Gut health & symptomsOne of 8 articles on the topic

Probiotics and prebiotics: effects and foods

Capsules from the chemist, yoghurt with cultures or simply more fibre? Probiotics are live bacteria, prebiotics are their food. Here's what the difference is, when a supplement really does something and which foods provide both.

Gregor AßlaberJoerg Hauke
Gregor Aßlaber, Saturo editor · ✓Fachlich geprüft von Joerg Hauke, Nutrition expert
Aktualisiert 29 October 2026 · 15 Min. Lesezeit · 51 Quellen
In 30 seconds
Kefir, Joghurt, rohes Sauerkraut, Topinambur, Lauch, Zwiebeln, Knoblauch und Artischocke auf einer Steinplatte
Both on one table: kefir, yoghurt and raw sauerkraut bring live cultures, while Jerusalem artichoke, leek, onion and garlic bring the inulin those cultures live on.

The key points in 30 seconds

Antibiotic-associated diarrhoea in children
19 → 8%

With a probiotic, the risk falls from 19 to 8% (Cochrane 2019). It's the best-supported benefit, and it only applies during the course of treatment.

Fibre per day
18g

is what the average woman in Germany eats. The average man gets 19 g. The DGE recommends 30 g. Prebiotics are part of that, not an extra.

Inulin in 100 g Jerusalem artichoke
17g

at least, measured raw. Garlic has 9 g, leek and onion 3 g. Most of the prebiotics in everyday diets come from vegetables and bread.

The most important rule
The strain

Whether a probiotic works depends on the exact strain and the dose, never on “probiotics” in general. “Probiotics help” isn't a reliable statement, and neither is the opposite.

01 Basics

Probiotics and prebiotics: what they are and how they work

Probiotics are live microorganisms. Prebiotics are indigestible food components that gut bacteria live on. One comes as a bacterium, the other as a fibre. Both have “biotic” in the name, and that's exactly what causes confusion, because in the supermarket, at the pharmacy and in research the terms mean different things.

What are probiotics?

According to the FAO and WHO definition, probiotics are live microorganisms that, in sufficient amounts, have a proven health benefit. Both conditions count: the bacteria have to arrive alive, and a benefit has to be shown in human studies for that exact strain. Most probiotics belong to the lactic acid bacteria (the Lactobacillus group) or the bifidobacteria, or are yeasts such as Saccharomyces boulardii. A strain is named with genus, species and a strain code, for example Lacticaseibacillus rhamnosus GG. If the code is missing, nobody knows which bacterium is really in there.

What are prebiotics?

Prebiotics are substances that gut bacteria specifically use and that bring a health benefit as a result, according to the 2017 consensus of the scientific society ISAPP. In practice, these are mainly certain fibres: inulin and oligofructose from chicory, Jerusalem artichoke, onion and garlic, galactooligosaccharides from pulses, and the resistant starch in cooled potatoes. They reach the large intestine undigested, where bacteria ferment them into short-chain fatty acids. Not every fibre is a prebiotic, but every prebiotic counts towards the 30 g of fibre the DGE recommends per day.
At a glance

Pro-, pre-, syn- and postbiotics compared

Four terms, four definitions from the scientific society ISAPP. The evidence column refers to human studies.

What it isExample foodExample supplementEvidence
ProbioticsLive bacteria or yeasts with a proven benefitYoghurt with an added strain, raw fermented vegetablesCapsules with L. rhamnosus GG, S. boulardiiGood for antibiotic-associated diarrhoea, IBS depending on the strain
PrebioticsFood for gut bacteria, mostly fibreJerusalem artichoke, onion, leek, pulsesInulin or oligofructose powderMore bifidobacteria, better gut function from 12 g of inulin
SynbioticsA probiotic plus a matching prebioticKefir with oats, not a product in itselfCombined capsules or powdersFew studies, hardly better than the individual parts
PostbioticsInactivated bacteria or their componentsNone, only made in the labHeat-inactivated bifidobacteriaFirst studies, no guideline yet

Definitions: Hill 2014 (probiotics), Gibson 2017 (prebiotics), Swanson 2020 (synbiotics), Salminen 2021 (postbiotics). Inulin effect: approved EU claim from 12 g of chicory inulin per day.

