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Probiotics
Lactobacillus and Bifidobacterium species
TL;DR
Probiotic effects are strain-specific, not generic. Particular strains have good evidence for antibiotic-associated diarrhoea, acute infectious diarrhoea in children and some IBS symptoms. Products that list only genus and species, without a strain code, cannot be matched to any trial.
Ideal For
- Anyone starting a course of antibiotics, particularly broad-spectrum
- Children with acute gastroenteritis
- People with IBS willing to trial a specific strain for four weeks
- Travellers at risk of travellers diarrhoea
- Patients with pouchitis after colectomy
- People with recurrent C. difficile risk factors
Avoid If
- Severe immunocompromise, including neutropenia and transplant recipients
- Central venous catheter in situ — case reports of fungaemia with S. boulardii
- Acute pancreatitis, where a trial showed increased mortality
- Critically ill patients in intensive care, unless specifically directed
- Short bowel syndrome or a damaged intestinal barrier, without specialist advice
Frequently Asked Questions
Overview
Probiotics are the clearest example in the supplement world of a category being marketed as if it were a single product. The World Health Organization definition — live microorganisms which, when administered in adequate amounts, confer a health benefit — is deliberately conditional, and the condition matters. Benefits are established for particular strains at particular doses for particular indications. Lactobacillus rhamnosus GG has strong evidence for paediatric acute gastroenteritis; that tells you nothing about a different Lactobacillus in a different product.
This is why the strain code is not marketing pedantry. A label reading Lactobacillus rhamnosus is a species. Lactobacillus rhamnosus GG (ATCC 53103) is a strain, and it is strains that were studied. If a product does not name strains, no published trial applies to it.
Where the evidence is strongest: prevention of antibiotic-associated diarrhoea, where meta-analyses of Saccharomyces boulardii and L. rhamnosus GG show meaningful risk reduction; reduction of Clostridioides difficile infection risk when started early alongside antibiotics; shortening of acute infectious diarrhoea in children by roughly a day; and improvement in global IBS symptoms with certain multi-strain formulations, though effect sizes are modest and inconsistent between products.
Where the evidence is weak or absent: general gut health in asymptomatic people, immunity claims beyond modest reductions in respiratory infection duration, weight loss, and mood. The microbiome-and-mood literature is genuinely interesting and genuinely preliminary.
An honest framing: probiotics are transient. Most strains do not colonise; they pass through, exerting effects while present and disappearing within one to two weeks of stopping. That makes them a treatment to be taken continuously for a purpose, not a one-off reset.
How It Works
- Competitive exclusion — occupying binding sites and consuming substrate that pathogens would otherwise use
- Production of short-chain fatty acids, lowering luminal pH and feeding colonocytes
- Strengthening of the intestinal barrier through increased tight-junction protein expression
- Modulation of gut-associated lymphoid tissue and cytokine signalling
- Production of bacteriocins with direct antimicrobial activity
- Bile salt hydrolase activity, which underlies modest cholesterol effects in some strains
- Saccharomyces boulardii additionally degrades C. difficile toxin A and B receptors — it is a yeast, so antibiotics do not kill it
Quick Facts
- Live beneficial bacteria that support gut health
- Multiple strains provide different health benefits
- Support immune system and digestive function
- May influence mood through gut-brain connection
- Quality and strain specificity are crucial
Benefits & Outcomes
Fungal Infection Resistance
Strain-specific and adjunctive. Generic probiotics are unlikely to help.
Bloating Reduction
Certain strains reduce bloating, but results are strain-specific.
Candida Control
Lactobacillus-based probiotics modestly reduce recurrence of vulvovaginal candidiasis but do not replace antifungal therapy.
Constipation Relief
Specific Bifidobacterium strains modestly increase stool frequency, adding roughly one bowel movement per week.
Weight Loss Support
Probiotic weight effects are strain-specific, small and inconsistently replicated.
Post-Illness Recovery
Specific strains reduce antibiotic-associated diarrhoea, which is the clearest recovery use case.
Respiratory Tract Protection
Probiotics modestly reduce the number and duration of upper respiratory infections.
SIBO Prevention
Probiotic evidence in SIBO is genuinely conflicted — some strains help symptoms, others may worsen bloating.
T-Cell Function Enhancement
Probiotics modulate mucosal immunity with strain-specific and inconsistent T-cell effects.
Bacterial Infection Prevention
Probiotics reduce antibiotic-associated diarrhoea and C. difficile infection.
Intestinal Motility
Some probiotic strains speed transit modestly, but effects are strain-specific rather than a class benefit.
Mucosal Immunity
Meta-analyses show probiotic use reduces respiratory infection incidence and duration modestly, and improves antibiotic-associated gut barrier disruption.
Pancreatic Enzyme Support
Probiotics may help small intestinal bacterial overgrowth that accompanies pancreatic disease, but do not replace enzymes.
Diarrhea Prevention
Lactobacillus rhamnosus GG is well evidenced for preventing antibiotic-associated and paediatric infectious diarrhoea.
Cold Prevention
Probiotics modestly reduce upper respiratory infection incidence and duration in meta-analyses.
Microbiome Diversity Enhancement
Probiotics add transient beneficial strains and help restore disrupted communities, but rarely produce lasting increases in native diversity.
Gut-Brain Axis Support
Strain-specific benefits for gut symptoms, with smaller and less consistent mood effects.
