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Pro9.0
Probiotics Research
Likely helps
1,030 peer-reviewed studies
What the evidence says
Probably helps
Probiotics helped in about half (17/25) 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 258 participants.
Based on 1,030 studies · 282 meta-analyses · 591 RCTs · 42,766 total participants
Confidence
High confidence
What the studies found
17helped3unclear5didn't help· 1005 more without graded effect data
By outcome
Digestive healthImproved gut microbiome balance and digestive regularity within 2-4 weeks · 2-4 weeks
Probably helps854 studies
Therapeutic & clinical
Likely helps173 studies
Women's healthProvides essential nutrients for healthy pregnancy · Ongoing
Mostly mechanism / observational90 studies
Depression & moodReductions in depression symptoms in clinical samples; anxiety benefit is inconsistent and strain-/population-dependent · 4-8 weeks
Likely helps53 studies
Glucose & metabolic
Likely helps49 studies
Weight management
Mostly mechanism / observational44 studies
Cognitive function
Likely helps40 studies
Anxiety & stressAnxiety evidence is mixed — meta-analyses are null in general populations, with benefit mainly in clinically diagnosed samples · 4-8 weeks
Mostly mechanism / observational26 studies
Skin health
Mostly mechanism / observational20 studies
InflammationImproved digestion and regularity · 2-4 weeks
Probably helps19 studies
Immune supportMay reduce frequency and duration of respiratory infections · 4-8 weeks
Mostly mechanism / observational18 studies
Liver health
Mostly mechanism / observational16 studies
Heart & blood pressure
Mostly mechanism / observational15 studies
Joint pain & arthritis
Mostly mechanism / observational10 studies
Safety profile
Mostly mechanism / observational9 studies
Bone health
Mostly mechanism / observational8 studies
Cholesterol & lipids
Mostly mechanism / observational7 studies
Energy & fatigue
Mostly mechanism / observational6 studies
Fertility & reproductive
Mostly mechanism / observational6 studies
Sleep & insomnia
Mostly mechanism / observational5 studies
Vision & eye health
Too few graded studies2 studies
By the numbers
Pulled from 77 studies with measurable effects
Likely real effects
83%
across studies
People studied
43k
typical study: 258 people
Strongest designs
873
282 pooled, 591 randomised
Showed benefit
68%
17/25 studies
How long studies ran
1–3 months
4
3+ months
1
Populations Studied
General population6
Type 2 diabetes patients2
Cancer patients2
Adults2
Active research area
1,020 studies in the last 5 years · Latest meta-analysis: 2026
201220192026
1Meta-Analysisn=703 · large study2026
In plain English: Further studies with longer follow-up durations are needed to confirm these findings and explore the long-term benefits of probiotics in this population.
Chiou YY, Chiu TY, Chen MJ. · Nutrients (2026)
Background Autoimmune diseases affect 5-10% of the global population.
Subgroup analysis revealed that in rheumatoid arthritis (RA) patients, the probiotics group showed greater improvements in IL-6, IL-1β, and TNFα compared to the controls.
In multiple sclerosis (MS) patients, the probiotics group demonstrated greater improvements in hs-CRP.
2Intestinal barrier function improvementMeta-AnalysisCited 115×n=1,891 · large study2023
In plain English: Meta-analysis of data from a total of 26 RCTs (n = 1891) indicated that probiotics significantly improved gut barrier function measured by levels of TER (MD, 5.27, 95% CI, 3.82 to 6.72, P < 0.00001), serum zonulin (SMD, -1.58, 95% CI, -2.49 to -0.66, P = 0.0007), endotoxin (SMD, -3.20, 95% CI, -5.41 to -0.98, P = 0.005), and LPS (SMD, -0.47, 95% CI, -0.85 to -0.09, P = 0.02).
Zheng Y et al. · Frontiers in Immunology (2023)
Significant improvement in intestinal barrier markers
Reduced zonulin and endotoxin levels
Enhanced gut barrier integrity across multiple trials
3FEV1 in asthma patientsMeta-AnalysisCited 10×n=1,101 · large study2023
In plain English: 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.
4Periodontal pocket depth reductionMeta-AnalysisCited 16×n=1,290 · large study2024
In plain English: Combining PMPR with probiotics as adjuvants to subgingival instrumentation may be more effective in improving PPD and CAL.
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.
6Prevention of antibiotic-associated diarrheaMeta-AnalysisCited 25×n=4,691 · very large study2022
In plain English: We recommend that elderly individuals could be routinely distributed probiotics to prevent AAD development when receiving antibiotic treatment.
Zhang L et al. · BMC geriatrics (2022)
We recommend that elderly individuals could be routinely distributed probiotics to prevent AAD development when receiving antibiotic treatment.
7ASD behavioral symptoms improvementMeta-AnalysisCited 23×n=318 · medium study2024
In plain English: 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.
9Oral mucositis incidenceMeta-AnalysisCited 41×n=708 · large study2022
In plain English: 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).
11Anxiety symptomsMeta-Analysisn=1,527 · large study2018
In plain English: Probiotics did not significantly reduce symptoms of anxiety in humans (Hedges' g = -0.12, 95% CI -0.29-0.05, p = 0.151), and did not differentially affect clinical and healthy human samples.
Reis DJ et al. · PLoS One (2018)
Probiotics reduced anxiety-like behavior in animal models, mainly in diseased animals
No significant reduction in anxiety symptoms in human clinical trials
Only L. rhamnosus showed anxiolytic effects preclinically, in under-powered analyses