We use essential cookies (authentication, your saved goals/stack) by default. With your permission we'll also enable privacy-respecting analytics (Vercel Web Analytics, anonymous load-time metrics) and error-replay diagnostics (Sentry — DOM snapshots only when an error fires) so we can fix bugs faster. Learn more
Pro9.0
Probiotics Research
Likely helpsHigh safety
134 peer-reviewed studies
What the evidence says
Probably helps
Probiotics helped in about half (18/26) of the studies that measured an effect — promising, but not unanimous.
Most evidence is from high-quality meta-analyses and randomised trials published 2012–2026 with a typical study size of 784 participants.
Based on 134 studies · 47 meta-analyses · 19 RCTs · 110,055 total participants
Confidence
High
What the studies found
18helped3unclear5didn't help· 108 more without graded effect data
By outcome
Digestive healthImproved gut microbiome balance and digestive regularity within 2-4 weeks · 2-4 weeks
Probably helps126 studies
Therapeutic & clinical
Likely helps33 studies
Depression & moodModest improvements in mood and anxiety (strain-dependent) · 4-8 weeks
Likely helps13 studies
Women's healthProvides essential nutrients for healthy pregnancy · Ongoing
Immune supportMay reduce frequency and duration of respiratory infections · 4-8 weeks
Probably helps6 studies
Cognitive function
Mostly mechanism / observational6 studies
InflammationImproved digestion and regularity · 2-4 weeks
Probably helps5 studies
Heart & blood pressure
Mostly mechanism / observational4 studies
Cholesterol & lipids
Mostly mechanism / observational3 studies
Weight management
Mostly mechanism / observational3 studies
Skin health
Mostly mechanism / observational3 studies
Liver health
Too few graded studies2 studies
Sleep & insomnia
Too few graded studies2 studies
Joint pain & arthritis
Too few graded studies2 studies
Fertility & reproductive
Too few graded studies2 studies
Bone health
Too few graded studies1 study
By the numbers
Pulled from 71 studies with measurable effects
Likely real effects
81%
across studies
People studied
110k
typical study: 784 people
Strongest designs
66
47 pooled, 19 randomised
Showed benefit
69%
18/26 studies
How long studies ran
1–3 months
2
3+ months
1
Populations Studied
General population4
IBS patients3
Adults3
Type 2 diabetes patients2
Active research area
121 studies in the last 5 years · Latest meta-analysis: 2026
201220192026
1Meta-Analysisn=2,841 · very large study2023
Future well-designed RCTs are needed to further confirm these findings.
Ye J et al. · Nutrients (2023)
Glutamine was superior in decreasing tumor necrosis factor-α (MD -25.2; 95% CrI [-32.62, -17.95]), whereas combined omega-3 and arginine supplementation was more effective in decreasing interleukin-6 (MD -61.41; 95% CrI [-97.85, -24.85]).
No nutritional supplements significantly maintained nutritional indicators in CRC patients.
Future well-designed RCTs are needed to further confirm these findings.
2Depression symptomsMeta-Analysisn=1,401 · large study2025
Probiotics showed substantial reductions in depression symptoms and moderate reductions in anxiety symptoms.
Asad A et al. · Nutrition reviews (2025)
Huge benefit
← WorseNo effectBetter →
Probiotics demonstrated a significant reduction in depression symptoms (SMD: -0.96; 95% CI: -1.31, -0.61) and a moderate reduction in anxiety symptoms (SMD: -0.59; 95% CI: -0.98, -0.19).
Prebiotics did not show a significant effect on depression (SMD: -0.28; 95% CI: -0.61, 0.04).
High heterogeneity was observed across studies, and subgroup analyses indicated that study duration and probiotic formulations contributed to the variation in effect sizes.
3Periodontal pocket depth reductionMeta-Analysisn=1,290 · large study2024
This meta-analysis examined the effects of Probiotics.
Mendonça CD et al. · BMC oral health (2024)
Network meta-analysis revealed significant mean differences in PPD for nine probiotic interventions, CAL for eighteen interventions, and BOP for eight interventions, with Lactobacillus demonstrating the most substantial effects.
Combining PMPR with probiotics as adjuvants to subgingival instrumentation may be more effective in improving PPD and CAL.
Lactobacillus emerged as the most comprehensive and effective among the studied probiotic.
4Pathogenic bacteria decolonizationMeta-Analysisn=2,871 · very large study2024
Protocol registration: PROSPERO (ID = CRD42021276045).
Rahman MN et al. · Gut microbes (2024)
Large benefit
← WorseNo effectBetter →
Likely real
This review aims to analyze available evidence from human-controlled trials to determine the effect size of probiotic interventions in decolonizing AMR pathogenic bacteria from the gut.
The persistence of pathogenic bacteria after treatment was 22%(probiotics) and 30.8%(placebo).
The pooled odds ratio was 0.59(95% CI:0.43-0.81), favoring probiotics with moderate certainty (p = 0.0001) and low heterogeneity (I2 = 49.2%, p = 0.0001).
7FEV1 in asthma patientsMeta-Analysisn=1,101 · large study2023
Conclusion: the use of probiotics in patients with asthma can improve lung inflammation and asthma symptoms, reduce the number of asthma attacks, and have no effect on lung function.
Xie Q et al. · Nutricion hospitalaria (2023)
No clear effect
← WorseNo effectBetter →
Meta-analysis was performed using Revman 5.4 software and the combined effect was evaluated by odds ratio (OR) or mean difference (MD) and 95 % confidence interval (CI).
