Quick answer
A synbiotic is a mix of live microbes and a substrate, usually a prebiotic fiber, that has been shown to give a health benefit as a mix. An 11-scientist panel of the International Scientific Association for Probiotics and Prebiotics (ISAPP) set that definition in 2020 and named two kinds, complementary and synergistic. It found that nearly all synbiotics tested or sold so far are complementary.
Key facts
- The word dates to 1995, when the paper that introduced prebiotics proposed combining them with probiotics as synbiotics. [Gibson and Roberfroid, Journal of Nutrition, 1995]
- A complementary synbiotic is a probiotic plus a prebiotic, each meeting its own definition at a dose that works alone; a synergistic synbiotic pairs a microbe with a substrate chosen for that microbe. [ISAPP consensus, Swanson et al., 2020]
- Nearly all synbiotics used in published trials or sold in stores are of the complementary kind, the 2020 panel wrote. [ISAPP consensus, Swanson et al., 2020]
- Commercial prebiotic preparations range from about 35% to 99% active substrate, the panel found, which is why it wants a synbiotic's substrate characterized. [ISAPP consensus, Swanson et al., 2020]
- In a 2018 trial with 114 adults randomized, two Bifidobacterium strains, each given with 5 g a day of galacto-oligosaccharides, showed no synergy: neither pair did better than its parts. [Krumbeck et al., Microbiome, 2018]
On this page
What is a synbiotic?
A mixture of live microbes and something microbes feed on, with a health benefit shown for the mixture itself, the test that sets it apart from a label that simply lists both. The 2020 ISAPP panel, convened in May 2019 and led by Kelly Swanson, wrote the definition in these words:12
"a mixture comprising live microorganisms and substrate(s) selectively utilized by host microorganisms that confers a health benefit on the host"
ISAPP consensus statement on synbiotics, Swanson et al., Nature Reviews Gastroenterology and Hepatology, 2020
Two parts of that sentence do the work. "Host microorganisms" covers both the microbes already living in you and the ones the product adds, so the substrate can feed either. And the benefit has to be confirmed in the target host, which the panel says could be people, companion animals, farm animals, or a subgroup such as one age group.1 The panel also says a synbiotic can work outside the gut, and ISAPP's own summary gives the skin as an example.2
US health agencies use looser wording. NCCIH, part of NIH, answers the question in one line, describing synbiotics simply as products that pair probiotics with prebiotics.5 The ISAPP definition adds the test that the mixture itself must be shown to work.
Where does the word synbiotic come from?
From the same 1995 paper that introduced prebiotics. Glenn Gibson and Marcel Roberfroid, writing in the Journal of Nutrition, proposed that by combining the rationale of probiotics and prebiotics, "the concept of synbiotics" could describe some colonic foods. The 2020 panel says the term was built from the Greek prefix "syn", meaning together, and "biotic", meaning pertaining to life.41
The panel adds a warning about the prefix: "syn" means together, not synergy, and "'Symbiotic' is not a synonym of synbiotic and is incorrect in this context." In biology, symbiotic describes two organisms living together over the long term.1 The idea of two kinds, complementary and synergistic, was proposed in 2011, ISAPP says, and nearly 200 clinical studies of synbiotics appeared in the decade before the 2020 definition; by the panel's PubMed search, 269 papers used the term in 2019 alone.21
Complementary vs synergistic synbiotic: what does each one have to prove?
What each part has to prove on its own. In a complementary synbiotic, an established probiotic and an established prebiotic are combined, each at a dose shown to work by itself, and the prebiotic is aimed at the microbes already in your gut. In a synergistic synbiotic, neither part needs to qualify alone; the substrate is chosen to feed the microbe given with it, and a single trial has to show both that and the benefit.1
The two kinds of synbiotic, by what the 2020 panel requires
| Question | Complementary synbiotic | Synergistic synbiotic |
|---|---|---|
| The live microbe | Must already meet the probiotic definition | Need not be a probiotic on its own; chosen for the benefit it gives with the substrate |
| The substrate | Must already meet the prebiotic definition | Need not be a prebiotic on its own; chosen to be used by the microbe given with it |
| Which microbes the substrate is for | The resident microbes in your gut | Mainly the microbe in the product |
| Doses | Each part at a dose shown to work alone | Enough for the microbe to use the substrate and give the benefit |
| Trial the panel asks for | The synbiotic against an inert control, two arms | The microbe, the substrate, the two together, and a control |
| What the trial must show | The synbiotic beats the control | The pair does better than the estimated effects of each part, and the microbe uses the substrate, in the same study |
| How common | Nearly all synbiotics in trials or on sale | Rare; the panel calls them experimentally challenging to design and prove |
Source: ISAPP consensus statement on synbiotics, Swanson et al., 2020, Box 1, Table 2 and the text on synergistic designs, read on Oct 22, 2026. Effective doses must still be present at the end of shelf life, the panel's Table 2 adds. An example of a four-arm test, and what it found, is in do I need a prebiotic with my probiotic?