Synbiotics and postbiotics

Synbiotics combine both: a probiotic plus the prebiotic it lives on. Sounds logical, but it's rarely better supported than the individual parts, because most combinations have only been tested in a single study. Postbiotics are the newest term: killed bacteria or their components that are still supposed to work, for example through cell wall building blocks. The advantage is shelf life, because nothing is alive any more. The data is thin, and no guideline recommends them so far.

How probiotics work: strain-specific and temporary

The effect of a probiotic depends on the exact strain, the dose and the duration. The World Gastroenterology Organisation (WGO) states this as a basic rule: recommendations should be tied to specific strains with human studies, not to “probiotics” in general. There's also a second finding: in healthy people, the bacteria settle in only temporarily, and differently from person to person. In a study using colonoscopy, some participants stayed “resistant” to colonisation, and in others it was gone again after stopping. So a probiotic works for as long as you take it.

What a probiotic does in the gut comes down to three mechanisms: it competes with unwanted germs for space and nutrients, it produces lactic acid and other metabolic products that change the gut environment, and it communicates with the gut lining and the immune system behind it. Which mechanism matters differs from strain to strain. The timeline shows the journey from the first mouthful to stopping.
Kefir, plain yoghurt and raw sauerkraut: foods with live cultures
Kefir, plain yoghurt and raw sauerkraut bring live cultures. In the strict sense, they only count as probiotic once a specific strain is in there in an effective amount.
02 Understand

A probiotic's journey through your body

Three stages decide whether a probiotic arrives at all, what it does in your gut and why the effect disappears after you stop.

1

Stomach: the acid test

Stomach acid kills some of the bacteria. In a lab model, more of them survived when the capsule was taken with or shortly before a meal. Spore-forming strains and yeasts cope better with the acid, and gastro-resistant capsules bypass it.

2

Gut: passing through, not moving in

In the large and small intestine, the bacteria compete for space and nutrients, produce lactic acid and messenger substances, and meet the gut lining with the immune system behind it. In healthy people they rarely settle permanently, and the effect varies from person to person.

3

After stopping: gone again

A few days to weeks after the last dose, the strains usually can't be detected any more. Your own gut flora returns. That's why the benefit only lasts while you're taking them, and why it's worth looking at what feeds your own bacteria in the long term.

03 Putting it in context

Are probiotics worth it? What the studies show

For healthy people without symptoms, probiotics are generally not necessary, and for a few situations they're well supported. That's the short version of the guidelines and Cochrane reviews. The consumer advice centre goes even further: for foods with bacterial cultures, there's no evidence of a benefit for healthy people. Both are true, because they're about different groups: patients with a specific diagnosis and a specific strain on one side, healthy people with yoghurt on the other.

Probiotics for diarrhoea

Best supported is the prevention of diarrhoea during antibiotics: in children the risk falls from 19 to 8%, with nine children needing treatment for one to avoid diarrhoea; in adults the risk falls by 37%. For acute stomach bugs the picture is mixed: the European paediatric society allows two strains, the Cochrane analysis of low-bias studies finds no effect, and US gastroenterologists advise against them. For travellers' diarrhoea, a yeast preparation (S. boulardii) is approved as a medicine. If you have acute diarrhoea, you need fluids and salt first, not a probiotic.
Interactive

Do I need a probiotic?

Three questions, one pointer to the right chapter. Not a diagnosis, but the logic guidelines use to decide.

1Are you taking an antibiotic right now, or starting one in the next few days?

Not a diagnostic tool. Basis: S3 guideline on irritable bowel syndrome (DGVS 2021), ESPGHAN 2023, Cochrane 2019/2025, S. boulardii product information. If you have symptoms, get them checked by a doctor.

