Postbiotics are preparations of inactivated (dead) microorganisms or their cell components that confer a health benefit on the person who takes them[1]. Heat-killed bacteria, pasteurized Akkermansia and bacterial lysates qualify. Purified butyrate, cell-free filtrates and other purified microbial compounds do not, even though many articles still call them postbiotics[1].
The human evidence is real but narrow. A handful of specific, named preparations have randomized trials behind them, mostly for IBS, childhood infections and colds, and the results apply to those exact strains, not to "postbiotics" as a category[2][3].
This guide covers the official definition, real examples, how postbiotics may work, what the trials found, the foods that contain them, how to judge a supplement and who should be careful.
What are postbiotics, and are they a real thing?
Yes. Postbiotics are a recognized scientific category with a consensus definition. A postbiotic is "a preparation of inanimate microorganisms and/or their components that confers a health benefit on the host", the definition set by an International Scientific Association for Probiotics and Prebiotics (ISAPP) expert panel in 2021[1]. The preparation must contain inactivated microbial cells or cell parts, with or without the metabolites they made[1].
That places postbiotics alongside the two older terms. A probiotic is a live microorganism that benefits health in adequate amounts[4], and a prebiotic is a substrate that host microbes selectively use to confer a benefit[5]. For the full comparison of the three, see our prebiotics vs probiotics guide, and for the live organisms themselves, see what probiotics are.
Researchers previously used several names for the same idea: paraprobiotics, ghostbiotics, non-viable probiotics and heat-inactivated probiotics[6]. Postbiotics is now the umbrella term. The starting microbe does not have to be a recognized probiotic while it was alive[1].
What counts as a postbiotic, and what does not
| Counts as a postbiotic | Does not count on its own |
|---|---|
| Whole microbes inactivated by heat, pressure, radiation or drying | Purified short-chain fatty acids such as butyrate |
| Broken cells and cell wall fragments (lysates) | Filtrates or "supernatants" with no cell components |
| Inactivated cells plus the metabolites they produced | Isolated proteins, peptides or exopolysaccharides |
| Preparations applied to the gut, mouth, skin, nose or urogenital tract | Vaccines, bacteriophages and lab-synthesized compounds |
The ISAPP panel lists every item in the right-hand column as outside the definition, although they may be present inside a postbiotic preparation[1]. A postbiotic also has to be given at a body surface such as the gut, oral cavity, skin, nasopharynx or urogenital tract[1].
Why older articles call short-chain fatty acids postbiotics
Before 2021, "postbiotic" was used loosely for almost any bioactive fermentation product, including the short-chain fatty acids (SCFAs) your gut bacteria make from fiber[6]. The ISAPP panel narrowed the postbiotic meaning and decided that SCFAs used as purified substances are not postbiotics[1]. Butyrate still matters for gut health. A sodium butyrate capsule is simply a metabolite supplement, judged on its own evidence.
Postbiotic examples you will actually see
These are the main postbiotic types that have reached people, either in trials or on shelves.
| Example | What it is | Where it appears |
|---|---|---|
| Heat-inactivated Bifidobacterium bifidum MIMBb75 | Whole cells killed by heat | IBS supplement tested in a 443-person trial[3] |
| Pasteurized Akkermansia muciniphila | Gut bacterium inactivated by pasteurization | Authorized EU novel food for adults[7] |
| Lacticaseibacillus paracasei CBA L74 fermented milk or rice | Food fermented, then heat-treated | Tested in daycare children[8] |
| Fermented infant formula (Bifidobacterium breve C50 and Streptococcus thermophilus) | Formula fermented, with no live bacteria left | Sold for formula-fed infants[9] |
| Bacterial lysates such as OM-85 | Broken-down cells of respiratory bacteria | Authorized medicines in the EU[10] |
The panel lists heat treatments (pasteurization, tyndallization, autoclaving), high pressure, ultrasonication, ionizing radiation, pulsed light, spray drying and oxygen exposure among the ways to inactivate microbes[1]. Because the method changes the cell's structure, a product must describe its inactivation process to meet the definition[1].
What do postbiotics do in the body?
Dead microbes cannot colonize or multiply, so postbiotics are thought to act through their structures and the compounds they carry. The ISAPP panel proposed five mechanisms[1]:
- Modulating the resident gut microbiota.