Gut Microbiome Support
Probiotics transiently increase microbial diversity and functional output while being taken; durable colonisation generally does not occur.
Immune Function
Probiotics modestly reduce the incidence and duration of upper respiratory tract infections in meta-analysis. Effects are strain-specific and small, so results from one product do not transfer to another.
Gut Barrier Integrity
Certain strains reduce measured intestinal permeability in specific clinical settings, but barrier repair in general populations is largely unvalidated.
Mood Stabilization
Trials of probiotics for mood report small improvements in depressive symptoms, mainly in people with existing symptoms rather than healthy volunteers. The gut-brain literature is promising but early.
Health Concerns Addressed
H. Pylori Infection
Probiotics do not eradicate H. pylori alone, but taken alongside antibiotic therapy they cut side effects like diarrhoea, improve course completion, and modestly raise eradication rates. This is one of the best-evidenced probiotic uses — as an adjunct to, never a replacement for, the antibiotic regimen.
Abdominal Cramping
Meta-analyses show a statistically significant but small global benefit; the field cannot yet say which strain helps which patient, and some people worsen (especially with SIBO-pattern bloating).
Ulcerative Colitis
A reasonable add-on to mesalazine in mild to moderate disease, and genuinely effective for pouchitis prevention. Not a replacement for maintenance therapy.
Candida Overgrowth
Legitimate adjunct for preventing recurrent vaginal yeast infections; not a treatment for active infection, and irrelevant to the overgrowth myth.
Diverticulitis
Plausible mechanism and some positive small trials in symptomatic uncomplicated disease, but too inconsistent to recommend. Fiber and lifestyle carry the real evidence.
Urinary Tract Infection
A reasonable option for recurrent infection in women, using the specific strains studied. Useless for treating an active infection, which needs antibiotics.
Inflammatory Bowel Disease
Strong evidence in pouchitis and modest support in ulcerative colitis; essentially no benefit demonstrated in Crohn's disease.
Sore Throat
Sensible for recurrent throat infections using oral-colonizing strains; mostly irrelevant for the drip/reflux causes of chronic sore throat.
Tongue Coating
Probiotics are marketed for coated tongue on the theory of rebalancing the oral microbiome, but there are no meaningful trials for this use. Tongue cleaning, hydration, and treating dry mouth or thrush address the actual causes.
Lactose Intolerance
Modest, strain-specific benefit; lactase supplements and dietary adjustment work better.
Food Sensitivities
Worth a time-limited trial of a studied strain; not a fix for a genuine allergy or coeliac disease.
Bad Breath
Early, encouraging data for oral-specific strains as an add-on; gut probiotics in capsules are a different, untested bet for this indication.
Skin Rashes
Probiotics have modest evidence for eczema in children but little for rashes in general — and most rashes need a diagnosis, not a supplement.
Bloating & Gas
Specific strains, notably Bifidobacterium infantis 35624 and multi-strain Lactobacillus/Bifidobacterium blends, reduce bloating and distension in IBS-type presentations.
Frequent Diarrhea
This is the strongest indication in the probiotic field: Saccharomyces boulardii and Lactobacillus rhamnosus GG substantially reduce antibiotic-associated and infectious diarrhoea. Timing is everything — start within 48 hours of the first antibiotic dose.
Stomach Pain
Some specific strains modestly reduce functional abdominal pain, but benefits do not generalise across products and effect sizes are small.
Digestive Issues
Probiotics have genuine, strain-specific evidence for several digestive complaints — notably IBS symptoms and antibiotic-associated diarrhea — though results vary widely by product and condition.
IBS (Irritable Bowel Syndrome)
Specific probiotic strains improve global IBS symptoms and bloating, with Bifidobacterium infantis 35624 the best-studied single strain. Effects are modest and strain-dependent — a product that does not name its strains cannot be matched to any trial.
Food Allergies
Modest prevention signal in high-risk infants; no treatment effect for established allergy.
Eczema (Atopic Dermatitis)
Probiotics show the clearest benefit for eczema prevention when given perinatally, with weaker and less consistent effects when used to treat established disease. Strain choice matters and results do not generalise across products.
Chronic Constipation
Bifidobacterium lactis strains modestly speed colonic transit and increase stool frequency by roughly one bowel movement per week in meta-analysis. Real, but small — fibre, fluid and movement do more, and probiotics are best used alongside them.
Frequent Infections
Probiotics produce small reductions in the duration and, less consistently, the frequency of respiratory infections — roughly a day or two shorter per episode in meta-analysis. Real but modest, and nowhere near what immune-boosting marketing implies.
Hashimoto's Thyroiditis
Probiotics have not been shown to change thyroid antibodies or hormone levels in Hashimotos thyroiditis.
Supporting Research107 studies
Probiotics for the prevention of antibiotic-associated diarrhea in adults: a meta-analysis of randomized placebo-controlled trials
Liao W, Chen C, Wen T +1 more
Probiotics reduced the incidence of antibiotic-associated diarrhoea by roughly 40 percent, with benefit strongest when started early in the antibiotic course.
Preventing food allergy in infancy and childhood: Systematic review of randomised controlled trials
Neither maternal nor infant supplementation with probiotics, prebiotics, vitamin D or fish oil consistently prevented allergic disease or wheeze.
Probiotics for digestive and immune health
Kechagia, M., Basoulis, D.