Probiotics for irritable bowel syndrome

The German S3 guideline recommends: “Selected probiotics should be used in the treatment of irritable bowel syndrome”, with a grade B recommendation. The key word is “selected”: the effect depends on the strain, the dose and the duration, and every attempt counts as a trial that is only continued if symptoms clearly ease. In the large meta-analysis, IBS symptoms persisted less often with probiotics (relative risk 0.79), and bloating and a feeling of fullness improved most reliably. The US professional societies are more cautious: the AGA recommends probiotics for IBS only within clinical trials, because 76 studies tested 44 different products and hardly any result was repeated. There is no recommendation for prebiotics in IBS; inulin and oligofructose are FODMAPs and often make bloating worse.

In functional constipation, probiotics shortened gut transit time by 12 hours in one meta-analysis and brought 1.3 more bowel movements per week, but this was only significant for Bifidobacterium lactis. For children with constipation, the European professional society advises against probiotics because they don't work.

A probiotic isn't a cure-all, it's a tool for a specific situation: the right strain, the right dose, the right timing. For everything else, your plate is the better place to look.

Joerg Hauke, Nutrition expert, technical review of this article

Probiotics for the immune system, skin and weight loss

This is where the evidence gets thin, and to be honest, thinner than the advertising makes it sound. Immune system: In the Cochrane review, people taking a probiotic got a respiratory infection less often (relative risk 0.76) and were ill for 1.2 days less on average, with low-certainty evidence and with use over more than three months. That's prevention, not a remedy for a cold you already have. Skin: According to Cochrane, there is no evidence that probiotics work as a treatment for atopic eczema, and the German guideline on allergy prevention advises pregnant women and infants against pro- and prebiotics for prevention, with a grade A recommendation. Weight loss: In 15 studies with overweight people, probiotics brought 0.6 kg less weight in three months. If you want to lose weight, the article Losing weight covers the levers that really make a difference.
04 Antibiotics

Probiotics and antibiotics: yes during, usually not after

Antibiotics are the most common reason people look for probiotics, and the case where the order makes all the difference. During the course, the benefit is proven; afterwards, it isn't.

Probiotics during antibiotics

Taken at the same time, certain strains clearly lower the risk of antibiotic-associated diarrhoea: from 19 to 8% in children, by 37% in adults. The ones that worked were mainly Lacticaseibacillus rhamnosus GG and the yeast Saccharomyces boulardii, and only from about 5 billion CFU a day. You start on the first day of the course, not only once your stomach starts rumbling: in an analysis of hospital patients, the risk of a Clostridioides difficile infection only dropped if the probiotic was started within two days of the first antibiotic. There's no proven minimum gap between probiotic and tablet; the yeast doesn't interfere with the antibiotic anyway, and for bacterial products, follow the instructions in the package leaflet.

Probiotics after antibiotics

After the course has ended, a benefit is not proven. No guideline recommends probiotics to “rebuild” your gut flora afterwards, and a small Israeli study using colonoscopy found the opposite: in participants who took a multi-strain product after the antibiotic, their own gut flora recovered more slowly and stayed less complete than in those who did nothing. The study is small and only measures the microbiome, not symptoms, so it doesn't prove harm. But it shows that “it can't hurt” isn't a safe assumption.

What really helps after a course is food for your own bacteria: Rebuilding your gut flora explains step by step what happens in the weeks afterwards and which foods support recovery. The short version: plenty of vegetables, pulses and wholegrains, plus yoghurt or kefir if you tolerate them.
When to see a doctor

Watery diarrhoea more than three times a day during or up to eight weeks after a course of antibiotics, fever, blood in your stool or cramping stomach pain: get it checked out. It could be an infection with Clostridioides difficile, which needs treatment.

05 Prebiotics

Prebiotics: inulin, resistant starch and which foods provide them

You don't need to buy prebiotics. You're probably already eating them, just not enough. Average fibre intake in Germany is 18 g (women) and 19 g (men) a day, and 75% of women and 66% of men fall short of the recommended 30 g. Prebiotic fibres are the part of that fibre which gut bacteria ferment fastest.