- Strengthening the epithelial barrier that lines the gut.
- Adjusting local and whole-body immune responses.
- Shifting systemic metabolic responses.
- Signaling through the nervous system.
Cell components such as peptidoglycan, surface proteins, exopolysaccharides and lipoteichoic acid are known to interact with immune cells, though most of that evidence comes from animal and lab studies[11]. Which mechanism drives a given result in people is usually not established.
Postbiotics benefits: what human trials show
The strongest evidence covers four areas: IBS symptoms, childhood infections, colds in older adults and metabolic markers. Each result belongs to one named preparation.
| Preparation | Trial | Result |
|---|---|---|
| Heat-inactivated B. bifidum MIMBb75, 1 billion cells daily | 443 adults with IBS, 8 weeks | 34% met the pain-and-relief endpoint vs 19% on placebo[3] |
| Heat-killed Lactobacillus acidophilus LB | 4 trials, 224 children with diarrhea | Diarrhea about 20 hours shorter[2] |
| Heat-inactivated L. paracasei CBA L74 | 2 trials, 537 children | Risk of diarrhea roughly halved (RR 0.51)[2] |
| Heat-killed Lactobacillus pentosus b240 | 280 older adults, 20 weeks | Colds in 29.0% (high dose) vs 47.3% on placebo[12] |
| Pasteurized A. muciniphila | 32 adults with insulin resistance, 3 months | Insulin sensitivity up 28.6%; weight change not significant[13] |
Gut symptoms and IBS
In the largest postbiotic trial in IBS, adults took two capsules of heat-inactivated B. bifidum MIMBb75 once a day for 8 weeks[3]. Abdominal pain and overall relief improved in 74 of 221 people versus 43 of 222 on placebo (risk ratio 1.7)[3]. The manufacturer funded the trial, and it has not yet been replicated at the same scale.
Infections in children and colds in older adults
A 2020 systematic review of seven trials in 1,740 children under five found that heat-killed L. acidophilus LB shortened diarrhea and that heat-inactivated L. paracasei CBA L74 lowered the risk of diarrhea, pharyngitis and laryngitis[2]. The authors still judged the evidence too limited to recommend specific postbiotics[2].
In one daycare trial of 377 children, 51.8% of children drinking the fermented milk had at least one infection over a winter, versus 80.3% on placebo[8]. In older adults, heat-killed L. pentosus b240 had already been shown to raise salivary secretory IgA, an antibody that guards the mouth and airways[12]. In the 20-week trial, it lowered common cold incidence in a dose-dependent way[12].
Bacterial lysates are already authorized as medicines in Europe. In 2019 the European Medicines Agency restricted them to preventing recurrent respiratory infections, because there were no robust data for treating existing infections or preventing pneumonia[10]. A 2024 analysis of nine systematic reviews on the lysate OM-85 in children found results too heterogeneous for strong recommendations[14].
Metabolic health and weight
Pasteurized Akkermansia improved insulin sensitivity by 28.6% and lowered total cholesterol by 8.7% versus placebo in a 32-person pilot study[13]. A 2026 trial in 142 adults with metabolic syndrome then found no difference in its primary insulin resistance endpoint after 4 months[15]. Benefits appeared only in an exploratory subgroup with low starting Akkermansia levels[15].
Skin and exercise
A 2026 systematic review of 33 acne studies, seven of them on postbiotics, reported a pooled lesion reduction of 49.5% with postbiotics versus 37% in controls, with no serious adverse events[16]. The authors rated probiotics as having the stronger evidence base[16]. For athletes, a review of 11 small trials (477 people) found early signs of better mood and less fatigue, but no firm performance benefit[17].
Infant formula with postbiotics
Formulas fermented with B. breve C50 and S. thermophilus are the most studied, and an 11-trial review found them safe and well tolerated, with no firm conclusion on clinical benefit[9]. A meta-analysis of nine trials found no change in colic, diarrhea or growth[18]. In 2025 the European pediatric gastroenterology society (ESPGHAN) concluded that these formulas raise no safety concerns but made no recommendation for or against most biotics, including postbiotics[19]. For more on young children, see probiotics for kids.
