The Clinical Standard in Probiotic Medical Foods
VSL#3® delivers one of the most concentrated and diverse probiotic formulations available, combining 8 complementary strains from 3 genera. Formulated as a medical food, it is intended for the dietary management of IBS, ulcerative colitis, and pouchitis—conditions where modulation of the gut microbiota plays a key role in patient outcomes.
Supported by clinical use and published research, VSL#3® is the #1 gastroenterologist-recommended multi-strain probiotic brand.† It’s a trusted choice for specialists seeking consistency, potency, and formulation integrity.
Backed by Clinical Use and Research
VSL#3® has been extensively evaluated in clinical and mechanistic studies examining its role across gastrointestinal and microbiome-related conditions. Clinically used for the dietary management of IBS, ulcerative colitis, and pouchitis, additional studies have expanded understanding of how its multi-strain formulation supports gut barrier integrity, microbiota balance, and systemic inflammatory pathways.
This growing body of evidence continues to support VSL#3® as a well-characterized, high-potency medical food trusted by gastroenterologists for patients requiring targeted microbiome support.
Clinical Evidence Supporting VSL#3® in the Dietary Management of IBS
VSL#3® vs. the Low FODMAP Diet
In a randomized, web-based clinical study published in the Journal of Medical Internet Research (Ankersen et al., 2021), adults with irritable bowel syndrome (IBS) received either a four-week course of VSL#3® or followed a Low FODMAP diet. Both groups achieved clinically meaningful reductions in symptom severity scores, and outcomes with VSL#3® were comparable to the Low FODMAP diet.
Importantly, among patients who did not initially respond to the diet, the majority experienced improvement when switched to VSL#3®, indicating that its use may complement or substitute restrictive dietary interventions when those approaches are not feasible or effective.
These findings reinforce the role of VSL#3® as a practical and evidence-based option for the dietary management of IBS under medical supervision.
VSL#3® vs. Rifaximin in IBS-D
A separate open-label, randomized clinical study conducted in India (Goyal et al., 2021) compared VSL#3® (112.5 billion CFU twice daily) with rifaximin (550 mg twice daily) in adults meeting Rome IV criteria for diarrhea-predominant IBS (IBS-D). Over six weeks, both groups showed significant improvements in abdominal pain, stool frequency, and stool consistency.
VSL#3® demonstrated non-inferiority to rifaximin across key endpoints, with greater improvement in stool parameters at several time points. These results suggest that VSL#3® offers a well-tolerated, non-antibiotic alternative for the dietary management of IBS-D, aligning with its established role as a medical food formulated for use under physician supervision.
Summary
Across controlled dietary and pharmacologic comparisons, VSL#3® has consistently shown clinically meaningful outcomes in patients with IBS.
Together, these studies strengthen the evidence base for VSL#3® as a trusted medical food for the dietary management of IBS, particularly when dietary restriction or antibiotic therapy may not be suitable.
Confidence in Every Dose
VSL#3® provides healthcare professionals with a clinically directed, clearly labeled medical food that can be confidently recommended for patients managing IBS, ulcerative colitis, and pouchitis through diet.
Each formulation is standardized for potency, strain diversity, and stability—delivering 8 probiotic strains from 3 genera and maintaining CFU counts through the “best by” date when stored as directed.
VSL#3® is available through multiple professional and retail channels, including pharmacies, vsl3.com, Amazon, and Fullscript, ensuring consistent patient access and continuity of care.
Please confirm you are a Health Care Provider before entering this portion of the website.
References
Ankersen D et al. J Med Internet Res. 2021; 23(12): e26083.
Goyal S et al. World J Pharm Res. 2021; 10(3): 1516–1527.