Prebiotic foods

The most important prebiotics in everyday eating are inulin and oligofructose (fructans) from onion, garlic, leek, artichoke, Jerusalem artichoke and wheat, galactooligosaccharides from lentils, beans and chickpeas, and resistant starch, which forms when cooked potatoes, rice or pasta cool down. In the Western diet, around 70% of inulin comes from wheat and 25% from onions, simply because both are on our plates every day. Beta-glucan from oats and barley is also fermented, but its authorised benefit relates to cholesterol, not the gut. The WGO still lists resistant starch as a candidate, not an established prebiotic. Cooked and cooled potatoes contain measurably more of it than hot ones.

Inulin and oligofructose: per 100 g and per portion

  1. Jerusalem artichoke (17 to 20.5): 17 g
  2. Garlic (9 to 16): 9 g
  3. Onion (3.1 to 5): 3.1 g
  4. Leek, white part (3 to 10): 3 g
  5. Artichoke (2 to 7): 2 g
  6. Wheat, wholegrain (1.5 to 2.3): 1.5 g
  7. Banana, ripe (0.6 to 1.1): 0.6 g
  8. Barley (0.5 to 1.5): 0.5 g
  9. Rye (0.5 to 1): 0.5 g

Bars = lower end of the range in the literature per 100 g raw, full range in brackets (Canazza 2025, after Van Loo 1995). Inulin isn't listed in standard nutrition tables: the USDA lists Jerusalem artichoke with 1.6 g of fibre because the standard method doesn't pick up inulin.

Which foods contain inulin?

Most inulin is found in Jerusalem artichoke and chicory root, with 15 to 20 g per 100 g, followed by garlic with 9 to 16 g, leek with 3 to 10 g, artichoke with 2 to 7 g and onion with 3 to 5 g. Wheat has 1.5 to 2.3 g, while banana and rye have less than 1 g. These values are for raw foods. Inulin stays stable when cooked up to 100 °C, but it's broken down when acid and heat combine, and pickling and preserving reduce the content the most. Industrial inulin is extracted from chicory root and appears as “fibre (chicory)” in many foods, including the Saturo drinkable meal with 7.3 to 7.7 g of fibre per bottle.

Prebiotics: side effects

The typical side effects are bloating and wind, because that's exactly what fermentation produces. In a study with healthy adults, 10 g of chicory inulin and 5 g of oligofructose a day were well tolerated, while 10 g of oligofructose caused clearly more discomfort. The German Nutrition Society (DGE) advises increasing your fibre intake slowly and drinking enough fluids. If you're sensitive to FODMAPs or have irritable bowel syndrome, you may often tolerate inulin, oligofructose and GOS poorly. That's why the irritable bowel syndrome guideline makes no recommendation for prebiotics. Our article on fibre shows how to reach 30 g without discomfort.
Jerusalem artichoke, leek, onions, garlic and artichoke: foods high in inulin
Jerusalem artichoke, leek, onion, garlic and artichoke provide the fructans that bifidobacteria live on. For most people that's enough, and you don't need a powder.
06 Food

Probiotic foods: where to find live cultures

Yoghurt, kefir, sauerkraut, kimchi, kombucha: they're all fermented, but not all of them contain live cultures, and none is automatically a probiotic. The difference lies in how it's made and what's on the label.

Natural probiotics

Strictly speaking, there's no such thing as “natural probiotics”. Under the ISAPP consensus, a fermented food only counts as probiotic if it contains a characterised strain in an effective amount until the end of its shelf life and its benefit has been proven. Hardly any supermarket product meets that. Legally, the term is off-limits anyway: in the EU, “probiotic” counts as a health claim, and of more than 300 applications reviewed, EFSA hasn't approved a single one. In 2014, Germany's Federal Court of Justice confirmed this for “probiotic” on baby food too. What fermented foods can still do was shown by a Stanford study: six portions a day increased gut flora diversity over ten weeks and lowered 19 inflammation markers in the blood. There's also an authorised claim for yoghurt with live cultures: it improves the digestion of the lactose it contains in people with lactose intolerance.
Interactive

Is it probiotic?