Postbiotics vs probiotics: which is better?
Neither is better across the board. Each product stands or falls on trials of its own strain and preparation[1]. Non-viable cells may be easier to keep stable and standardize, and they avoid infection concerns in people prone to infection[3]. Probiotics have the larger evidence base, as the acne review found[16].
| Postbiotic | Probiotic | |
|---|---|---|
| Alive? | No: inactivated cells or cell parts[1] | Yes: live microorganisms[4] |
| Can it multiply or cause bloodstream infection? | No, because cells cannot replicate[1] | Live cells raise safety concerns in people prone to infection[3] |
| What the label must describe | Strain, inactivation method and composition[1] | Live microbes in an adequate amount[4] |
| Evidence base | A few strain-specific trials | Many trials, still strain-specific |
The two overlap more than marketing suggests. Probiotic products can contain inactivated cells, and at least one strain has shown the same benefit whether live or inactivated[6]. The IBS trial above used a strain that had already been studied as a live probiotic[3].
What foods are high in postbiotics?
Fermented foods contain dead microbes, microbial cell parts and fermentation products, and some contain no live microbes at all because they are baked, pasteurized or filtered after fermentation[11]. Examples of the second group include sourdough and other breads, pasteurized sauerkraut and pickles, soy sauce, vinegar, some kombuchas, and most beers and wines[11].
Whether eating these foods delivers a postbiotic benefit has not been tested the way named preparations have. ISAPP's fermented-food panel expects any immune effects to come from the combined starting ingredients, fermentation products, and living and dead microbes[11]. Unpasteurized fermented foods such as live-culture yogurt and kefir can supply both living and dead microbes[11]; see our probiotic foods guide for options.
Are postbiotic supplements worth it?
Only if the product names a preparation with human evidence for the outcome you care about. A product that contains only butyrate or a cell-free filtrate may be labeled "postbiotic", but it does not meet the scientific definition[1].
Check the label for the points the ISAPP panel says a postbiotic needs[1]:
- The exact strain, with a strain code (for example B. bifidum MIMBb75), not just a species name.
- How it was inactivated, such as heat or pasteurization.
- What it contains, as a cell count per dose that you can compare with the trial.
- A human trial on that preparation for your goal, not a general study on postbiotics.
Pasteurized Akkermansia is a useful benchmark: the EU authorized it after a safety review that set a limit of 34 billion cells a day and required fewer than 10 live colony-forming units per gram[7]. For more on what is actually available in this category, see next-generation probiotics you can buy.
Are postbiotics safe?
Postbiotics are expected to be safer than probiotics because their microbes cannot replicate, so they cannot cause bloodstream infection[1]. In the IBS trial, side effects were no more common than with placebo and no serious events occurred in the postbiotic group[3]. In infant formula, nine trials found no rise in serious adverse events[18].
Safety cannot be assumed from the starting microbe, though. Lipopolysaccharide (LPS) released from dead Gram-negative bacteria can trigger sepsis and toxic shock, so each postbiotic needs its own safety assessment for its intended use[1]. The EFSA safety opinion on pasteurized Akkermansia excluded pregnant and breastfeeding women[7]. If you are immunocompromised, critically ill, pregnant or choosing a product for an infant, ask your clinician before starting one.
This article is for general educational purposes and is not medical advice. Postbiotic results are specific to the strains and preparations tested, and they do not replace diagnosis or treatment of a digestive, metabolic or respiratory condition. Talk to a qualified healthcare professional before starting a postbiotic supplement, particularly if you are pregnant, immunocompromised, taking prescription medication, or managing a diagnosed condition.
Frequently Asked Questions
What is a postbiotic drink?
It is a drink marketed as containing a postbiotic ingredient. Whether it really does depends on what is in the can. Under the 2021 ISAPP definition, a product only qualifies if it contains inactivated microbial cells or cell components and the specific preparation has been shown to benefit health. A drink that adds purified butyrate or a filtered ferment without cell parts does not meet that definition. Check the label for the named strain and the amount, then look for a human trial on that exact preparation.
Do postbiotics make you poop?
