Swansea University Lancet study questions probiotic use

Prescribing probiotics for elderly patients at risk of diarrhoea from antibiotic use has become routine practice in some institutions. This Swansea University study, the largest of its kind ever undertaken and published on the Lancet’s website, questions their efficacy.

Nearly 3,000 patients participated in this multi-centre, double-blind, randomised trial. A microbial preparation (the ‘probiotic’) and a placebo were randomly allocated in identical capsules to older patients from different wards in five separate NHS hospitals. As a ‘double-blind’ trial, neither the patients nor the researchers knew who was receiving which preparation until the end of the trial when all data had been collected.

The patients were given a 21-day course of the capsules and were followed up for 8-12 weeks.  Compliance was good, with three-quarters of the patients taking the capsules for 14 or more days and over half completing the full 21 day course.

Diarrhoea occurred in just over 10% of the patients overall. However, it was equally common in patients taking the microbial preparation and those taking the placebo. Diarrhoea caused by Clostridium difficile (or “C. diff”) was uncommon – it occurred in about 1% of the patients. There was a slight reduction in C. diff diarrhoea occurrence in those taking the microbial preparation but the difference was very small – just 12 as opposed to 17 cases.

Stephen Allen is Professor of Paediatrics and International Health at Swansea University and is based at the medical college’s Institute of Life Science. He is the lead researcher on the study and explained the significance of its findings:

“Overall, we found no evidence that the bacterial preparation was a ‘probiotic’ in this group of patients. Also, several other health outcomes we recorded and quality of life were similar in patients taking the microbial preparation and those taking the placebo.

However, there is a large number of possible ‘probiotics’ that could be tested. What we need to do is go back to the lab to understand more about the underlying disease mechanisms that cause diarrhoea in people taking antibiotics and have evidence that a specific microbe has a good chance of working. Perhaps then we could mount another trial”.

Nick Daneman of the University of Toronto was invited by the Lancet to comment on the study’s findings. He found that: “‘Most prior probiotic research has involved small, single centre studies of variable quality. At the very least, the low absolute risk reductions in this study question the cost effectiveness of probiotics”.

He concludes: ‘The PLACIDE study is a large and rigorous negative study, and we must judge whether it can tip the balance of probiotic evidence’.

Commenting on the research, Professor Keith Lloyd, Dean and Head of the College of Medicine at Swansea University said: "Congratulations to Professor Allen and colleagues. This high quality study is typical of the excellent research being undertaken in Swansea University's College of Medicine - studies that make a real difference to human health and well-being."