Type in a food or filter by group. Green: contains live cultures. Yellow: depends on the product and how it's prepared. Red: no live cultures, even if it's fermented.

  • Plain yoghurt Yes, if not heat-treatedAt least 10 million starter cultures per gram until the best-before date (Codex). Chilled aisle; “heat-treated” on the pack means none.
  • Yoghurt with added strains L. acidophilus, Bifidobacterium Yes, amount varies widelyAdded strains sometimes drop below the effective amount by the best-before date. A strain name with its code is the quality marker.
  • Greek yoghurt Usually yes, check the packStrained yoghurt with the same starter cultures; none if heated after fermentation. Greek-style made from cream may be produced differently.
  • Skyr Yes, if soured with culturesSkyr is made with cultures, like yoghurt. A “live cultures” note or the cultures in the ingredients list give you certainty.
  • Quark Topfen Soured with cultures, amount unclearMade with lactic acid bacteria; cell counts in shop-bought products are barely studied. Not proven as a probiotic.
  • Kefir milk kefir Yes, bacteria and yeastsCodex: at least 10 million starter cultures and 10,000 yeasts per gram. Buy it chilled and unheated.
  • Buttermilk Yes in the chilled aisle, no if long-lifeCultured buttermilk is soured with cultures; UHT, unchilled versions contain none.
  • Thick milk, sour milk Dickmilch, Sauermilch Usually yesThickened with lactic acid bacteria; only heated long-life products have none.
  • Soured cream, Schmand, crème fraîche Usually yesAccording to ISAPP, soured cream and the like contain live cultures unless heat-treated. They die when cooked.
  • Cottage cheese, cream cheese Depends on the productMade with cultures, but often heated or pasteurised after ripening. Check the ingredients list.
  • Matured cheese Gouda, Tilsiter, Camembert Usually yes, if not heatedUp to 1 billion microbes per gram, most at 2 to 4 months of ripening (Tilsiter). Baked or melted: none.
  • Parmesan, Grana Padano, Gruyère matured over 1 year Below the detection limitIn long-matured hard cheese, counts in measurements were below 1,000 per gram.
  • Processed cheese No, heatedProcessed cheese is heated during production, and cultures don’t survive that.
  • Ayran, lassi Depends on the productYoghurt-based, so with cultures, unless the drink has been made long-life. Freshly mixed: yes.
  • Yoghurt drink with cultures drinking yoghurt Yes, check the strainChilled drinking yoghurts contain starter cultures and often added ones. A proven benefit only applies to the named strain.
  • Long-life yoghurt, unchilled No, heat-treatedYoghurts and fruit yoghurts that keep unchilled on the shelf are heated after fermentation.
  • Milk, pasteurised or UHT NoMilk isn’t fermented, and heating removes microbes. Raw milk contains bacteria, but no cultures with a proven benefit.
  • Sauerkraut, raw chilled aisle, barrel, market Yes1,000 to 100 million lactic acid bacteria per gram; “unpasteurised” or “raw” on the label.
  • Sauerkraut from a tin or jar No, pasteurisedSauerkraut that keeps unchilled is heated. Fibre stays, cultures don’t.
  • Kimchi Yes if unheated, no if cookedFresh kimchi delivers 10 to 100 million microbes per gram. Pasteurised shop-bought kimchi and kimchi stew: none.
  • Sour pickles, lactic-fermented salt-brined gherkins Yes, if vinegar-free and chilledReal brined gherkins ferment in salt brine. Look for an ingredients list without vinegar, in the chilled aisle.