Not in a laxative sense. The best-known gut trial used heat-inactivated Bifidobacterium bifidum MIMBb75 in 443 adults with IBS and measured abdominal pain and overall symptom relief, which improved in 34% of the postbiotic group versus 19% on placebo over 8 weeks. Side effects were similar to placebo. Postbiotics in infant formula did not change rates of diarrhea, colic or other digestive symptoms in a meta-analysis of nine trials. If your bowel habits change suddenly or persist, see a clinician rather than self-treating.
Can postbiotics help with weight loss or reduce belly fat?
The evidence is weak. In a 32-person pilot trial, pasteurized Akkermansia muciniphila improved insulin sensitivity and cholesterol over three months, but the 2.27 kg weight difference versus placebo was not statistically significant. A larger 2026 trial in 142 adults with metabolic syndrome found no difference in its primary insulin-sensitivity endpoint, Trunk fat fell only in an exploratory subgroup that started with low Akkermansia levels. No postbiotic has been shown to cause meaningful weight loss or belly-fat reduction.
Should I take a postbiotic or a probiotic if I'm constipated?
There is little to go on for postbiotics. Our PubMed searches in October 2026 found no randomized trial of a postbiotic designed around constipation. The main gut trial, in IBS, measured abdominal pain and overall symptom relief rather than stool frequency. Our guide to probiotics for constipation covers the live strains that have been tested. If constipation is new, severe or persistent, see a clinician first.
Do postbiotics or probiotics help with serotonin?
Not in any way shown in people for postbiotics. The ISAPP panel lists signaling through the nervous system as one proposed mechanism, but it remains a hypothesis. Our PubMed searches in October 2026 found no human trial showing that a postbiotic changes serotonin levels. Mood findings so far are limited to small exercise studies that reported less fatigue and better mood, without measuring serotonin.
When should you take postbiotics?
There is no evidence-based best time of day. Trials gave their postbiotic once daily, for example heat-inactivated B. bifidum MIMBb75 once a day for 8 weeks and heat-killed Lactobacillus pentosus b240 tablets once daily for 20 weeks. Because postbiotic cells are not alive, the timing questions that apply to live probiotics, such as surviving stomach acid, matter less. Follow the label of the specific product and the regimen used in its trial, if it has one.
Are heat-killed probiotics the same as postbiotics?
Heat-killed probiotics are one type of postbiotic, if the preparation has evidence of a health benefit. Earlier papers used terms such as paraprobiotics, ghostbiotics, non-viable probiotics and heat-inactivated probiotics for the same idea. The ISAPP panel folded these into one word, postbiotics, and widened it: heat is only one inactivation method, alongside high pressure, ultrasonication, radiation and drying, and the starting microbe does not have to be a recognized probiotic.
Can you take postbiotics with probiotics?
Many people already do without knowing it. Probiotic products and fermented foods often contain dead cells alongside live ones, though whether those dead cells contribute to the benefit has rarely been established. A combination product is only as good as the evidence for each named ingredient, so check each one separately.
References
- Salminen S, Collado MC, Endo A, et al.. The International Scientific Association of Probiotics and Prebiotics (ISAPP) consensus statement on the definition and scope of postbiotics. Nature Reviews Gastroenterology & Hepatology. 2021;18(9):649-667. doi:10.1038/s41575-021-00440-6 ↩
- Malagón-Rojas JN, Mantziari A, Salminen S, Szajewska H. Postbiotics for Preventing and Treating Common Infectious Diseases in Children: A Systematic Review. Nutrients. 2020;12(2):389. doi:10.3390/nu12020389 ↩