There was no significant difference in forced expiratory volume in the first second (FEV1) (MD = 0.11, 95 % CI: -0.05, 0.26) and FEV1/FVC (%) (MD = 0.32, 95 % CI: -1.48, 2.12).
Results: a total of ten references were included, all of which were randomized controlled studies, and a total of 1,101 people were investigated.
11Oral mucositis incidenceMeta-Analysisn=708 · large study2022
We recommend the use of probiotics to prevent and treat oral mucositis during cancer therapy.
Liu YC et al. · International journal of molecular sciences (2022)
Noticeable benefit
← WorseNo effectBetter →
Likely real
Three trials using Lactobacilli-based probiotics reported that the incidence of oral mucositis in the probiotic group was significantly low (risk ratio [RR] = 0.84, 95% confidence interval [CI] = 0.77−0.93, p = 0.0004).
Seven trials reported a significantly low incidence of severe oral mucositis in the probiotic group (RR = 0.65, 95% CI = 0.53−0.81, p < 0.0001).
The requirement of enteral nutrition was significantly low in the probiotic group (odds ratio = 0.34, 95% CI: 0.13−0.92, p < 0.05).
12Acute infectious diarrhoea durationMeta-Analysisn=12,127 · very large study2020
Probiotics probably make little or no difference to the number of people who have diarrhoea lasting 48 hours or longer, and we are uncertain whether probiotics reduce the duration of diarrhoea.
Collinson S et al. · The Cochrane database of systematic reviews (2020)
Effect size was similar in the sensitivity analysis and marked heterogeneity persisted.
Effect size was similar and marked heterogeneity persisted in pre-specified subgroup analyses of the primary outcomes that included all studies.
In six trials (433 participants) of Lactobacillus reuteri, there was consistency amongst findings (I² = 0%), but risk of bias was present in all included studies.
13Clostridium difficile-associated diarrhea preventionMeta-Analysisn=9,955 · very large study2017
Based on this systematic review and meta-analysis of 31 randomized controlled trials including 8672 patients, moderate certainty evidence suggests that probiotics are effective for preventing CDAD (NNTB = 42 patients, 95% CI 32 to 58).
Goldenberg JZ et al. · The Cochrane database of systematic reviews (2017)
Huge benefit
← WorseNo effectBetter →
A complete case analysis (i.e. participants who completed the study) among trials investigating CDAD (31 trials, 8672 participants) suggests that probiotics reduce the risk of CDAD by 60%.
The incidence of CDAD was 1.5% (70/4525) in the probiotic group compared to 4.0% (164/4147) in the placebo or no treatment control group (RR 0.40, 95% CI 0.30 to 0.52; GRADE = moderate).
Twenty-two of 31 trials had missing CDAD data ranging from 2% to 45%.
15ASD behavioral symptoms improvementMeta-Analysisn=318 · medium study2024
Our study highlighted the significant improvement in ASD behavioral symptoms through probiotic supplementation.
Soleimanpour S et al. · Journal of psychiatric research (2024)
Noticeable benefit
← WorseNo effectBetter →
Likely real
This was shown by a pooled standardized mean difference (SMD) of -0.38 (95% CI: 0.58 to -0.18, p < 0.01).
Moreover, both multi-strain probiotics and single-strain interventions showed an overall significant improvement with a SMD of -0.53 (95%CI: 0.85 to -0.22) and -0.28 (95%CI: 0.54 to -0.02), respectively.
Our study highlighted the significant improvement in ASD behavioral symptoms through probiotic supplementation.
17Anxiety symptomsSystematic Reviewn=1,349 · large study2018
Probiotic supplementation showed a small but significant effect on anxiety symptoms.
Reis DJ et al. · Journal of Affective Disorders (2018)
Modest reductions in anxiety measures
Effects more pronounced in clinical populations
Strain-specific effects observed
18IBS symptom improvementMeta-Analysisn=54 · small study2024
However, the most effective probiotic combination or strain remains unclear, while prebiotics and synbiotics did not show significant improvement.
Wu Y et al. · Nutrients (2024)
Large benefit
← WorseNo effectBetter →
Prebiotics and synbiotics did not show significant improvement.
Network meta-analysis indicated the favorable effects of probiotics (OR = 0.53, 95% CI, 0.48 to 0.59) and FMT (OR = 0.46, 95% CI, 0.33 to 0.64) on IBS, with no serious adverse events reported.
However, the most effective probiotic combination or strain remains unclear, while prebiotics and synbiotics did not show significant improvement.
19Depressive symptomsMeta-Analysisn=844 · large study2020
Among the parameters determining the success of the given treatment, the most significant were probiotic composition (multi-strain formulation), the quantity of ingested psychobiotics and the duration of the study.
Zagórska A et al. · Beneficial microbes (2020)
Huge benefit
← WorseNo effectBetter →
Likely real
Probiotic administration reduced depressive symptoms among patients with depression in a statistically significant manner (standardised mean difference (SMD) = -0.87; 95% confidence interval (95% confidence interval): -1.66, -0.99; P=0.03).
Further evidence from larger and more rigorous studies with longer duration of probiotic administration, as well as well-defined populations, homogenous probiotic intervention and outcome measures, are needed to clarify the potential therapeutic effects of probiotics on psychiatric symptoms.
Based on the current literature, it seems that not all probiotic-/prebiotic-/dairy-rich diet-based treatments exhibited a psychobiotic effect on the CNS.