Probiotics significantly reduced antibiotic-associated diarrhea by 42% (RR 0.58) Reduced incidence of C. difficile infection by 64% (RR 0.36) Decreased duration of acute diarrhea by 25 hours on average Improved IBS symptoms with specific strains (Bifidobacterium, Lactobacillus) Reduced upper respiratory tract infections by 30% Strain-specific effects observed - not all probiotics equally effective Higher doses (≥10 billion CFU) more effective than lower doses Multi-strain formulations often supe
Health Benefits of Probiotics: A Review
Kechagia M, Basoulis D, Konstantopoulou S +4 more
Reviewed evidence supports probiotics for antibiotic-associated and infectious diarrhoea, some benefit in irritable bowel syndrome symptoms, and modulation of mucosal immunity through competitive exclusion of pathogens, barrier reinforcement and cytokine modulation. Effects are strain-specific and dose-dependent; benefits shown for one strain cannot be assumed for others.
Probiotics for the management of irritable bowel syndrome: a systematic review and three-level meta-analysis
Xie P, Luo M, Deng X +2 more
Probiotics produced small significant reductions in global IBS symptom severity and abdominal pain, with effects varying widely by strain.
Probiotics for the Prevention of Antibiotic-Associated Diarrhea in Outpatients: A Systematic Review and Meta-Analysis
Blaabjerg S, Artzi DM, Aabenhus R
Probiotics including S. boulardii reduced antibiotic-associated diarrhoea in outpatients, with a number needed to treat around 13.
Regulation of abdominal adiposity by probiotics (Lactobacillus gasseri SBT2055) in adults with obese tendencies in a randomized controlled trial
Kadooka Y, Sato M, Imaizumi K +6 more
Visceral and subcutaneous fat areas decreased significantly with LG2055 compared with control, alongside reductions in body weight and waist circumference.
Multicenter, Randomized, Double-Blind Trial of Probiotics for Acute Gastroenteritis in Children
Freedman SB, Williamson-Urquhart S, Farion KJ
A five-day probiotic course did not prevent moderate-to-severe gastroenteritis within 14 days versus placebo.
Probiotics in primary prevention of atopic disease: a randomised placebo-controlled trial
Kalliomaki M, Salminen S, Arvilommi H
Perinatal LGG halved the frequency of atopic eczema in at-risk children at age two (23% vs 46%).
Probiotic supplementation and digestive health: A comprehensive review
Garcia, M., Kumar, S., Nielsen, J.
Probiotics significantly reduced antibiotic-associated diarrhea by 42% (RR 0.58) Reduced incidence of C. difficile infection by 64% (RR 0.36) Decreased duration of acute diarrhea by 25 hours on average Improved IBS symptoms with specific strains (Bifidobacterium, Lactobacillus) Reduced upper respiratory tract infections by 30% Strain-specific effects observed - not all probiotics equally effective Higher doses (≥10 billion CFU) more effective than lower doses Multi-strain formulations often supe
Probiotics for the prevention of Clostridium difficile-associated diarrhea in adults and children
Goldenberg JZ, Yap C, Lytvyn L +4 more
Moderate certainty evidence suggests that probiotics are effective for preventing Clostridium difficile-associated diarrhea.
The effect of probiotic supplementation on perceived stress and bowel function in healthy young adults: evidence from a randomized controlled trial in Makkah
Noorwali E, et al.
A 30-day LGG course may reduce perceived stress-particularly in males-with a trend level effect observed in females without affecting bowel habits.
The impact of probiotics on Helicobacter pylori eradication with bismuth quadruple therapy: A systematic review and meta-analysis.
Liu YH, Zhang J, Li DH +1 more
PBQT significantly improved H. pylori eradication rates compared to BQT alone (pooled odds ratio [OR] = 1.49, 95% confidence interval [CI] 1.20-1.85; P = 0.0004), with low heterogeneity (I² = 0%).
Efficacy of Probiotics for Irritable Bowel Syndrome: A Systematic Review and Network Meta-Analysis
Zhang T, Zhang C, Zhang J +2 more
B.coagulans exhibited the highest probability to be the optimal probiotic specie in improving IBS symptom relief rate, as well as global symptom, abdominal pain, bloating, and straining scores.
Effects of selected dietary supplements on migraine prophylaxis: A systematic review and dose-response meta-analysis of randomized controlled trials
Talandashti MK, Shahinfar H, Delgarm P +1 more
Magnesium supplementation reduced migraine attacks (mean difference (MD) = -2.51), severity (MD = -0.88), and the monthly migraine days (MD = -1.66) compared with the control group.
Probiotics and secretory IgA in mucosal immunity: a systematic review and meta-analysis of randomized trials
Zhang H, Yeh C, Jin Z +3 more
Probiotics significantly increased secretory IgA concentrations and reduced infection incidence
Meta-analysis of randomized controlled trials of the effects of probiotics on functional constipation in adults
Zhang C
Consumption of probiotics, in particular, multispecies probiotics, may substantially reduce the GTT, increase the stool frequency, and improve the stool consistency.
Probiotics for Preventing and Treating Small Intestinal Bacterial Overgrowth: A Meta-Analysis and Systematic Review of Current Evidence
Zhong C, Qu C, Wang B +1 more
The probiotics group showed a significantly higher SIBO decontamination rate than the
Role of probiotics in chronic rhinosinusitis: a systematic review of randomised, controlled trials
Fong P, Lim K, Gnanam A +1 more
Lower sinusitis relapse risks during treatment (risk ratio = 0.49; p = 0.019) and 8 months post-treatment (risk ratio = 0.56, p = 0.013) were observed.
