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

Probiotic, prebiotic, postbiotic, synbiotic: four words from the same family tree that marketing uses interchangeably. The difference is simple and can be remembered once. A probiotic is live bacteria. A prebiotic is the food that these bacteria ferment. A postbiotic is the metabolites produced from this fermentation. A synbiotic combines the first two in one preparation. The practical consequence is that a probiotic alone, without a supply of fermentable fiber, rarely changes the microbiome for longer than a few weeks. The capsule adds bacteria, while the diet determines whether they will remain. Therefore, the question is not so much 'which probiotic' but 'what to feed it'. Below you will find definitions from ISAPP consensus documents, an overview of the best-researched prebiotics, guidelines for combining both groups, and a comparison of probiotic preparations available in the u Bucha store along with the cost of one serving.

KEY INFORMATION
• A prebiotic is a substrate selectively used by the host's microorganisms (Gibson et al., Nature Reviews Gastroenterology and Hepatology, 2017), while a probiotic consists of live cultures.
• Butyrate accelerates the assembly of tight junctions in the epithelium through AMPK kinase (Peng et al., The Journal of Nutrition, 2009).
• A meta-analysis of 10 studies found no overall effect of probiotics on mood (Ng et al., 2018).
• Prebiotyk wprowadzaj stopniowo, od 3-5 g do 10-15 g dziennie przez 2-3 tygodnie.

What is the difference between a prebiotic and a probiotic?

A probiotic is live microorganisms that, when administered in the right amount, confer a health benefit to the host. A prebiotic is a substrate selectively used by the host's microorganisms. The first definition was confirmed by the ISAPP panel (Hill i wsp., Nature Reviews Gastroenterology and Hepatology, 2014), and the second was updated by the ISAPP panel three years later.

The word that defines a probiotic is 'live'. Bacteria or yeasts, such as Saccharomyces boulardii, must survive the acidic environment of the stomach and reach the intestine in sufficient numbers, usually from 10⁸ to 10¹⁰ colony-forming units. The definition of a prebiotic is based on the word 'selectively': the substrate should feed beneficial bacteria, not every microorganism in the intestine, including pathogens. The condition of selectivity has been maintained panel ISAPP w dokumencie z 2017 roku, expanding the scope of the concept beyond carbohydrates and the digestive tract.

A postbiotic is the third tier of this structure, meaning the metabolites produced from fermentation. Butyrate, propionate, and acetate, along with lactic acid and some B vitamins. They can be delivered directly, bypassing fermentation, and this is exactly how sodium butyrate supplements work. A synbiotic, on the other hand, is a mixture of live microorganisms and a substrate selectively used by them, according to the ISAPP definition from 2020.

What types of prebiotics have the strongest data?

The best-documented are inulin and chicory fructooligosaccharides, enzymatically produced galactooligosaccharides from lactose, and resistant starch. Each of these groups feeds different bacteria, so diversity in the diet provides a broader effect than a single high-dose supplement.

Inulin and FOS mainly come from chicory root, Jerusalem artichoke, onions, and garlic. They stimulate the growth of Bifidobacterium and Lactobacillus. A reasonable range is 5-15 g daily, and above 15 g in sensitive individuals can cause bloating and gas, as fermentation kicks in rapidly. FOS has a lower degree of polymerization than long-chain inulin, so it ferments earlier and shallower, while the long chain reaches further in the colon.

GOS are produced from lactose under the influence of beta-galactosidase, and the final product does not contain free lactose. They support Bifidobacterium longum and B. breve. The same mechanism is utilized by the modified milk industry, where GOS serves as an analogue of human milk oligosaccharides. In adults, 4-8 g per day is often better tolerated than FOS at the same dose.

Resistant starch is divided into fractions. RS1 is physically inaccessible because it is found in whole grains. RS2 is raw starch with a dense structure, such as green bananas and raw potatoes. RS3 forms when cooked starch is cooled, so you will find it in cold rice and potatoes from the previous day. Its breakdown depends more on one species than on diet: Ze i wsp. (The ISME Journal, 2012) they showed that Ruminococcus bromii plays the role of a keystone species, and without it, other amylolytic bacteria ferment resistant starch to a very limited extent.

Why does butyrate determine the integrity of the intestinal barrier?

Butyrate is the primary fuel for colonocytes and also a signal that accelerates the assembly of tight junctions in the epithelium. Peng i wsp. (The Journal of Nutrition, 2009) they demonstrated in a Caco-2 cell model that butyrate increases transepithelial resistance and organizes tight junction proteins, and the effect disappears after blocking AMPK kinase.

It is produced by colonic bacteria, primarily Faecalibacterium prausnitzii, Roseburia intestinalis, and Eubacterium hallii. The substrate is fermentable fiber, so the supply of butyrate directly depends on how many prebiotics make it to your plate. This is the simplest explanation of why a probiotic supplement taken with a diet low in vegetables delivers less than the packaging promises.

