Probiotics Don’t Alleviate Diarrhea in Big Trial

UK researchers in charge of a large-scale trial on probiotics and antibiotic-related diarrhea have published a not-so-positive outcome. In 2941 adults aged 65 and older, probiotic supplements were no more effective than placebo in improving health conditions.

The multicenter PLACIDE Trial, now published in The Lancet, focused on adults who were on daily antibiotics, which are often associated with symptoms of diarrhea. Each participant was instructed to consume a daily probiotic capsule or identical placebo for three weeks. The probiotic capsule contained three bacterial strains that are frequently used in antibiotic-related diarrhea research: Lactobacillus acidophilus, Bifidobacterium bifidum, and Bifidobacterium lactis. It is speculated that probiotics are capable of restoring the balance of got flora that is compromised by frequent antiobiotic use.

Self-reporting revealed that, whether subjects were on probiotics or placebo, diarrhea rates were about the same (159 probiotic users and 153 placebo users). Frequency of serious adverse events in each group was also similar.

Stephen Allen, MD, lead author of the study and professor at Swansea University’s College of Medicine, said that while his results provide a well-powered and negative outcome for probiotics, this kind of probiotic research is still “hampered by a poor understanding of the pathophysiology of antibiotic-associated diarrhea.” The case does not look good for the three strains used in this study, but other specific strains of friendly bacteria may still carry anti-diarrheal mechanisms. Human factors such as age and diet may also modulate any effects that probiotic supplementation.

The PLACIDE Trial was funded in part by the United Kingdom’s National Institute for Health Research.