The use of probiotics and prebiotics can enable the ingestion of dairy products by lactose intolerant individuals
Oliveira LS, et al
B. bifidum 900791 did not significantly improve LI symptoms, and only Limosilactobacillus reuteri DSM 17938 showed significant improvement in symptoms and in reduction of expired hydrogen.
Probiotic supplementation decreases intestinal transit time: meta-analysis of randomized controlled trials
Miller LE, Ouwehand AC
Probiotics reduced whole gut transit time by approximately 12 hours versus control
Effectiveness of Prophylactic Oral and/or Vaginal Probiotic Supplementation in the Prevention of Recurrent Urinary Tract Infections
Probiotic prophylaxis did not significantly reduce recurrent urinary tract infections versus placebo.
Efficacy of probiotic supplementation in the treatment of psoriasis - a systematic review and meta-analysis
Wei K, Liao X, Yang T +6 more
The Psoriasis Area and Severity Index (SMD = -1.40, 95% Cl = -2.63 to -0.17, p < 0.00001) and Dermatology Life Quality Index (SMD = -0.92, 95% Cl = -1.86 to 0.01, p < 0.00001). Score decreased after probiotic supplementation.
Probiotics for vulvovaginal candidiasis in non-pregnant women
Xie HY, Feng D, Wei DM
Probiotics as adjuncts to antifungals may improve short-term cure and reduce one-month relapse of candidiasis.
Probiotics for induction of remission in Crohn's disease
Limketkai BN, Akobeng AK, Gordon M
The effects of probiotics on induction of remission in Crohn's disease are uncertain; the evidence is of very low certainty.
Probiotics for preventing acute otitis media in children
Scott AM, Clark J, Julien B +5 more
Probiotics may reduce the proportion of children experiencing acute otitis media.
Probiotics for the treatment of allergic rhinitis: a systematic review and meta-analysis
Zajac AE, Adams AS, Turner JH
Probiotics improved allergic rhinitis quality-of-life scores in the majority of included trials.
Effectiveness of the probiotic Streptococcus salivarius K12 for the treatment and/or prevention of sore throat: a systematic review
Wilcox CR, Stuart B, Leaver H +2 more
All were deemed to be of poor quality using the Cochrane risk-of-bias assessment.
The efficacy and safety of oral microecological agents as add-on therapy for atopic dermatitis: A systematic review and meta-analysis of randomized clinical trials
Xue P, et al.
However, adverse events, pruritus scores, quality of life, and frequency of TCS use showed no significant difference in this meta-analysis study (p > 0.05).
Probiotics for autism spectrum disorder: An updated systematic review and meta-analysis of effects on symptoms
Soleimanpour S, Abavisani M, Khoshrou A +1 more
Alterations in the gut microbiota may correlate with the severity of ASD symptoms.
Probiotic Supplementation and Its Impact on Atopic Dermatitis and Related Conditions in Infants and Children: An Umbrella Review of Systematic Reviews with Meta-Analyses
Rafiei Z
Our research suggests that probiotics could play a beneficial role in managing AD and eczema.
Randomized Controlled Trial of Probiotic PS128 in Children with Tourette Syndrome
Lactobacillus plantarum PS128 did not significantly improve tic severity scores in children with Tourette syndrome.
The efficacy and safety of probiotics in patients with irritable bowel syndrome: Evidence based on 35 randomized controlled trials
Niu HL, Xiao JY
Randomized controlled trials (RCTs) involving adults with IBS that compared probiotics to placebo or no therapy were eligible for the analysis.
Lacticaseibacillus rhamnosus HA-114 improves eating behaviors and mood-related factors in adults with overweight during weight loss
Choi BS, Brunelle L, Pilon G +2 more
Although probiotic supplementation did not potentiate the reduction in body weight or fat mass
The positive benefit of Lactobacillus paracasei NCC2461 ST11 in healthy volunteers with moderate to severe dandruff
Reygagne P
Regular intake of ST11 over 56 days is safe and reduces significantly the severity of signs and symptoms of moderate to severe dandruff.
Efficacy of probiotics: clinical and microbial parameters of halitosis
Two studies reported a significant reduction in ORG between probiotic and placebo groups, and two studies on the basis of total VSC levels.
Effects of probiotics, prebiotics, and synbiotics on gut microbiota in older adults: a systematic review and meta-analysis of randomized controlled trials
Zhuang K, Luo H, Zeng M
Probiotic supplementation enhanced microbial diversity (Shannon index: SMD = 0.76).
The anxiolytic effect of probiotics: A systematic review and meta-analysis of the clinical and preclinical literature
Reis DJ
While preclinical (animal) studies suggest that probiotics may help reduce anxiety, such findings have not yet translated to clinical research in humans.
Administration of a probiotic with peanut oral immunotherapy: a randomized trial
Tang ML, Ponsonby AL, Orsini F +4 more
Lactobacillus rhamnosus combined with oral immunotherapy was associated with sustained unresponsiveness to peanut.
Safety and Effectiveness of Oral Nutraceuticals for Treating Acne: A Systematic Review
Shields A, Ly S, Wafae B +7 more
This systematic review suggests a possible role for nutraceutical supplements in the treatment of acne.
Effect of Lactobacillus plantarum LMT1-48 on Body Fat in Overweight Subjects: A Randomized, Double-Blind, Placebo-Controlled Trial
Sohn M, Jung H, Lee WS +1 more
A similar pattern was found in abdominal VFA between the two groups (P=0.041).
