Also measured alongside: Gut immune signalling proteins (reported a benefit); Immune-regulating protein (galectin-1) (reported a benefit); Interferon beta levels (reported a benefit).
Every resultsupplement
Probiotics
Also known as Lactobacillus, Bifidobacterium, Saccharomyces boulardii
Live microorganisms, commonly Lactobacillus and Bifidobacterium strains, that colonise the gut and influence digestion and immune signalling via short-chain fatty acid production; effects are strain- and dose-specific.
Be careful if: certain health conditions, pregnant, breastfeeding, some medical situations
Ask first if you take: immunosuppressants
Suspect a side effect? Report it to the MHRA Yellow Card scheme ↗
2linked conditions
20linked studies
Evidence
What the research actually shows
We link to relevant studies and leave interpretation to you and your healthcare professional.
What studies found
The headline results, condition by condition
The large figures are what the studies reported for each thing they measured. Open a card for every result.
Colour keyReported a benefitNo clear benefitUnclearPossible harmAmber is for highlights, such as where the most research is. It never means a result was good.
Safety
Safety and considerations
What sources report about side effects, who should be careful, and medicines to ask about first.
Be careful if you…
| Applies to | What sources say | Sources |
|---|---|---|
| certain health conditions | If you have an existing health condition or a weakened immune system, talk to a doctor before taking any probiotic supplements (NHS). | Probiotics — NHS tests and treatments page, page last reviewed 24 November 2022 |
| pregnant | No pregnancy-specific information on the source checked (NHS probiotics page); ask a doctor or midwife before taking probiotic supplements. | Probiotics — NHS tests and treatments page, page last reviewed 24 November 2022 |
| breastfeeding | No breastfeeding-specific information on the source checked (NHS probiotics page); ask a doctor or midwife before taking probiotic supplements. | Probiotics — NHS tests and treatments page, page last reviewed 24 November 2022 |
| some medical situations | Probiotics are generally classed as food rather than medicine in the UK, so they do not go through the testing medicines do, and the bacteria stated on the label are not always guaranteed (NHS). | Probiotics — NHS tests and treatments page, page last reviewed 24 November 2022 |
Medicines to ask about
| Severity | Medicine | Sources |
|---|---|---|
| ask first | immunosuppressants — Live microorganisms: people with a weakened immune system should talk to a doctor before taking any probiotic supplement (NHS). | Probiotics — NHS tests and treatments page, page last reviewed 24 November 2022 |
Evidence analytics
Where the evidence is concentrated
Audited published research for Probiotics by condition. Drill into a pair page for the full breakdown.
Probiotics: findings by condition
What this means: Bars count reported findings, not treatment effectiveness or certainty.
One study may report several findings or appear in more than one pairing. Counts do not show the size of an effect. Comparable numerical estimates are not established for this summary.
View the full data table
| Compound and condition | Findings (count) | Studies (count) | Reported results (finding counts) | How sure? |
|---|---|---|---|---|
| Immune Support | 3 | 1 | Benefit: 3; no benefit: 0; harm: 0; unclear: 0; not recorded / unrecognised: 0 | Not formally graded |
Suggested uses (unproven)
Where people report using it and what trials suggest
- Strong evidenceAntibiotic-associated diarrhoea prevention (L. rhamnosus GG, S. boulardii)
- Moderate evidenceIBS symptom relief (specific strains: Bifidobacterium 35624 etc.)
- Strong evidenceNecrotising enterocolitis risk in preterm infants (in hospital)
Where the evidence is negative
Common claims the trials do not support
- General 'immunity/energy/wellbeing' claims not supported.
- Many retail products contain strains never tested for the buyer's condition.
- May delay gut microbiome reconstitution after antibiotics (2018 finding).
Live microorganisms with strain- and condition-specific evidence; benefit depends entirely on matching the right strain to the right condition.
Evidence grades reflect study quality and consistency, not marketing claims.
20studies referenced
17journals
2011–2025publication range
Ordered by strength of evidence, then result direction.
