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Vsl6.5
VSL#3 / Visbiome Research
Mostly mechanism / observational
24 peer-reviewed studies
What the evidence says
Mostly mechanism / observational
Most VSL#3 / Visbiome studies are mechanism or observational rather than RCTs that measure a clinical effect — keep findings provisional.
Most evidence is from high-quality meta-analyses and randomised trials published 2000–2026 with a typical study size of 50 participants.
Based on 24 studies · 6 meta-analyses · 10 RCTs · 1,705 total participants
Confidence
High confidence
By outcome
Ulcerative colitis
Mostly mechanism / observational13 studies
Pouchitis
Mostly mechanism / observational8 studies
Crohn's disease
Mostly mechanism / observational7 studies
IBS & general digestive symptomsStrong benefit specifically for pouchitis after ulcerative colitis surgery and modest benefit for active ulcerative colitis. No demonstrated benefit for IBS or general digestive comfort · 8-12 weeks
Mostly mechanism / observational7 studies
Safety profile
Mostly mechanism / observational6 studies
InflammationDirectly reduces mucosal inflammatory cytokines and helps induce remission in active ulcerative colitis as an add-on to standard therapy · 8-12 weeks
Too few graded studies2 studies
Liver disease & hepatic encephalopathy
Too few graded studies1 study
Therapeutic & clinical
Too few graded studies1 study
Active research area
8 studies in the last 5 years · Latest meta-analysis: 2023
200020132026
1Meta-Analysis2019
In plain English: Cochrane found 85% of participants maintained pouchitis remission versus 3% on placebo, while grading the evidence low certainty and reporting results under the name De Simone Formulation rather than a brand.
Nguyen N et al. · Cochrane Database Syst Rev (2019)
Chronic pouchitis maintenance: 85% (34/40) maintained remission at 9-12 months vs 3% (1/36) placebo — RR 20.24 (95% CI 4.28-95.81), low certainty
Prevention: 90% (18/20) had no acute pouchitis at 12 months vs 60% (12/20) placebo — RR 1.50 (1.02-2.21), low certainty
In plain English: Probiotics as a class showed no benefit for active ulcerative colitis, but restricting the analysis to this blend produced a significant effect — and nothing worked in Crohn's disease.
Derwa Y et al. · Aliment Pharmacol Ther (2017)
Probiotics as a class: no benefit for inducing remission in active UC, RR of failure 0.86 (0.68-1.08)
Restricted to this blend: RR of failure 0.74 (0.63-0.87)
Probiotics roughly equivalent to 5-ASA for preventing UC relapse: RR 1.02 (0.85-1.23)
In plain English: More robust randomized clinical trials are required to validate the efficacy and safety of diverse probiotic strains in IBD.
Ma Y, Yang D, Huang J, Liu K, Liu H, Wu H, Bao C. · Open life sciences (2024)
Currently, there are no definitive conclusions regarding the effectiveness of probiotics in CD.
The mechanism of probiotic treatment for IBD may be related to reducing oxidative stress, repairing the intestinal barrier, regulating intestinal flora balance, and modulating intestinal immune response.
Differences in the benefits of probiotics between CD and UC may be attributable to the different lesion extent and immune-mediated pathophysiology.
Nair SS, Kutty Narayanan A, Nair K, Mallick S, Zackariah NM, Biswas L, Praseedom R, G Nair BK, Surendran S. · BMJ open (2025)
The first 50 patients in the study protocol will undergo gut microbiome analysis using 16s metagenomic and nanopore sequencing to analyse the microbial composition before starting synbiotics/placebo and at 6 weeks after LDLT.
The results of the trial will be disseminated by presentation at national/international conferences and publication in peer-reviewed journals.
In plain English: The post-operative Crohn's trial missed its primary endpoint at day 90, though mucosal inflammatory cytokines were reduced.
Fedorak RN et al. · Clin Gastroenterol Hepatol (2015)
PRIMARY ENDPOINT MISSED: severe endoscopic lesions at day 90 in 9.3% on the probiotic vs 15.7% placebo (P=.19)
Among patients with non-severe lesions at day 90, severe endoscopic recurrence at day 365 was 10.0% on early treatment vs 26.7% on late treatment (P=.09) — also not significant
Aggregate severe recurrence rates 20.5% (early) vs 42.1% (late) were not statistically different
In plain English: The dedicated IBS meta-analysis found no effect on pain, bloating, stool consistency or quality of life, with only a non-significant trend toward improved overall response.
Connell M et al. · Neurogastroenterol Motil (2018)
Abdominal pain SMD -0.03 (95% CI -0.29 to 0.22) — no effect
Bloating SMD -0.15 (-0.40 to 0.11); normal stool consistency MD 0 (-0.09 to 0.08)
In plain English: In this trial with no control group, a decrease in depressive symptoms in healthy older volunteers was observed after a 2-month healthy diet intervention, independently of inflammation but with possible limitations due to participation.