Efficacy of Synbiotics to Reduce Symptoms and Rectal Inflammatory Response in Acute Radiation Proctitis: A Randomized, Double-Blind, Placebo-Controlled Pilot Trial
Nascimento M
Synbiotics reduce proctitis symptoms and improve quality of life by preventing rectal inflammation during radiotherapy for prostate cancer.
Investigating the effects of probiotics during the menopause transition: A systematic review & meta-analysis
Probiotics showed limited and inconsistent effects on symptoms during the menopause transition.
The effect of probiotics on halitosis: a systematic review and meta-analysis
Yoo JI, Shin IS, Jeon JG
Probiotics reduced organoleptic and volatile sulphur compound scores versus placebo.
Efficacy of probiotics in multiple sclerosis: a systematic review of preclinical trials and meta-analysis of randomized controlled trials
Jiang J, et al
Meta-analysis of RCTs enrolling 173 patients with MS receiving probiotics revealed significant beneficial effects of probiotic supplementation on mental health, with very low certainty of evidence.
Probiotics in the treatment of diverticular disease. A systematic review
Lahner E, Bellisario C, Hassan C
Available studies of probiotics in diverticular disease were small and heterogeneous, precluding firm conclusions on efficacy.
Treating asthma patients with probiotics: a systematic review and meta-analysis
Probiotic supplementation produced small, heterogeneous improvements in asthma symptom measures.
Probiotics for the Prevention of Antibiotic-Associated Diarrhea in Adults
Goldenberg JZ, Yap C, Lytvyn L +4 more
Probiotics are effective for preventing antibiotic-associated diarrhoea.
Probiotics as adjunctive treatment for chronic rhinosinusitis: a randomized controlled trial
Mukerji SS, Pynnonen MA, Kim HM +2 more
Oral use of the probiotic strain Lactobacillus rhamnosus R0011 was not more effective than placebo.
Effect of Probiotics on Incident Ventilator-Associated Pneumonia in Critically Ill Patients: A Randomized Clinical Trial
Johnstone J, et al.
Among critically ill patients requiring mechanical ventilation, administration of the probiotic L rhamnosus GG compared with placebo, resulted in no significant difference in the development of ventilator-associated pneumonia. These findings do not support the use of L rhamnosus GG in critically ill patients.
The effect of Saccharomyces boulardii supplementation on Helicobacter pylori eradication in children: a systematic review and meta-analysis of randomized controlled trials.
Liu LH, Han B, Tao J +1 more
S. boulardii in combination with STT was more effective than STT alone (intention-to-treat analysis: 87.7% vs. 75.9%, RR = 1.14, 95% CI: 1.10-1.19, P < 0.00001).
Saccharomyces boulardii as a Probiotic Supplement in Helicobacter pylori Eradication Therapy: A Meta-analysis
Westphal JR, Koch N, Vilchez-Vargas R +1 more
The supplementation of S. boulardii to H. pylori therapy caused a significant increase in overall eradication rates and a significant decrease in overall diarrhea, nausea, and epigastric pain rates.
Probiotics for the treatment and prevention of small intestinal bacterial overgrowth: a systematic review and meta-analysis
Zhong C, Qu C, Wang B +2 more
Probiotics achieved a pooled SIBO decontamination rate of 62.8% and reduced abdominal pain, but did not prevent SIBO onset
Bifidobacterium animalis subsp. lactis Bi-07 supports lactose digestion in vitro and in randomized, placebo- and lactase-controlled clinical trials
Rasinkangas P, et al
Bi-07 has high lactase activity, and in 2 clinical trials, it supported lactose digestion in individuals with lactose intolerance.
Probiotic Supplementation Improves Cognitive Function and Mood with Changes in Gut Microbiota in Community-Dwelling Older Adults
Probiotic supplementation improves cognitive function and mood with changes in gut microbiota in community-dwelling older adults.
Dose-response effect of Bifidobacterium lactis HN019 on whole gut transit time and functional gastrointestinal symptoms in adults
Waller PA, Gopal PK
Bifidobacterium lactis HN019 shortened whole gut transit time in a dose-related manner
Probiotics for adults with major depressive disorder compared with antidepressants: a systematic review and network meta-analysis
Zhao X, et al
Probiotics, compared with antidepressants and placebo, may be efficacious as an adjunct or standalone therapy for treating MDD.
Effect of probiotics and prebiotics on natural killer cell activity: a systematic review of human trials
Gill HS, Rutherfurd KJ, Cross ML
Probiotic supplementation significantly increased natural killer cell tumoricidal activity in elderly participants
The probiotic Bacillus subtilis BS50 decreases gastrointestinal symptoms in healthy adults: a randomized, double-blind, placebo-controlled trial
Garvey SM, Mah E, Blonquist TM +2 more
BS50 increased the proportion of participants showing improvement from baseline to week 6 in the composite score for bloating, burping, and flatulence (47.4% vs. 22.2%)
Oral Probiotics to Prevent Recurrent Vulvovaginal Infections During Pregnancy: Multicenter Double-Blind, Randomized, Placebo-Controlled Trial
Oral probiotics were effective in secondary prevention of vulvovaginal infections including candidiasis during pregnancy.