The panel considered making every synbiotic synergistic, then decided against it: it noted that no such substance existed yet, which showed how hard such evidence is to produce, and a usable definition mattered more than a hypothetical one.1
Is a synbiotic better than a probiotic alone?
Not by default, and the panel did not require it to be. It wrote that the ideal synbiotic would beat the sum of its parts, but because that is hard to show in a trial, it asked only for a measurable, confirmed health benefit. It also required that benefit to be confirmed even when proven parts are combined, because a pairing could in theory cancel out some of what each part does.1
The clearest test so far comes from one group. In rats, adding galacto-oligosaccharides (GOS) raised a selected Bifidobacterium adolescentis strain, IVS-1, nearly 100-fold in the lower gut, by about 2 logs, compared with the strain alone.6 In people, the same team randomized 114 adults, selected for a condition this page does not cover, to six arms for 3 weeks, with 5 g a day of GOS. IVS-1 alone raised total bifidobacteria about as much as GOS did, but given together with GOS, both strains tested showed only a trend toward higher numbers that was not significant, and no synergy on the outcomes measured.7 Two of its authors co-own a company that develops synbiotic products with that strain, and one was on ISAPP's board at the time.7
An ISAPP summary of a 2021 webinar with its board members adds that some measures linked to health, such as more short-chain fatty acids in stool or a change in microbiota makeup, may not be enough on their own to show a health benefit.8
Is every product with a prebiotic and a probiotic a synbiotic?
No. Under the 2020 definition, a product earns the word only when its own combination has been tested and shown to give a health benefit; containing both is not enough. ISAPP's synbiotics page puts it simply: in either kind, evidence must show that the combination of the two ingredients confers a health benefit in a human or other host population.31
Reading the five panel lines of a combination product, from strain to prebiotic amount, is done line by line in prebiotic and probiotic supplements: what to check on a combo label, and the four ISAPP definitions sit side by side in prebiotic vs probiotic.
What should a synbiotic label show?
Enough to trace the microbe, the substrate and the study of the pair. The panel asks that a synbiotic's microbe have a publicly available genome sequence, be checked for genes of safety concern and be deposited in an international culture collection, that the substrate be characterized, and that the dose shown to work still be present at the end of shelf life. It also says claims must match what the trial tested.1
Label words and what they should stand for
| If the label says | Under the 2020 definition | What to look for |
|---|---|---|
| "Synbiotic" | Allowed when the criteria for either kind are met | A named study of that exact combination, with its dose |
| "Complementary synbiotic" | An established probiotic plus an established prebiotic, tested together against an inert control | The strain designation, the prebiotic by name and amount, and the trial |
| "Synergistic synbiotic" | A substrate shown, in the same trial as the benefit, to be used by the microbe it comes with | A four-arm trial: microbe, substrate, both, control |
| "Symbiotic" | Not a synonym; the panel calls it incorrect in this context | Read it as the wrong word for this, then check the strain, the substrate and the study |
| "With prebiotics" or both listed, no claim | A product that contains both; the word synbiotic needs evidence for the pair | The five panel lines covered on our combo label page |
Source: ISAPP consensus statement on synbiotics, Swanson et al., 2020, including Table 2's note on label use, read on Oct 22, 2026. The "what to look for" column is ours, drawn from the panel's criteria.
Two numbers explain why. The panel found that commercial prebiotic preparations range from about 35% to 99% active substrate, so the same weight of "prebiotic" can hold different amounts of the active substance. And microbe survival depends on the product: liquid products may keep their live count for as little as 1 to 2 weeks, freeze-dried or encapsulated ones for as long as 2 years.1
"results should not be extrapolated to health conditions, populations or synbiotics that have not been studied"
ISAPP consensus statement on synbiotics, Swanson et al., 2020
Are synbiotics regulated?
Not as their own category. The 2020 panel notes that the term synbiotic may not appear in any government guideline or regulation, and that the word "does not stipulate a regulatory category": a synbiotic sold as a food, a supplement or a drug has to meet the rules for that category. It hopes its definition will help regulators judge products labeled as synbiotics.1
It also expects change abroad. Because the European Union counts "probiotic" or "prebiotic" on a food label as an implied health claim that needs approval, the panel expected the EU might take the same view of "synbiotic", since the word also requires evidence of a health benefit.1 The panel was convened by ISAPP, a nonprofit funded by companies that sell probiotics and prebiotics and guided by an independent, volunteer academic board, as the paper discloses.1
Where Physician's Choice fits
Physician's Choice, which publishes this site, sells Prebiotic Probiotic, a label that lists both parts: inulin from chicory at 250 mg, and a 26 mg probiotic blend with 10 billion CFU from 3 Lactobacillus species, with no strain codes.9
Listing both is not the same as being a synbiotic. The 2020 definition needs a study of that exact combination, none is cited here, and neither the label nor the product page read on Oct 22, 2026 uses the word.
See the label on physicianschoice.comTalk to a professional if
- You are choosing a synbiotic for a specific health reason; the panel says results should not be carried over to conditions or people that were not studied1
If you are pregnant or breastfeeding, are seriously ill, or have a weakened immune system, consult your healthcare provider before taking a probiotic or any other dietary supplement.