  • Vinegar gherkins, pickled gherkins No, not fermentedVinegar, sugar and heating: no fermentation, no cultures.
  • Olives Depends on the methodOlives are fermented in brine, but shop-bought ones are mostly pasteurised. Loose ones from the deli counter are more likely to contain cultures.
  • Jerusalem artichoke, onion, garlic, leek Prebiotic, not probioticNo cultures, but the top inulin sources. They feed the bacteria that are already there.
  • Kombucha Usually yes, some are pasteurisedCommercial kombucha contains 1 to 10 million acetic acid bacteria and yeasts per millilitre; filtered or pasteurised types don’t.
  • Brottrunk, kvass Yes if fresh, no if pasteurisedFermented bread drink with lactic acid bacteria and yeasts. A proven health benefit is lacking (FAQ).
  • Apple cider vinegar NoAccording to ISAPP, vinegar is one of the foods without live microorganisms; the vinegar mother doesn’t change that in any proven way.
  • Beer Mostly noFiltered and pasteurised. Only unfiltered, unheated beers still contain yeasts.
  • Wine NoYeasts are removed; wine counts as a food without live microorganisms.
  • Water kefir Yes, if home-madeFermented sugar water with bacteria and yeasts; shop-bought versions are often pasteurised.
  • Sourdough bread No, bakedThe cultures from the dough die in the oven. The benefit lies in the fermentation, not in live microbes.
  • Rolled oats Prebiotic, not probioticNo cultures, but beta-glucan and fibre. Combine them with yoghurt or kefir and you get a breakfast with both.
  • Muesli, wholemeal bread Prebiotic, not probioticWheat and rye provide fructans, wholemeal bread up to 0.6 g per serving. Live cultures: none.
  • Lentils, beans, chickpeas Prebiotic, not probioticGalactooligosaccharides and resistant starch, no cultures. The strongest prebiotic suppliers after vegetables.
  • Potatoes, rice, pasta, cooled Prebiotic, not probioticCooling creates resistant starch, and chilled potatoes contain measurably more than hot ones. No cultures.
  • Miso Yes if unpasteurised, no in hot soupUnpasteurised miso paste contains fungal and bacterial cultures. Stirred into boiling soup, they’re gone.
  • Tempeh Yes if raw, no if friedFresh tempeh contains mould and up to 1 billion lactic acid bacteria per gram. Pasteurised or fried tempeh: none.
  • Natto YesSoybeans fermented with Bacillus subtilis, containing live microorganisms according to ISAPP. Rare in Germany.
  • Soy sauce NoFermented, but heated and filtered after fermentation.
  • Tofu No, not fermentedTofu is curdled from soy milk, not fermented. Fermented tofu (sufu) is a different product.
  • Salami, air-dried Yes if raw cured, no if heatedUnheated raw sausage contains live starter cultures according to ISAPP; cooked sausage and boiled ham don’t.
  • Chocolate, cocoa NoCocoa beans are fermented, then roasted. Nothing is alive in the bar.
  • Supplements with bacterial cultures capsules, powders Depends on the productAlive if the cell count holds until the end of shelf life and storage is right. Some products fell short of their claims in tests.
Classification based on the ISAPP consensus on fermented foods (Marco 2021), Rezac 2018 (cell counts in shops) and Codex Standard 243 for fermented milks. Live cultures are no proof of an effect; that has only been shown for individual strains. Not medical advice.