Comparative efficacy of diverse therapeutic regimens for small intestinal bacterial overgrowth: a systematic network meta-analysis
Zhang Q, Li H, Chen C +1 more
The management of small intestinal bacterial overgrowth (SIBO) involves a range of therapeutic options such as antibiotics, probiotics, and prokinetic agents, yet their comparative clinical efficacy remains poorly characterized.
The Efficacy and Safety of Probiotics for Allergic Rhinitis: A Systematic Review and Meta-Analysis
Luo C, Peng S, et al
Probiotic supplement seems to be effective in ameliorating allergic rhinitis symptoms and improving the quality of life, but there is high heterogeneity in some results after subgroup analysis.
Effect of probiotics on oral candidiasis: a systematic review and meta-analysis
Mundula T, Ricci F, Barbetta B
Probiotics reduced oral Candida colonisation versus control.
Saccharomyces cerevisiae CNCM I-3856 in irritable bowel syndrome: An individual subject meta-analysis
Cayzeele-Decherf A, Pelerin F, Leuillet S +6 more
An individual patient data meta-analysis was performed on two randomized clinical trials studying the effect of S. cerevisiae CNCM I-3856 supplementation on gastrointestinal (GI) symptoms in IBS subjects.
A double-blind randomized placebo-controlled trial of probiotics in systemic sclerosis associated gastrointestinal disease
Low AHL, Teng GG, Pettersson S
Whilst there was no clear improvement in overall GI symptoms after 60 days, we observed significantly improved GI reflux after 120 days of probiotics. The trial confirmed safety of multi-strain probiotics in SSc patients.
Probiotics for preventing acute upper respiratory tract infections
Probiotics may modestly reduce upper respiratory infection episodes, but certainty of evidence is low.
A randomized, controlled trial of lactic acid bacteria for idiopathic hyperoxaluria
Goldfarb DS, Modersitzki F, Asplin JR
In this randomized, placebo-controlled trial, Oxadrop did not reduce urinary oxalate excretion in participants with idiopathic hyperoxaluria.
Evaluation of an Immunomodulatory Probiotic Intervention for Veterans With Co-occurring Mild Traumatic Brain Injury and Posttraumatic Stress Disorder: A Pilot Study
Brenner LA
No between-group differences were found on a subjective measure of stress responsivity; CRP decreased relative to placebo, approaching significance.
Probiotics as a prophylaxis to prevent oral candidiasis in patients with Sjogren's syndrome: a double-blinded, placebo-controlled, randomized trial
Kamal Y
The tested probiotic product may represent an unconventional method to reduce candidal colonization, to prevent oral candidosis in patients with Sjogren's syndrome.
Probiotic, prebiotic, synbiotic and fermented food supplementation in psychiatric disorders: A systematic review of clinical trials
Probiotic, prebiotic and fermented food interventions were evaluated across psychiatric disorders, with only one Tourette syndrome trial identified.
A Randomized Clinical Trial to Evaluate the Efficacy of an Oral Probiotic in Acne Vulgaris
An oral probiotic reduced inflammatory acne lesion counts compared with placebo.
Probiotics for treatment of chronic constipation in children
Wallace C, Sinopoulou V, Gordon M +1 more
The available evidence does not support probiotics as an effective treatment for functional constipation in children.
Systematic review with meta-analysis: the efficacy of prebiotics, probiotics, synbiotics and antibiotics in irritable bowel syndrome
Ford AC, Harris LA, Lacy BE +2 more
Probiotics appear to be an effective treatment for IBS, although which individual species and strains are the most beneficial remains unclear.
A randomized controlled trial of a probiotic combination VSL#3 and placebo in irritable bowel syndrome with bloating
Kim HJ, Vazquez Roque MI, Camilleri M +3 more
Treatment with VSL# 3 was associated with reduced flatulence over the entire treatment period (placebo 39.5 +/- 2.6 vs VSL# 3 29.7 +/- 2.6, P = 0.011)
Probiotics for celiac disease: a systematic review and meta-analysis of randomized controlled trials
Seiler CL, Kiflen M, Stefanolo JP
Probiotics did not significantly improve celiac symptoms or histology despite microbiota changes.
Efficacy of oral probiotics in patients with acne: a systematic review and meta-analysis of randomized trials
Lin HW, Tam KW, Huang YC
After the 12-week intervention, probiotics significantly alleviated disease severity grading.
Treatment for recurrent vulvovaginal candidiasis (thrush)
Cooke G, et al
Evidence for complementary and alternative treatments of recurrent vulvovaginal candidiasis is of low certainty.
Probiotic as an adjuvant therapy in chronic urticaria: a blinded randomized controlled clinical trial
Atefi N, Fallahpour M, Sharifi S +3 more
Combination of probiotic and antihistamines had no statistically significant different efficacy than the antihistamine alone, based on UAS7 score.
Probiotics in infants for prevention of allergic disease
Probiotic supplementation in infancy did not clearly prevent allergic disease.
The effect of yogurt fortified with Lactobacillus acidophilus and Bifidobacterium sp. probiotic in patients with lactose intolerance
Masoumi SJ, et al
Probiotic yogurt fortified with L. acidophilus and Bifidobacterium sp. could safely and effectively decrease lactose intolerance symptoms and HBT.
Probiotics as a complementary treatment in systemic lupus erythematosus: A systematic review
Mirfeizi Z, et al
Probiotics may be used in conjunction with other treatments to manage SLE. Nonetheless, current data is limited.
