The Science Behind CDS22: What Decades of Clinical Research Actually Show

A closer look at the De Simone Formulation — one of the most studied multi-strain probiotics in gastroenterology — and what the evidence really supports.

Most probiotic marketing leans on vague claims: "supports gut health," "millions of live cultures," "clinically proven." CDS22 is different in one specific, checkable way — it contains the De Simone Formulation, an eight-strain probiotic blend that has been the subject of more published clinical research than almost any other probiotic on the market, including trials referenced directly in gastroenterology society guidelines.

We think it's worth explaining what that research actually says — including where the evidence is strong, and where it's still early — rather than just asserting benefits.

What is the De Simone Formulation?

Developed by Professor Claudio De Simone, this is a precise blend of eight bacterial strains from the Lactobacillus, Bifidobacterium, and Streptococcus families, manufactured to a fixed ratio and high potency per dose. It was sold under the VSL#3 name until 2016, and is now supplied as CDS22 in the UK, Vivomixx in parts of Europe, and Visbiome in the US — following a split between the formula's original inventor and the VSL#3 brand's later manufacturer. It's important to know that CDS22 follows the original De Simone Formulation; not every product still using the "VSL#3" name today uses the same manufacturing process.

What the clinical research shows

Ulcerative colitis — as an adjunct, alongside standard treatment

Several small-to-moderate randomized trials have looked at this formulation as an add-on to standard therapy in mild-to-moderate ulcerative colitis. In one placebo-controlled trial, adding the probiotic to balsalazide improved remission rates compared with balsalazide or mesalazine alone. In another, adding it to standard treatment during a relapse improved response rates over an eight-week period. A pediatric trial found it helped both induce and maintain remission in children with active disease.

Important context: this is evidence for use alongside prescribed treatment, not instead of it, and the American Gastroenterological Association's broader 2020 guideline on probiotics in GI disease still recommends probiotics for ulcerative colitis only in the context of a clinical trial, citing a need for larger, higher-quality studies. The formulation's own trial results are promising but shouldn't be read as a green light to self-treat.

Pouchitis — the one condition where it's specifically named in guidelines

This is the strongest and most specific evidence base. Multiple placebo-controlled trials — going back over 20 years — have tested this exact formulation for preventing and maintaining remission from pouchitis, a common complication after ileal pouch surgery for ulcerative colitis. The results were consistent enough that the AGA's 2020 and 2024 guidelines both name this eight-strain combination specifically, recommending it over no probiotic or other probiotics for people managing recurrent pouchitis. The European Crohn's and Colitis Organisation references it in pouch-management guidance as well.

Even here, the recommendation is conditional and based on low-certainty evidence by the guideline panels' own grading — real, but not settled science. It's specifically for people already under a gastroenterologist's care.

IBS — symptom relief in several trials

A handful of randomized, placebo-controlled trials have tested this formulation in irritable bowel syndrome, including diarrhoea-predominant IBS and IBS with bloating, generally finding improvements in bloating and reduced gut transit time compared with placebo. A pediatric crossover trial found symptom improvement in children with IBS. Effect sizes vary study to study, and IBS research broadly is complicated by strong placebo responses, so this is best read as "promising, not definitive."

Preventing antibiotic-associated diarrhoea

One double-blind, placebo-controlled UK trial found this formulation reduced the incidence of antibiotic-associated diarrhoea in hospitalised patients — a common, disruptive side effect of antibiotic courses.

Why the formulation matters more than the strain count

Not all multi-strain probiotics behave the same way, even with similar strain lists — manufacturing process, exact ratios, and strain interactions all affect what actually survives and does something in the gut. Much of the research above is specific to this formulation's precise composition, which is part of why "high CFU count" alone isn't a reliable way to compare probiotics.

What CDS22 is — and isn't

CDS22 is a food supplement, not a registered medicine, and it isn't intended to diagnose, treat, cure, or prevent any disease. If you're managing a diagnosed digestive condition — including IBD, IBS, or pouchitis — this research is worth discussing with your doctor or gastroenterologist, but it doesn't replace their care or your prescribed treatment.

Selected clinical references

• Bibiloni R, et al. VSL#3 probiotic-mixture induces remission in patients with active ulcerative colitis. Am J Gastroenterol. 2005;100(7):1539-46.
• Sood A, et al. The probiotic preparation, VSL#3 induces remission in patients with mild-to-moderately active ulcerative colitis. Clin Gastroenterol Hepatol. 2009;7(11):1202-9.
• Tursi A, et al. Treatment of relapsing mild-to-moderate ulcerative colitis with the probiotic VSL#3 as adjunctive to a standard pharmaceutical treatment. Am J Gastroenterol. 2010;105(10):2218-27.
• Miele E, et al. Effect of a probiotic preparation (VSL#3) on induction and maintenance of remission in children with ulcerative colitis. Am J Gastroenterol. 2009;104(2):437-43.
• Gionchetti P, et al. Oral bacteriotherapy as maintenance treatment in patients with chronic pouchitis. Gastroenterology. 2000;119(2):305-9.
• Gionchetti P, et al. Prophylaxis of pouchitis onset with probiotic therapy. Gastroenterology. 2003;124(5):1202-9.
• Mimura T, et al. Randomized clinical trial of probiotic therapy for maintenance of remission in chronic pouchitis. Gut. 2004.
• Kim HJ, et al. A randomized controlled trial of a probiotic combination VSL#3 and placebo in IBS with bloating. Neurogastroenterol Motil. 2005;17(5):687-96.
• Guandalini S, et al. VSL#3 improves symptoms in children with irritable bowel syndrome. J Pediatr Gastroenterol Nutr. 2010;51(1):24-30.
• Selinger CP, et al. Probiotic VSL#3 prevents antibiotic-associated diarrhoea in a double-blind, randomized, placebo-controlled clinical trial. J Hosp Infect. 2013;84(2):159-65.
• Barnes EL, et al. AGA Clinical Practice Guideline on the Management of Pouchitis and Inflammatory Pouch Disorders. Gastroenterology. 2024;166(1):59-85.
• Su GL, et al. AGA Clinical Practice Guidelines on the Role of Probiotics in the Management of Gastrointestinal Disorders. Gastroenterology. 2020;159(2):697-705.