01Probiotic, prebiotic, synbiotic and fermented food supplementation in psychiatric disorders: A systematic review of clinical trialsRibera C, et al. · Neuroscience and biobehavioral reviews · 2024PMID 38280441 ↗02Probiotics fortify intestinal barrier function: a systematic review and meta-analysis of randomized trialsZheng Y, et al. · Frontiers in immunology · 2023PMID 37168869 ↗03The Efficacy and Safety of Probiotics for Allergic Rhinitis: A Systematic Review and Meta-AnalysisLuo C, et al. · Frontiers in immunology · 2022PMID 35663980 ↗04Exercise-induced stress behavior, gut-microbiota-brain axis and diet: a systematic review for athletesClark A, et al. · Journal of the International Society of Sports Nutrition · 2016PMID 27924137 ↗05The Effect of Probiotics on Health in Pregnancy and Infants: A Randomized, Double-Blind, Placebo-Controlled TrialBinda S, et al. · Nutrients · 2025PMID 40507094 ↗06Efficacy and safety of topical Streptococcus postbiotic emollient in adolescents and adults with mild-to-moderate atopic dermatitis: A randomized, double-blind, vehicle-controlled trialKim MS, et al. · Allergy · 2024PMID 38436460 ↗Show all 20 studies
07Bifidobacterium and Lactobacillus Probiotics and Gut Dysbiosis in Preterm Infants: The PRIMAL Randomized Clinical TrialVan Rossum T, et al. · JAMA pediatrics · 2024PMID 39102225 ↗08Effect of synbiotic supplementation on immune parameters and gut microbiota in healthy adults: a double-blind randomized controlled trialLi X, et al. · Gut microbes · 2023PMID 37614109 ↗09Modulating a prebiotic food source influences inflammation and immune-regulating gut microbes and metabolites: insights from the BE GONE trialZhang X, et al. · EBioMedicine · 2023PMID 38040541 ↗10Bifidobacteria-mediated immune system imprinting early in lifeHenrick BM, et al. · Cell · 2021PMID 34143954 ↗11The therapeutic efficacy of Bifidobacterium animalis subsp. lactis BB-12(®) in infant colic: A randomised, double blind, placebo-controlled trialNocerino R, et al. · Alimentary pharmacology & therapeutics · 2020PMID 31797399 ↗12Engineered probiotic ameliorates ulcerative colitis by restoring gut microbiota and redox homeostasisGuo P, et al. · Cell host & microbe · 2024PMID 39197456 ↗13[Small intestinal bacterial overgrowth (SIBO) - Therapy, nutrition, microbiome]Sellge G, et al. · Deutsche medizinische Wochenschrift (1946) · 2024PMID 39208859 ↗14Microbiota medicine: towards clinical revolutionGebrayel P, et al. · Journal of translational medicine · 2022PMID 35255932 ↗15Efficacy of an Irritable Bowel Syndrome Diet in the Treatment of Small Intestinal Bacterial Overgrowth: A Narrative ReviewWielgosz-Grochowska JP, et al. · Nutrients · 2022PMID 36014888 ↗16Probiotics, Prebiotics, and Synbiotics: Implications and Beneficial Effects against Irritable Bowel SyndromeSimon E, et al. · Nutrients · 2021PMID 34203002 ↗17Gut-brain Axis and migraine headache: a comprehensive reviewArzani M, et al. · The journal of headache and pain · 2020PMID 32054443 ↗18Mucus barrier, mucins and gut microbiota: the expected slimy partners?Paone P, et al. · Gut · 2020PMID 32917747 ↗19Prebiotics and Probiotics in Digestive HealthQuigley EMM · Clinical gastroenterology and hepatology : the official clinical practice journal of the American Gastroenterological Association · 2019PMID 30267869 ↗20Stress and the gut: pathophysiology, clinical consequences, diagnostic approach and treatment optionsKonturek PC, et al. · Journal of physiology and pharmacology : an official journal of the Polish Physiological Society · 2011PMID 22314561 ↗
Published research results
Reported results grouped by condition. Values and units are preserved as recorded; missing information is not estimated.
How to read this table
- Benefit
- What the trial saw happen: whether the measured outcome moved in the helpful direction in that one study (the tag on each row: “Benefit seen”, “No clear benefit”, “Possible harm” or “Unclear”). It is a study result — not advice, and not a promise it will work for you.
- Evidence
- Study design describes how research was conducted. It is not a formal certainty assessment.
- Effect size
- The result recorded in this summary. “Not reported” means the value is missing from the summary; it does not establish that the publication omitted it.
Reported direction, numerical results and study design are separate. Certainty has not been formally graded in this table.
Immune Support (3 outcomes)
| What was measured | Reported findings | Result and units | Reported sample and duration | Study / source |
|---|---|---|---|---|
| immunoregulatory galectin-1 | Galectin-1 was upregulated in Th2 and Th17 cells in infants supplemented with Bifidobacterium infantis EVC001 compared to those lacking bifidobacteria.Benefit seen | Not reported Recorded unit: Not reported | Sample (as reported): Not reported Follow-up: first months of life | Randomised trial · 2021 Study detailsBifidobacteria-mediated immune system imprinting early in life. Randomized Controlled Trial |
| interferon beta (IFN-beta) | Interferon beta was induced in breastfed infants given Bifidobacterium infantis EVC001 compared to those lacking bifidobacteria.Benefit seen | Not reported Recorded unit: Not reported | Sample (as reported): Not reported Follow-up: first months of life | Randomised trial · 2021 Study detailsBifidobacteria-mediated immune system imprinting early in life. Randomized Controlled Trial |
| intestinal T helper 2 (Th2) and Th17 cytokines | Th2 and Th17 cytokines were silenced in breastfed infants given Bifidobacterium infantis EVC001 compared to those lacking bifidobacteria.Benefit seen | Not reported Recorded unit: Not reported | Sample (as reported): Not reported Follow-up: first months of life | Randomised trial · 2021 Study detailsBifidobacteria-mediated immune system imprinting early in life. Randomized Controlled Trial |
Important: This page reflects observational, aggregate-only community reporting and independent published research. It is not medical advice, and it does not claim any compound treats, cures, or is effective for any condition. Always consult a qualified healthcare professional before starting, stopping, or changing any supplement or treatment.
Outcomes & conditions
Outcomes & conditions →Why people look into Probiotics — and what they report
Associated conditions and community-reported outcomes, wrapped together on one page. Aggregates appear only once enough reports arrive.
Important: This page reflects observational, aggregate-only community reporting and independent published research. It is not medical advice, and it does not claim any compound treats, cures, or is effective for any condition. Always consult a qualified healthcare professional before starting, stopping, or changing any supplement or treatment.
Availability
Where to get Probiotics (UK)
How this compound is sold in the UK, and where our readers typically find it.
Retailer search links — we may earn commission on purchases at no cost to you. Commission never affects our evidence ratings.