Efficacy and safety of gut microbiota-based therapies in autoimmune and rheumatic diseases: a systematic review and meta-analysis of 80 randomized controlled trials
Gut microbiota-based therapies showed limited and heterogeneous benefit across autoimmune and rheumatic diseases.
Lactobacillus rhamnosus GG versus Placebo for Acute Gastroenteritis in Children
Schnadower D, Tarr PI, Casper TC +3 more
Among preschool children with acute gastroenteritis, those who received a 5-day course of L. rhamnosus GG did not have better outcomes than those who received placebo.
Therapeutic Evaluation of Bifidobacterium animalis subsp. lactis MH-02 as an Adjunctive Treatment in Patients with Reflux Esophagitis: A Randomized, Double-Blind, Placebo-Controlled Trial
Gan L, Wang Y, Huang S +1 more
Bifidobacterium animalis subsp. lactis MH-02 as an adjunctive treatment improved clinical symptoms in patients with reflux esophagitis.
Effects of oral supplementation of probiotics on body weight and visceral fat in obese patients: a meta-analysis and systematic review
Probiotic supplementation produced small reductions in body weight and visceral fat in obese patients.
Systematic review and meta-analysis: Efficacy of patented probiotic, VSL#3, in irritable bowel syndrome
Connell M, Shin A, James-Stevenson T +3 more
No significant differences were observed for abdominal pain (SMD = -0.03; 95% CI -0.29 to 0.22), bloating (SMD = -0.15; 95% CI -0.40 to 0.11)
Efficacy of a multi-strain probiotic on digestive symptoms and enzyme-related maldigestion: a randomized controlled trial
Ojetti V, Ianiro G, Tortora A +3 more
Probiotic supplementation reduced bloating and flatulence scores significantly versus placebo
Probiotics on chronic urticaria: A randomized clinical trial study
Dabaghzadeh A, Ghaffari J, Moradi S +1 more
Probiotic consumption along with antihistamines significantly improved the activity of urticaria but not the quality of life of patients.
Efficacy of Probiotic Supplements on Brain-Derived Neurotrophic Factor, Inflammatory Biomarkers, Oxidative Stress and Cognitive Function
Probiotic supplementation modestly increased BDNF and reduced inflammatory markers.
Use of a Novel Probiotic Formulation to Alleviate Lactose Intolerance Symptoms - a Pilot Study
Gingold-Belfer R, et al
Normalization of LHBT was obtained in only two patients (25%).
Multicenter Trial of a Combination Probiotic for Children with Gastroenteritis
Freedman SB, Williamson-Urquhart S, Farion KJ +3 more
In children with acute gastroenteritis, the probiotic did not prevent the development of moderate-to-severe gastroenteritis within 14 days after enrollment.
Probiotics for preventing acute upper respiratory tract infections
Hao Q, Dong BR, Wu T
Probiotics reduced the number of participants experiencing acute upper respiratory infections
The Role of Probiotics in the Treatment of Vulvovaginal Candidiasis: A Systematic Review and Meta-Analysis
et al
Probiotics added to antifungal therapy improved short-term clinical and mycological cure rates in vulvovaginal candidiasis.
Comparative efficacy of probiotic, prebiotic, and synbiotic interventions in children with functional abdominal pain disorders: a systematic review and network meta-analysis
Yang Y, Li Y, Yan X +1 more
Given their biological plausibility, probiotics have emerged as a promising therapy, yet evidence remains inconsistent due to strain-specific effects and heterogeneous study designs.
Association of prebiotic/probiotic intake with MASLD: evidence from NHANES and randomized controlled trials
Wang S, Zhang R, Guo P +1 more
The analysis included randomized controlled trials of liver function in patients with MASLD or nonalcoholic steatohepatitis treated with probiotics, prebiotics, or yogurt for a minimum of 6 months.
Probiotics as a therapeutic strategy in obesity and overweight: a systematic review
Probiotic effects on body weight in overweight and obese adults were inconsistent and strain-specific.
The efficacy of probiotics, prebiotics or synbiotics in scleroderma: A systematic review
Wach AA, Storman D, Więckowski K +1 more
The use of probiotic formulas brings benefit in treatment of various autoimmune diseases, but the evidence for scleroderma is still not exhaustive.
Probiotics for preventing acute upper respiratory tract infections
Hao Q, Dong BR, Wu T
Probiotics were better than placebo in reducing the number of participants experiencing episodes of acute upper respiratory tract infection.
Effects of probiotics, prebiotics, and synbiotics on polycystic ovary syndrome: a systematic review and meta-analysis
Li Y, et al.
Overall, the meta-analysis demonstrates that probiotic, prebiotic, or synbiotic administration is an effective and safe intervention for modifying IR and lipid profiles.
Comparing the Effect of Probiotic and Fluconazole on Treatment and Recurrence of Vulvovaginal Candidiasis: a Triple-Blinded Randomized Clinical Trial
et al
Probiotic treatment achieved cure rates comparable to fluconazole with lower recurrence at follow-up.
The effect of probiotics on functional constipation in adults: a systematic review and meta-analysis of randomized controlled trials
Dimidi E, Christodoulides S, Fragkos KC +2 more
Probiotics reduced whole gut transit time, increased stool frequency, and improved stool consistency in adults with functional constipation.
Randomised clinical trial in women with recurrent vulvovaginal candidiasis: efficacy of probiotics and lactoferrin as maintenance treatment
Russo R, et al
Oral probiotics with lactoferrin as maintenance therapy reduced recurrence of vulvovaginal candidiasis versus control.