- Andresen V, Gschossmann J, Layer P. Heat-inactivated Bifidobacterium bifidum MIMBb75 (SYN-HI-001) in the treatment of irritable bowel syndrome: a multicentre, randomised, double-blind, placebo-controlled clinical trial. The Lancet Gastroenterology & Hepatology. 2020;5(7):658-666. doi:10.1016/s2468-1253(20)30056-x ↩
- Hill C, Guarner F, Reid G, et al.. The International Scientific Association for Probiotics and Prebiotics consensus statement on the scope and appropriate use of the term probiotic. Nature Reviews Gastroenterology & Hepatology. 2014;11(8):506-514. doi:10.1038/nrgastro.2014.66 ↩
- Gibson GR, Hutkins R, Sanders ME, et al.. 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. 2017;14(8):491-502. doi:10.1038/nrgastro.2017.75 ↩
- Vinderola G, Sanders ME, Salminen S. The Concept of Postbiotics. Foods. 2022;11(8):1077. doi:10.3390/foods11081077 ↩
- EFSA Panel on Nutrition, Novel Foods and Food Allergens (NDA), Turck D, Bohn T, et al.. Safety of pasteurised Akkermansia muciniphila as a novel food pursuant to Regulation (EU) 2015/2283. EFSA Journal. 2021;19(9). doi:10.2903/j.efsa.2021.6780 ↩
- Nocerino R, Paparo L, Terrin G, et al.. Cow's milk and rice fermented with Lactobacillus paracasei CBA L74 prevent infectious diseases in children: A randomized controlled trial. Clinical Nutrition. 2017;36(1):118-125. doi:10.1016/j.clnu.2015.12.004 ↩
- Szajewska H, Kołodziej M, Skórka A, Pieścik-Lech M. Infant Formulas With Postbiotics. Journal of Pediatric Gastroenterology and Nutrition. 2022;74(6):823-829. doi:10.1097/mpg.0000000000003441 ↩
- European Medicines Agency. Bacterial lysate medicines for respiratory conditions to be used only for prevention of recurrent infections. European Medicines Agency. 2019. Available at: https://www.ema.europa.eu/en/news/bacterial-lysate-medicines-respiratory-conditions-be-used-only-prevention-recurrent-infections ↩
- Marco ML, Sanders ME, Gänzle M, et al.. The International Scientific Association for Probiotics and Prebiotics (ISAPP) consensus statement on fermented foods. Nature Reviews Gastroenterology & Hepatology. 2021;18(3):196-208. doi:10.1038/s41575-020-00390-5 ↩
- Shinkai S, Toba M, Saito T, et al.. Immunoprotective effects of oral intake of heat-killed Lactobacillus pentosus strain b240 in elderly adults: a randomised, double-blind, placebo-controlled trial. British Journal of Nutrition. 2012;109(10):1856-1865. doi:10.1017/s0007114512003753 ↩
- Depommier C, Everard A, Druart C, et al.. Supplementation with Akkermansia muciniphila in overweight and obese human volunteers: a proof-of-concept exploratory study. Nature Medicine. 2019;25(7):1096-1103. doi:10.1038/s41591-019-0495-2 ↩
- Castro‐Rodriguez JA, Turi KN, Forno E. A critical analysis of the effect of OM-85 for the prevention of recurrent respiratory tract infections or wheezing/asthma from systematic reviews with meta-analysis. Pediatric Allergy and Immunology. 2024;35(7):e14186. doi:10.1111/pai.14186 ↩
- Suenaert P, Segers A, Rymenans L, et al.. Effect of pasteurized Akkermansia muciniphila MucT on insulin sensitivity, body composition, and GLP-1 production in subjects with metabolic syndrome: impact of low baseline gut Akkermansia levels. Gut Microbes. 2026;18(1):2690689. doi:10.1080/19490976.2026.2690689 ↩
- Warp PV, Bilik SM, Ferrari LM, Keri JE. Prebiotics, Probiotics, and Postbiotics for Acne Vulgaris: A Systematic Review. Dermatology and Therapy. 2026;16(3):1531-1550. doi:10.1007/s13555-026-01659-4 ↩
- Kerksick CM, Moon JM, Jäger R. It's Dead! Can Postbiotics Really Help Performance and Recovery? A Systematic Review. Nutrients. 2024;16(5):720. doi:10.3390/nu16050720 ↩
- Liang X, Li Y, Zhao Z, Ding R, Sun J, Chi C. Safety and efficacy of adding postbiotics in infant formula: a systematic review and meta-analysis. Pediatric Research. 2023;95(1):43-51. doi:10.1038/s41390-023-02813-w ↩
- Dinleyici EC, Indrio F, Szajewska H, et al.. Recommendations on the health outcomes of infant formula supplemented with biotics by the ESPGHAN Special Interest Group on Gut Microbiota and Modifications. Journal of Pediatric Gastroenterology and Nutrition. 2025;82(1):289-304. doi:10.1002/jpn3.70195 ↩