Irritable bowel syndrome (IBS) and Symprove study overview

This independent study was carried out at King’s College London by Dr Guy Sisson and Professor Ingvar Bjarnason to establish the efficacy of Symprove in irritable bowel syndrome (IBS).

It was a randomised, double-blind, placebo-controlled study and was one of the first to address the efficacy of a probiotic using standards equivalent to a drug trial.

The study was carried out on 186 IBS sufferers, mostly with moderate to severe symptoms. They each receive either a daily dose of Symprove or an identical placebo liquid for three months.

The study looked at the effects of Symprove on:

  • Pain
  • Constipation
  • Diarrhoea

It concluded that significant improvement was seen in four weeks and continued through the full 12 weeks. 

A statistically significant improvement in overall symptom severity in patients with IBS was seen

The results of the study were published in the Alimentary Pharmacology & Therapeutics journal ( AP&T) in 2014.

Watch Dr Sisson talk about this study in the video below.

Study summary from AP&T

Name of study

Randomised clinical trial: a liquid multi-strain probiotic vs. placebo in the irritable bowel syndrome – a 12 week double-blind study


The importance of interactions between the host and gut microbiota in the pathogenesis of irritable bowel syndrome (IBS) is becoming increasingly apparent. Probiotics offer a potential new treatment for IBS, but current results are conflicting, largely as a result of poorly designed trials and nonstandardisation of outcome measures.


To assess the efficacy of a liquid, multi-strain probiotic (Symprove) in IBS.


A single-centre, randomised, double-blind, placebo-controlled trial of adult patients with symptomatic IBS. Patients received 12 weeks of treatment with the probiotic or placebo (1 mL/kg/day). The primary efficacy measure was the difference in change in the IBS symptom severity score (IBS-SSS) between probiotic vs. placebo at week 12. Secondary outcome measures included change in the IBS quality of life (IBS-QOL) score and change in the IBS-SSS symptom component scores.


A total of 186 patients were randomised and 152 patients completed the study. The mean change in IBS-SSS was −63.3 probiotic vs. −28.3 placebo. The mean difference in the IBS-SSS was statistically significant [−35.0 (95% CI; −62.03, −7.87); P = 0.01]. There was no significant improvement in the IBS-QOL. No serious adverse events were reported.


The multi-strain probiotic was associated with a statistically significant improvement in overall symptom severity in patients with IBS, and was well tolerated. These results suggest this probiotic confers benefit in IBS and deserves further investigation

Read the full study