG (LGG) and Saccharomyces boulardii. For IBS (irritable bowel syndrome): Bifidobacterium infantis 35624 and L. rhamnosus GG have the most support in studies. For celiac disease and inflammatory bowel diseases (IBD): only under the supervision of a gastroenterologist – probiotics in Crohn's disease have ambiguous evidence.

Prebiotics in the diet (the best way): 2–3 servings of fiber-rich vegetables and fruits daily: leeks, garlic, onions, Jerusalem artichokes, cooked and cooled potatoes (RS3), green bananas, oats, apples, beans, and lentils. Target fiber intake: 25–35 g per day (the average Polish intake is about 15–18 g, below recommendations). Variety of prebiotics (not just one type) is key to a rich microbiome – each type of fermentable fiber nourishes different strains. Inulin or FOS supplementation: start with 3–5 g daily and gradually increase to 10–15 g over 2–3 weeks to avoid bloating and gas from rapid fermentation. probiotics after antibiotics

Butyrate – why is it the most important product of prebiotic fermentation?

Butyrate (butyric acid, butyrate) is a short-chain fatty acid primarily produced by Roseburia intestinalis, Faecalibacterium prausnitzii, Eubacterium hallii, and other colon bacteria during prebiotic fermentation. It is the main fuel for colonocytes (cells of the colonic epithelium) – providing about 70% of energy for these cells, which is crucial for maintaining the integrity of the gut barrier. Canani et al. (Gut Microbes, 2011) they demonstrated that butyrate stimulates the expression of tight junction proteins (claudin-1, -3, occludin, ZO-1) in enterocytes, which reduces bacterial translocation and "leaky gut".

Beyond the intestines, butyrate has systemic effects: it inhibits HDAC (histone deacetylases) – epigenetic enzymes, which explains its anti-cancer actions in the intestines (proliferation vs differentiation of colonic cells), neuroprotective effects (butyrate modulates microglia and brain inflammation across the blood-brain barrier), and immunomodulatory effects (induction of regulatory T lymphocytes in the intestines that suppress the inflammatory response). To boost butyrate production: a diet rich in resistant starch, inulin, and FOS is most effective. Direct butyrate supplementation (as sodium butyrate or tributyrin acetate) is also available, but costly and has a specific taste and smell.

Synbiotic – when is the combination better than the sum of its parts?

Synbiotics have particular applications in: insulin resistance and metabolic syndrome (the study by Swanson et al., Nature Metabolism, 2020 showed the superiority of synbiotics over probiotics or prebiotics alone in reducing glycemia and lipopolysaccharides – markers of bacterial translocation), remodeling the microbiome after prolonged antibiotic therapy, preparation for pregnancy and during pregnancy (supporting the colonization of the mother’s Bifidobacterium = better colonization of the newborn), traveler's diarrhea, and chronic irregular bowel movements.

How to choose a synbiotic: make sure the prebiotic "matches" the probiotic strain. Bifidobacterium longum + inulin or FOS = a good pair (B. longum is specialized in fermenting inulin due to the enzyme inulinase). L. rhamnosus GG + resistant starch = a good pair (L. rhamnosus ferments starch fractions well). Bifidobacterium lactis + GOS = a good pair (especially for children and seniors, as B. lactis Bb12 is one of the most studied probiotic strains with over 30 RCTs). General supplements "10 strains + inulin" are suitable for general prevention, but specific synbiotics for specific indications (IBS, insulin resistance, antibiotic therapy) have better-proven efficacy based on selected strain-prebiotic pairs. probiotics strain selection

Akkermansia muciniphila – new discoveries and the role of prebiotics

Akkermansia muciniphila is a gut bacterium that has gained significant scientific attention in recent years. It inhabits the mucus layer of the colon and produces short peptides that strengthen the gut barrier. Its low numbers correlate with obesity, insulin resistance, type 2 diabetes, and inflammatory bowel diseases. The study by Plovier et al. (Nature Medicine, 2017) showed that Akkermansia reduces intestinal permeability and improves insulin sensitivity in a mouse model. The first clinical study in humans (Depommier et al., Nature Medicine, 2019) demonstrated safety and improvement of metabolic markers after supplementation of 10¹⁰ CFU A. muciniphila daily for 3 months in overweight patients.

How to naturally increase Akkermansia numbers through prebiotics? Resistant starch (especially RS3 from cold potatoes and cold rice) is the preferred substrate for A. muciniphila. Polyphenols (resveratrol, catechins from green tea, anthocyanins from blackberries and chokeberries) selectively support the growth of A. muciniphila. Diets rich in vegetables, fruits, and prebiotic fibers increase its numbers within a few weeks. This is one of the strongest arguments for a plant-based diet rich in diverse prebiotics – not just FOS and inulin.