Beyond the intestine, butyrate inhibits histone deacetylases, which are enzymes that regulate gene expression. Canani i wsp. (World Journal of Gastroenterology, 2011) they gathered evidence of its role in fluid transport across the epithelium and in alleviating mucosal inflammation, also mentioning extraintestinal effects in hypercholesterolemia and insulin resistance. The authors describe them as therapeutic potential, not as indications ready for use.

The cheapest way to increase butyrate production is a diet rich in resistant starch and inulin. An alternative is sodium butyrate supplement, a postbiotic administered bypassing fermentation. It has a characteristic smell that one needs to get used to, but it avoids the problem for those who cannot tolerate large amounts of fermentable fiber.

How does the microbiome affect mood through the gut-brain axis?

Gut bacteria communicate with the brain through the vagus nerve, the immune system, and fermentation metabolites. Cryan and Dinan (Nature Reviews Neuroscience, 2012) they described this bidirectional pathway and the mechanisms through which the microbiota modifies the response to stress and behavior. We break down the mechanisms of this axis into fundamental factors in a separate post about the influence of the microbiota on stress and sleep.

Clinical data are weaker than marketing suggests, and this needs to be stated plainly. The meta-analysis Ng i wsp. (Journal of Affective Disorders, 2018) included 10 studies involving 1349 participants and did not show an overall effect of probiotics on mood. Improvement was observed only in a subgroup of individuals with mild to moderate depressive symptoms, while no effect was noted in healthy individuals.

Individual studies with specific strains perform better. Messaoudi i wsp. (British Journal of Nutrition, 2011) they administered Lactobacillus helveticus R0052 together with Bifidobacterium longum R0175 for 30 days and noted a decrease in daily urinary free cortisol excretion and lower scores on the HSCL-90 and HADS scales.

On the prebiotic side, the results are more selective than they are usually summarized. Schmidt i wsp. (Psychopharmacology, 2015) they compared FOS, galacto-oligosaccharides B-GOS, and placebo over three weeks in 45 healthy volunteers. A lower morning cortisol response and less attention directed at negative stimuli were recorded only after B-GOS. There was no effect after FOS, so the type of prebiotic determines the outcome here.

When does a synbiotic work better than its individual components?

Wtedy, gdy substrat dobrano pod konkretny szczep. Panel ISAPP (Swanson i wsp., Nature Reviews Gastroenterology and Hepatology, 2020) referred to such a preparation as a synergistic synbiotic and distinguished it from a complementary one, where the probiotic and prebiotic simply sit next to each other in a capsule.

This distinction has practical significance when reading labels. A product described as "ten strains plus inulin" is usually a complementary synbiotic, and then each component must meet evidence requirements separately. A synergistic synbiotic sets a lower bar for individual components because its action is supposed to result from their cooperation, but it requires data for the entire mixture.

The choice of substrate for a strain is based on what that bacterium can break down. Bifidobacterium longum handles inulin well, so pairing it with inulin from chicory makes biochemical sense. Bacteria specialized in starch breakdown are more suited to resistant starch than to FOS. Which strain is suitable for what, we outline in the guide on choosing probiotics for gut health and immunity.

The ISAPP panel pointed out an uncomfortable truth for manufacturers: evidence for most ready-made synbiotics is still being gathered, and the mere presence of two components in the composition proves nothing. Treat the label "synbiotic" as information about the formula, not as a promise of effectiveness.

What really increases the abundance of Akkermansia muciniphila?

Akkermansia muciniphila lives in the mucus layer of the colon, and its low abundances are associated with obesity and insulin resistance. Plovier i wsp. (Nature Medicine, 2017) they showed in a mouse model that administering this bacterium, even pasteurized, reduces fat mass gain and insulin resistance.

The transfer to humans appears more cautious than the headlines suggest. Depommier i wsp. (Nature Medicine, 2019) They administered 10¹⁰ cells daily to individuals with overweight and insulin resistance for three months. The study was exploratory in nature and primarily demonstrated the safety of such supplementation, while the improvement of some metabolic markers was an additional result, not evidence of clinical efficacy.

Dietary tools are readily available and cost less. The mucus layer inhabited by this bacteria thrives on a diet rich in diverse fermentable fiber and polyphenols from vegetables, berries, and green tea. This is a valid argument for a wide range of prebiotics in the diet, rather than a single supplement with inulin.

We have noticed in conversations with readers that the name of this bacteria appears more frequently than any specific way of nourishing it. The order is often reversed: diet first, then any potential preparation.

Are prebiotics safe with IBS?

With irritable bowel syndrome, prebiotics can be both a problem and a help at the same time. The fermentation of oligosaccharides is one of the pain mechanisms in IBS, which is why a low FODMAP diet limits inulin, FOS, and GOS. However, this limitation is a diagnostic tool, not a target dietary approach.