The panel's caution comes first; the closing line is Physician's Choice wording, as written.
Synbiotics, in two sentences
A synbiotic is live microbes plus a substrate that has been shown, as a mixture, to give a health benefit, and it comes in a complementary kind, two proven parts tested together, and a rarer synergistic kind built and tested as a pair. A label that simply lists a prebiotic and a probiotic does not meet that test on its own, and the one direct human test of synergy summarized here found none.
How this page was made
| The question | "What is a synbiotic?" and its neighbors, synbiotic supplements, synbiotic probiotics and synbiotic vs probiotic, as people ask search and AI answer engines. |
|---|---|
| Sources | Eight public sources, all opened and read on Oct 22, 2026: the 2020 ISAPP consensus paper in full, three ISAPP web pages, the 1995 paper that coined the word, NCCIH, and two trials of one strain with GOS. |
| Tables | Built from the consensus paper's Box 1, Tables 2 and 3 and its text; the "what to look for" column is our reading of those criteria. |
| Label facts | One line, from the Prebiotic Probiotic panel, read against Physician's Choice's label image on Oct 22, 2026. |
| Shopper words | Of 1,145 public Reddit posts from 250 communities, Sep 12 to Oct 12, 2026, one used the word, and it was spelled "symbiotic". |
| Physician's Choice wording | The professional section quotes its line on pregnancy and immunity, as written. |
Synbiotic questions
What is the difference between a synbiotic and a probiotic?
A probiotic is live microbes with a shown health benefit; a synbiotic adds a substrate, usually a prebiotic fiber, and needs the benefit shown for the mixture. Under ISAPP's 2020 definition, a complementary synbiotic is a proven probiotic plus a proven prebiotic, tested together against a control.
Is synbiotic the same as symbiotic?
No. The 2020 ISAPP panel says "symbiotic" is not a synonym of synbiotic and is incorrect in this context. Symbiotic describes two organisms living together over the long term. Synbiotic comes from "syn", together, and "biotic", pertaining to life, and names a product category.
Do synbiotics work?
It depends on the exact mix. The 2020 panel asks each synbiotic to show a confirmed health benefit in its target group, and says results should not be carried over to other conditions, people or products. In one 2018 human trial, two Bifidobacterium strains, each with GOS, showed no synergy.
Can foods be synbiotics?
The definition allows it: the 2020 panel says synbiotics can be foods, supplements, drugs or other product types. The test is the same for all of them, though. ISAPP's synbiotics page says evidence must show that the combination of the two ingredients confers a health benefit.
Who defined synbiotics?
Glenn Gibson and Marcel Roberfroid proposed the concept in 1995. The current definition comes from an 11-scientist ISAPP panel that met in May 2019, was led by Kelly Swanson, and published its consensus statement in Nature Reviews Gastroenterology and Hepatology in 2020.
Sources
- Swanson KS, Gibson GR, Hutkins R, et al. The International Scientific Association for Probiotics and Prebiotics (ISAPP) consensus statement on the definition and scope of synbiotics. Nature Reviews Gastroenterology and Hepatology. 2020;17(11):687-701. pmc.ncbi.nlm.nih.gov
- ISAPP. New synbiotic definition lays the groundwork for continued scientific progress. By Karen Scott, Mary Ellen Sanders, Kelly Swanson, Glenn Gibson and Bob Hutkins. Published Aug 21, 2020. isappscience.org
- ISAPP. Synbiotics (consumer resource). Updated Sep 25, 2025. isappscience.org
- Gibson GR, Roberfroid MB. Dietary modulation of the human colonic microbiota: introducing the concept of prebiotics. Journal of Nutrition. 1995;125(6):1401-12. pubmed.ncbi.nlm.nih.gov
- NCCIH (National Institutes of Health). Probiotics: usefulness and safety. Last updated Aug 2019. nccih.nih.gov
- Krumbeck JA, Maldonado-Gomez MX, Martínez I, et al. In vivo selection to identify bacterial strains with enhanced ecological performance in synbiotic applications. Applied and Environmental Microbiology. 2015;81(7):2455-65. pubmed.ncbi.nlm.nih.gov
- Krumbeck JA, Rasmussen HE, Hutkins RW, et al. Probiotic Bifidobacterium strains and galactooligosaccharides improve intestinal barrier function in obese adults but show no synergism when used together as synbiotics. Microbiome. 2018;6(1):121. pmc.ncbi.nlm.nih.gov
- ISAPP. Follow up from ISAPP webinar: probiotics, prebiotics, synbiotics, postbiotics and fermented foods, how to implement ISAPP consensus definitions. By Mary Ellen Sanders, PhD. Published Jun 7, 2021. isappscience.org
- Physician's Choice Supplement Facts panel for Prebiotic Probiotic (label 3.4.0), read against Physician's Choice's own label image on Oct 22, 2026, and the product page on physicianschoice.com. physicianschoice.com