Probiotic yoghurt: skyr, Greek yoghurt, kefir

Every yoghurt that hasn't been heat-treated contains live cultures, at least 10 million starter bacteria per gram up to the best-before date. That goes for natural yoghurt, Greek yoghurt and skyr alike, because they're all soured with the same cultures. Skyr and Greek yoghurt are just strained more, so they give you more protein. Kefir also brings yeasts, with up to a billion microbes per gram. "Probiotic yoghurt" in the strict sense is only one with an added, named strain, and even then the added strains often drop sharply by the best-before date. Fermented foods are also rich in histamine. If you react to it, you'll probably struggle with sauerkraut, mature cheese and kombucha.

Between foods with cultures and capsules there's a third group: meals with a bacterial strain added as an ingredient. According to the WGO, spore-forming strains such as Bacillus coagulans are more resistant to heat and storage, but the evidence for them is weaker than for lactobacilli and bifidobacteria. The same applies here: a strain in the ingredients list is an ingredient, not a promise of results.
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If you want to combine probiotics and prebiotics from food, you don't need a special product: natural yoghurt or kefir with oats and banana, raw sauerkraut with lentils, kimchi with yesterday's rice. The cultures come from the fermented food, the fuel from grains, pulses and veg. Which ten foods do the most for your gut is covered in the gut overview.
Woman spooning raw sauerkraut from the jar onto a plate of lentils
Raw sauerkraut with lentils: live cultures plus galactooligosaccharides on one plate, with no label needing to promise "probiotic".
07 In practice

Taking probiotics: timing, duration, choice and side effects

Once you've decided on a supplement, three things determine how much you get out of it: the strain, the dose and the duration. The time of day matters less than the leaflets suggest.

Taking probiotics: morning or evening?

The time of day isn't what counts, but the meal is. There are no human studies on "morning or evening". In a lab model of the stomach, the bacteria from a capsule survived best when taken with a meal or 30 minutes before, and worst 30 minutes after. A little fat in the food helped, while apple juice and water alone helped less. Yeast supplements didn't depend on timing. In practice that means: with breakfast or dinner, as long as you take them regularly. There's no ban on coffee, but you shouldn't stir them into drinks hotter than 50 °C.

How long should you take probiotics?

As long as the use the strain has been shown for. For a course of antibiotics, for the length of the course. For acute diarrhoea, 5 to 7 days. For irritable bowel, 4 to 8 weeks as a trial, followed by an honest review. For preventing infections, the studies ran for more than three months. Taking them long term "for your gut flora" hasn't been shown to help healthy people, and after you stop, the strains disappear within days to weeks anyway.

Probiotics from the chemist or pharmacy

The difference isn't on the shelf but in the legal status: most probiotics are food supplements, whether they're sold at dm, Rossmann or a pharmacy. They aren't allowed to name a disease and aren't tested for effectiveness. A few products are licensed medicines with a defined use, such as the yeast Saccharomyces boulardii for acute diarrhoea, or the strain E. coli Nissle 1917 for ulcerative colitis in remission and chronic constipation. Those are only available in pharmacies, with professional information, contraindications and a tested microbe count. Capsule or powder is a matter of taste, as long as the microbe count is guaranteed until the end of shelf life. The list shows how to recognise a decent product.
Interactive

How to spot a reputable product

Tap what applies to the product. You'll then see how many quality criteria it meets.

Criteria based on the WGO guideline 2023 and the S3 guideline for irritable bowel syndrome. Not a product recommendation; if you have a medical condition, the choice belongs in the hands of a doctor or pharmacist.

Is there a probiotics test winner?

No, there is no current test of probiotic capsules by Stiftung Warentest or Öko-Test. The closest thing is the test of over-the-counter remedies for irritable bowel syndrome (issue 01/2022): the reviewers rated 13 of 19 products, including several with bacterial cultures, as “not very suitable” and none as suitable. The Verbraucherzentrale (consumer advice centre) sums up the 2026 position like this: advertising claims for foods with bacterial cultures are not scientifically proven, and therapeutic use belongs in a doctor's hands. Online rankings mostly compare prices and bacteria counts, not studies, and are often paid for by shops. The only “test winner” that counts is the strain that has been studied for your question.

Probiotics side effects

For healthy people, common probiotics are considered safe; in the Cochrane reviews, side effects were no more common than with placebo. What does happen is bloating, stomach cramps, loose stools and nausea, usually mild. One medicine manufacturer advises spreading the daily dose across your meals if you get bloating. Unlike with prebiotics, there's no specific evidence for “initial bloating” that fades after a few days. Serious side effects almost exclusively affect people with a severe pre-existing illness.
Capsule next to a glass of water and a bowl of yoghurt on a breakfast table
Taken with breakfast, more bacteria survive the journey through the stomach than on an empty stomach. What matters more than the time of day is that the strain fits your question.