The paradox is that long-term adherence to a low FODMAP diet depletes the microbiome, which can worsen the situation in the long run. The practice looks like this: an elimination phase for four to six weeks, followed by gradual reintroduction in small portions, for example, starting with 2-3 g of inulin daily, while observing symptoms. The individual tolerance threshold can be much higher than what is indicated in the first week of elimination.

In the case of ulcerative colitis and Crohn's disease, the situation is more complicated. Faecalibacterium prausnitzii, one of the main producers of butyrate, is significantly reduced in these patients, so the idea of feeding it with inulin seems logical. However, gastroenterological guidelines do not include prebiotics in the standard treatment, and during an active flare-up, experiments with fermentable fiber can exacerbate symptoms. Make decisions with a gastroenterologist, not based on a leaflet.

How to use probiotics and prebiotics in practice?

Take probiotics daily at a consistent time, and during antibiotic therapy, maintain a 2-3 hour gap from the antibiotic dose and continue for several weeks after its completion. Introduce prebiotics gradually, as bloating is caused by a sudden increase in fermentation, not the fiber itself.

The approach to dosing looks like this: start with 3-5 g of inulin or FOS daily and reach 10-15 g within 2-3 weeks. For GOS, the starting point may be lower, and tolerance better. The target fiber intake overall is 25-35 g daily, with the variety of sources counting more than the dose of a single ingredient.

• Por, cebula, czosnek i topinambur: inulina oraz FOS.
• Oats and barley: beta-glucans.
• Legume seeds: resistant starch with galacto-oligosaccharides.
• Cooked and then cooled rice and potatoes: resistant starch RS3.

Meta-analysis King i wsp. (British Journal of Nutrition, 2014) included 20 randomized studies and clearly shows what can be expected from probiotics in respiratory infections: shorter episodes of illness by less than a day and fewer days absent from work and school. The number of episodes did not change, so probiotics shorten the illness rather than protect against getting sick. What to take after the treatment itself, we gathered in the post about odbudowie flory jelitowej po antybiotyku.

What is available from the intestinal shelf at u Bucha?

The u Bucha catalog currently lists eight items related to the microbiome: seven Aura Care preparations and sodium butyrate as a postbiotic administered directly. Prices are sourced from the Store API of the shop, as of August 8, 2026. The last column converts the price to one serving for easier horizontal comparison.

The last column speaks more than the price on the shelf. The multi-strain Aura Care capsules cost 4.30 zł per day, as the daily serving is one capsule. Sodium butyrate at 0.33 zł per capsule plays in a different price league, but it serves a different purpose: it does not colonize the gut but provides a metabolite that would normally arise from fiber fermentation. Products containing inulin, namely the Energy, Weight Loss, and Kids variants, are complementary synbiotics according to the ISAPP definition from 2020.

Frequently Asked Questions

What are prebiotics?

A prebiotic is a substrate selectively used by the host's microorganisms, providing a health benefit (Gibson et al., Nature Reviews Gastroenterology and Hepatology, 2017). In practice, this is indigestible fiber: inulin, FOS from chicory, GOS from lactose, resistant starch from cooled potatoes, and pectins from apples.

What is the difference between a prebiotic and a probiotic?

A probiotic is live microorganisms administered in amounts that confer a health benefit to the host (Hill et al., Nature Reviews Gastroenterology and Hepatology, 2014). A prebiotic is food for these bacteria. The probiotic corresponds to the gardener, while the prebiotic corresponds to the fertilizer. A lasting change in the microbiome requires both, as the preparation alone without fiber in the diet has a short-term effect.

What is a synbiotic?

A synbiotic is a mixture of live microorganisms and a substrate selectively used by them (Swanson et al., Nature Reviews Gastroenterology and Hepatology, 2020). The ISAPP panel distinguished between a complementary variant, where the components act independently, and a synergistic one, where the substrate is tailored to a specific strain. The label on the package proves nothing.

Do probiotics help with low mood?

The evidence is weaker than marketing suggests. A meta-analysis by Ng et al. (Journal of Affective Disorders, 2018) included 10 studies and 1349 participants, finding no overall effect. Improvement occurred only in a subgroup with mild to moderate depressive symptoms, and there was no effect in healthy individuals.

When should you take a probiotic and when a prebiotic?

Take a probiotic daily at a consistent time, and during antibiotic therapy, 2-3 hours after the antibiotic dose and for several weeks after its completion. Take a prebiotic with meals, gradually increasing the dose from 3-5 g to 10-15 g over 2-3 weeks to avoid bloating from rapid fermentation.

Do prebiotics exacerbate IBS symptoms?

They can, as the fermentation of oligosaccharides is one of the pain mechanisms in IBS, which is why a low FODMAP diet restricts inulin, FOS, and GOS. However, elimination lasts four to six weeks and serves for diagnosis. They are then reintroduced in small portions, observing the tolerance threshold.

If you prefer to start with a ready-made product before restructuring your diet, you can find probiotics with prebiotics in the category supplements.

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 · Opublikowano: 2026-06-22 · Aktualizacja: 2026-08-08