Prebiotics and IBS and inflammatory bowel diseases

In irritable bowel syndrome (IBS), prebiotics are a delicate issue: on one hand, they support a beneficial microbiome and the production of SCFAs that seal the gut barrier, on the other hand, FODMAP fermentation (Fermentable Oligosaccharides, Disaccharides, Monosaccharides and Polyols) is one of the mechanisms of pain and discomfort in IBS. The low-FODMAP diet, recommended as the first line for IBS, restricts among others FOS, inulin, and GOS, as their fermentation may exacerbate symptoms in IBS patients.

Paradox: long-term restriction of prebiotics on a FODMAP diet impoverishes the microbiome, which may worsen IBS in the long run. Current recommendations: low-FODMAP diet for 4–6 weeks to assess tolerance, then gradual reintroduction of prebiotics in small portions (starting from 2–3 g of inulin daily) for microbiome rebuilding. Monitoring symptoms allows finding the individual tolerated dose. Working with a dietitian or gastroenterologist for IBS is highly recommended before modifying prebiotic supplementation. An exceptional case in IBS, where prebiotics do not cause problems, is beta-glucan from oats: at a dose of 3–6 g daily, it is well tolerated even in IBS patients due to its specific viscosity, which does not generate as strong fermentation as FOS. It also has proven effects on lowering LDL cholesterol (meta-analysis EFSA 2010), making it a prebiotic with additional metabolic benefits.

In ulcerative colitis (UC) and Crohn's disease, the role of prebiotics is more complex. The bacterium Faecalibacterium prausnitzii, one of the most important butyrate producers, is significantly reduced in IBD patients. Supplementation with inulin and FOS may support the growth of F. prausnitzii and butyrate production, which theoretically supports remission. However, formal gastroenterological guidelines do not yet include prebiotics as a standard treatment for IBD – consultation with a gastroenterologist is essential, as experiments with fermentable fiber during active IBD flare-ups can be risky.

Probiotics and immunity – what do clinical studies say?

Probiotics and immunity is one of the most frequently cited areas, but also one of the most exaggerated by marketing. A reliable picture: a meta-analysis by King et al. (British Journal of Nutrition, 2014) evaluated 20 RCTs and showed that probiotics shorten the duration of upper respiratory infections by an average of 1–2 days and reduce the risk of illness by 12–42% vs placebo, depending on the studied population and strain. Strains with the best immunological evidence: Lactobacillus casei DN-114001 (Actimel), Bifidobacterium lactis BB-12, Lactobacillus rhamnosus GG. The effects are more pronounced in children in nurseries and kindergartens (exposure to infections) and in older adults (immunosenescence).

Prebiotics have an indirect immunological effect through the production of SCFA: butyrate inhibits NF-κB in intestinal immune cells and modulates the pro-inflammatory response, propionate modulates the differentiation of tolerogenic dendritic cells, acetate regulates neutrophil migration. A fiber-rich diet (prebiotics) correlates with a lower incidence of autoimmune and allergic diseases in epidemiological studies – the mechanism of the "old adventure" (hygiene hypothesis): the microbiome shaped by prebiotics regulates the maturation of the immune system.

Frequently Asked Questions

Below are answers to the questions that most often arise about prebiotics and probiotics.

What are prebiotics?

Prebiotics are indigestible food components that selectively nourish beneficial gut bacteria (definition by Gibson et al., 2017). Main prebiotics: inulin, FOS (from chicory, onions, garlic), GOS (from milk), resistant starch (RS3 from cold potatoes and rice), pectins (from apples). Fermented by bacteria into SCFAs (butyrate, propionate, acetate).

What is the difference between prebiotics and probiotics?

A probiotic is a live bacterium that is beneficial for health (WHO/FAO 2002). A prebiotic is an indigestible fiber – food for these bacteria. The probiotic is the gardener, the prebiotic is the fertilizer. Both are essential for lasting improvement of the microbiome. A synbiotic combines both in one preparation for a synergistic effect.

What is a synbiotic?

A synbiotic is a preparation that contains both a probiotic and a prebiotic, selected so that the prebiotic nourishes the administered bacterial strains. For example, Bifidobacterium longum + inulin FOS. The study by Swanson et al. (Nature Metabolism, 2020) showed a better metabolic effect of the synbiotic than each component separately in insulin resistance.

Which prebiotics are the most researched?

Inulin and FOS from chicory (selective stimulation of Bifidobacterium), GOS from milk (important in infancy), resistant starch RS3 (from cold potatoes, supports Akkermansia muciniphila), apple and citrus pectins. Bindels et al. (Nature Reviews Microbiology, 2015) indicated resistant starch as particularly beneficial for Faecalibacterium prausnitzii.

When to take probiotics and prebiotics?

Probiotics in the morning with a meal or 2–3 hours after antibiotics. Prebiotics with meals, gradually increasing the dose from 3–5 g to 10–15 g daily over 2–3 weeks to avoid bloating from intense fermentation. Synbiotic – in the morning with the first meal for optimal colonization and survival of bacteria.

This article is for informational and educational purposes and does not replace consultation with a doctor. If you are pregnant, breastfeeding, taking medications, or have chronic conditions, consult the use of supplements or herbs with a specialist.

Author: Michał Waluk · Published: 2026-05-04 · Updated: 2026-05-04