Prebiotics and probiotics for depression and anxiety: A systematic review and meta-analysis of controlled clinical trials
Liu RT, Walsh RFL, Sheehan AE
Probiotics produced a significant, albeit small, reduction in depression and anxiety symptoms relative to control conditions.
Probiotics for treating eczema
Makrgeorgou A, Leonardi-Bee J, Bath-Hextall FJ +4 more
Current evidence indicates that probiotics probably make little or no difference in improving patient-rated eczema symptoms.
Probiotics and Their Role in Gastrointestinal Disorders
Hungin AP, Mulligan C, Pot B +9 more
Probiotics modulate the gut microbiota and have a role in the management of several gastrointestinal disorders.
Efficacy of prebiotics, probiotics, and synbiotics in irritable bowel syndrome and chronic idiopathic constipation: systematic review and meta-analysis
Ford AC, Quigley EM, Lacy BE +6 more
Probiotics reduced global IBS symptoms and abdominal pain, with a relative risk of persistent symptoms of 0.79.
Probiotic therapy for the treatment of spondyloarthritis: a randomized controlled trial
Jenks K, Stebbings S, Burton J +3 more
Probiotic therapy produced no significant improvement in BASDAI, BASFI or quality of life in spondyloarthritis.
Safety Information
Potential Side Effects
Transient bloating, flatulence and mild abdominal discomfort in the first few days are common and usually settle within a week. Serious adverse events are rare in immunocompetent people. Case reports of bacteraemia and fungaemia exist almost exclusively in patients who are severely immunocompromised, critically ill or have central venous access. One trial in severe acute pancreatitis found increased mortality with a multi-strain probiotic, which is why probiotics are avoided in that setting.
Contraindications
Severe immunosuppression, neutropenia, central venous catheters, severe acute pancreatitis and critical illness. Use caution in premature infants outside of neonatal-unit protocols.
Drug Interactions
- Antibiotics (separate by 2+ hours)
Pregnancy & Breastfeeding
Pregnancy: likely_safe
Breastfeeding: likely_safe
Dosage Guidelines
Dosage Used in Studies
10-50 billion CFU
Best Time to Take
Morning on empty stomach or before bed
Best Form
Multi-strain capsules
Bioavailability
Survival through stomach acid varies by strain. Enteric-coated or refrigerated formulations may protect viability. Multi-strain often more effective.
Dosing by Goal
| Goal | Dose | Notes |
|---|---|---|
| Antibiotic-associated diarrhoea prevention | S. boulardii 500-1000 mg daily, or L. rhamnosus GG 10-20 billion CFU daily | Start within 48 hours of the first antibiotic dose — later starts lose most of the benefit. Continue for one to two weeks after the antibiotic course ends. Separate bacterial probiotics from the antibiotic by two hours; S. boulardii needs no separation. |
| Acute infectious diarrhoea in children | L. rhamnosus GG 10 billion CFU daily, or S. boulardii 250-750 mg daily | For 5-7 days. Shortens duration by roughly 24 hours. Oral rehydration remains the priority. |
| IBS | B. infantis 35624 at 1 billion CFU daily, or a multi-strain product as labelled | Give it four weeks. If there is no change by then, that product is not working — try a different strain rather than a higher dose. |
| Pouchitis maintenance | High-dose multi-strain, 450-900 billion CFU daily | Under gastroenterology supervision. |
Forms Compared
Saccharomyces boulardii CNCM I-745
Best for Antibiotic-associated diarrhoea, travellers diarrhoea
A yeast, so unaffected by concurrent antibiotics — can be taken at the same time. Avoid in central-line patients and severe immunocompromise due to rare fungaemia reports.
Lactobacillus rhamnosus GG (ATCC 53103)
Best for Paediatric acute gastroenteritis, antibiotic-associated diarrhoea
The single most studied probiotic strain. Shortens acute diarrhoea in children by roughly a day.
Bifidobacterium infantis 35624
Best for IBS
The strain behind the original Align trials; modest improvement in global IBS symptoms and bloating.
Multi-strain formulations (e.g. VSL#3-type high-dose blends)
Best for Pouchitis, ulcerative colitis maintenance
High colony counts in the hundreds of billions. Pouchitis is one of the strongest indications in the whole field.
Spore-forming Bacillus strains
Best for Shelf stability
Survive stomach acid and storage without refrigeration. Clinical evidence base is thinner than for the classic strains.
Fermented foods
Best for General microbial diversity
Yoghurt, kefir, kimchi and sauerkraut. Not standardised, but a randomised trial of high fermented-food intake showed increased microbiome diversity and reduced inflammatory markers.
Food & Timing
Most bacterial strains survive gastric transit better when taken with or just before a meal containing some fat; taking them on an empty stomach exposes them to the lowest gastric pH. Separate bacterial probiotics from antibiotic doses by at least two hours. Saccharomyces boulardii is a yeast and is unaffected by antibiotics, so timing is flexible.
Medical Disclaimer
The information provided on this website is for educational and informational purposes only and is not intended as a substitute for professional medical advice, diagnosis, or treatment. Always seek the advice of your physician or other qualified health provider with any questions you may have regarding a medical condition or before starting any supplement regimen.
Individual results may vary. The statements on this website have not been evaluated by the Food and Drug Administration. Products and information are not intended to diagnose, treat, cure, or prevent any disease.