Who shouldn't take probiotics?

People with a severely weakened immune system, the seriously ill and patients with a central venous catheter should not take probiotics, according to the contraindication in the product information for the yeast preparation and the WGO recommendation. The reason: the bacteria or yeasts can get into the blood. In a review of 117 cases of yeast bloodstream infection, two thirds started with an S. boulardii product, almost always in intensive care patients or people on artificial feeding. For premature babies, the US medicines regulator issued a warning about probiotics in 2023 after a death. For an acute stomach bug, the Verbraucherzentrale advises against them, and for short bowel syndrome the decision belongs in hospital.

Pregnant and breastfeeding women: according to a review of 100 studies, probiotics and prebiotics are considered safe, individual medicines are not approved due to a lack of data, and the German guideline clearly advises against them for preventing allergies. Babies and toddlers: in 2026, the German Federal Institute for Risk Assessment saw neither harm nor proven benefit in infant formula with added bacteria for healthy babies; only use products after talking to a paediatrician.
Good to know

Microbiome stool tests from the internet can't tell you whether you need a probiotic. The irritable bowel guideline knows of no validated approach for this, Stiftung Warentest calls the analyses “expensive and meaningless”, and almost half of the providers sell you the matching capsules as well.

08 Look it up

Common questions about probiotics and prebiotics

Which probiotic is the best?

The one whose strain has been studied for your question. For antibiotic-associated diarrhoea, L. rhamnosus GG and S. boulardii at 5 billion CFU a day or more have the best evidence; for irritable bowel, several strains, tried over 4 to 8 weeks. There is no single best probiotic for everyone.

Can you take probiotics and prebiotics together?

Yes, together they're called a synbiotic. An added benefit over the individual parts is rarely shown. In everyday life, the combination on your plate is enough: yoghurt or kefir with oats and banana, raw sauerkraut with pulses.

Is Greek yoghurt probiotic?

It contains live cultures like any unheated yoghurt, at least 10 million per gram until the best-before date. In the strict sense, it would only be probiotic with an added, named strain and a proven benefit. On the pack: not “heat-treated”.

Are oats prebiotic?

Oats provide beta-glucan and about 4 g of fibre per 40 g, which gut bacteria ferment. Beta-glucan isn't classed as a prebiotic in the narrow sense; its approved benefit relates to cholesterol. Oats contain hardly any fructans, just 0.1 g per portion.

Which drink is good for your gut flora?

Kefir and buttermilk from the chiller aisle bring live cultures with them, and kombucha usually does too. For none of them is a benefit proven in healthy people. Water matters most, especially if you're increasing your fibre, otherwise constipation and bloating are likely.

How long should you avoid coffee after probiotics?

You don't need to wait at all. No guideline or product information has a rule on this. All that's proven is that bacteria survive the journey through the stomach better with or shortly before a meal. Don't use hot drinks above 50 °C to stir in powder.

How can I test whether my gut flora is OK?

You can't, not reliably. Commercial microbiome stool tests aren't standardised or validated, and there's no agreement on what a healthy gut flora is. If you have symptoms, what counts is a medical check-up, not a list of bacteria.

What effect does Brottrunk have?

Brottrunk is a bread drink fermented with lactic acid bacteria; fresh, it contains live cultures, pasteurised it doesn't. A health benefit hasn't been proven in human studies. If you like it, drink it as a sour drink, not as a therapy.

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Gregor Aßlaber
Gregor AßlaberAuthor · Editor at Saturo

Has been writing for Saturo since 2019 about nutrition, nutrients and how to get good nutrition in practice in everyday life.

Joerg Hauke
Joerg HaukeFachliche Prüfung · Nutrition expert

Hat diesen Artikel am 29. Oktober 2026 auf fachliche Richtigkeit geprüft. This content is not a substitute for medical advice.

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