Bourdel-Marchasson I et al. · Nutrients (2020)
A decrease of CES-D score was seen in the four arms (A: -40.0%, p = 0.001; B: -32.5%, p = 0.023; C: -42.8%, p = 0.004; and D: -33.3%, p = 0.21).
Within the subgroups of subjects with medium/high inflammation a similar decrease in CES-D score occurred in all groups (A: -44.8%, p = 0.021; B, -46.7%, p = 0.024; C, -52.2%, p = 0.039; D, -43.8%, p = 0.037).
The effect of interventions on CES-D was not related to baseline inflammation.
In plain English: Added to standard therapy it reduced disease activity scores, but the authors' own conclusion states that the rectal bleeding and remission findings do not reach statistical significance.
Tursi A et al. · Am J Gastroenterol (2010)
At least 50% disease activity decrease: 63.1% vs 40.8% (per protocol P=0.010; intention to treat P=0.031)
Improvement of 3 or more points in the UCDAI score: 60.5% vs 41.4% (per protocol P=0.017; intention to treat P=0.046)
Rectal bleeding: per protocol P=0.014 and intention to treat P=0.036 in the results table — BUT the authors' stated conclusion is that VSL#3 'improves rectal bleeding and seems to reinduce remission ... although these parameters do not reach statistical significance'
In plain English: The primary endpoint of preventing breakthrough hepatic encephalopathy was missed, though hospitalisations and liver scores improved.
In plain English: This blend beat placebo for both clinical remission and clinical response in active ulcerative colitis, and was statistically indistinguishable from faecal microbiota transplantation.
Dang X et al. · PLoS One (2020)
VSL#3 vs placebo for clinical remission: OR 2.40 (95% CI 1.49-3.88); clinical response OR 3.09 (95% CI 1.53-6.25)
Faecal microbiota transplantation vs placebo: remission OR 3.47 (1.93-6.25); response OR 2.48 (1.18-5.21)
Indirect comparison between FMT and VSL#3 was not significant for remission (RR 1.20, 0.70-2.06) or response (RR 0.95, 0.62-1.45)
In plain English: Blood immune activation markers in immunologic nonresponder individuals on effective antiretroviral treatment were not reduced by supplementation with DSFP; CD4+ T-cell activation may have been increased.
Rousseau RK et al. · Journal of acquired immune deficiency syndromes (1999) (2022)
Blood CD8 activation increased 0.82 percentage points (pp) in the probiotic arm (95% confidence interval: -1.23 to 2.87;) and decreased by 2.06 pp in the placebo arm (-4.81 to 0.70; between arms P = 0.097).
CD4+ T-cell activation (%HLA-DR+) decreased in the placebo arm [-3.79 pp (-7.32 to -0.26)] but increased in the probiotic arm [1.64 (-0.98 to 4.26); between arms P = 0.018].
Blood immune activation markers in immunologic nonresponder individuals on effective antiretroviral treatment were not reduced by supplementation with DSFP; CD4+ T-cell activation may have been increased.
Naseer M et al. · Current clinical pharmacology (2020)
The efficacy of prebiotics such as fructooligosaccharides and Plantago ovata seeds in ulcerative colitis are inconclusive and the data regarding the utility of prebiotics in pouchitis is limited.
The results of the clinical trials for remission induction and maintenance in active Crohn's disease or post-operative relapse with probiotics and prebiotics are inadequate and not very convincing.
Prebiotics and probiotics are safe, effective and have great therapeutic potential.
In plain English: Moreover, we suggest the need to search for more therapeutic possibilities, especially via the research and application of synbiotics and postbiotics.
Wei L et al. · European journal of pharmacology (2022)
The anti-cancer effect of individual probiotics has been extensively studied, and the exact curative effect of various probiotics has been found, but the anti-cancer effect of mixed probiotics is still not well summarized.
In this review, we discuss the positive effects of mixed probiotics on CRC and the related mechanisms of action, especially VSL#3 (VSL Pharmaceuticals, Inc., Gaithersburg, MD, USA), thus providing new ideas for the treatment of CRC.
Moreover, we suggest the need to search for more therapeutic possibilities, especially via the research and application of synbiotics and postbiotics.
In plain English: The aim of this review is to compare the gut-microbiota-related pathophysiological pathways and biomarkers between IBS and IBD, to summarize the microbiome-related medications that have already been studied in both diseases, and to suggest new potential therapeutic options based on the gut microbiota.
Pastras P, Aggeletopoulou I, Psalti V, Triantos C. · Pharmaceuticals (Basel, Switzerland) (2026)
Although the microbiota plays a key role in IBS and IBD pathophysiology, microbiome-based treatments remain limited, especially in IBD.
There are clinically available treatments in IBS (e.g., rifaximin, low-FODMAP diet), but in IBD, only the probiotic VSL#3 is guideline-approved in ulcerative colitis pouchitis prophylaxis.
Nevertheless, the dynamic nature of the microbiota continues to support the investigation of already studied (e.g., probiotics, fecal microbiota transplantation) and potential novel therapeutic approaches at the research level.