In Summary, for those who took the probiotics:

Benefits in NNT

  • Patients were helped by a 1-day decrease in the duration of their diarrhea

Harms in NNT

  • None were harmed

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Source: Allen SJ, Martinez EG, Gregorio GV, Dans LF. Probiotics for treating acute infectious diarrhoea. Cochrane Database Syst Rev. 2010 Nov 10;(11):CD003048. Review. PubMed PMID: 21069673.

Efficacy Endpoints: Duration of diarrhea, severity of diarrhea

Harm Endpoints: None reported

Narrative: Diarrhea is a major cause of mortality and morbidity worldwide, and treatment regimens often include a oral and/or intravenous rehydration, antibiotics, and anti-motility agents. The administration of probiotics have been proposed as an add-on intervention that may be able to decrease the duration and severity of diarrhea.

The Cochrane Review included 63 randomized controlled trials (56/63 in infants and children) of 8014 subjects with proven or presumed infectious diarrhea. Control groups were given no treatment or placebo. Administration of a probiotic agent decreased the mean duration of diarrhea by 24.76 hours (95% CI 15.9 – 33.6 hours) and stool frequency on day 2 by 0.8 stools (95% CI 0.45 – 1.14). No adverse effects were reported.

Caveats: While the aggregate study population was quite large most, of the studies were primarily involving children (6489 were infants and children under age 18). Additionally, included trials did not all use the WHO defined inclusion criteria, nor did they administer the same strain or dosage of probiotics. Further studies clearly need to be done to determine the most efficacious dose and probiotic strain (or combination of strains). Many studies were also in developing nations, making extrapolation to developed settings more difficult.

The considerable heterogeneity found in the studies deserves comment. Arguably it is inappropriate to pool the data from these studies, as the heterogeneous results are an indicator that the populations, settings, probiotic agents, and methods of these studies were all highly variable. Indeed they are likely too variable to be considered biologically similar, and therefore pooling these data may represent apples-to-oranges comparisons and combinations. We have chosen to report the pooled results, however, because in this case it seems that these results are a reasonable indicator of the likely impact of probiotics on diarrheal illness in almost all of the included settings and populations. In other words even if the review had been entirely narrative (i.e. did not include a meta-analysis of the studies but rather only provided a descriptive review) we believe that this result is a plausible and reasonable inference from the available data. Individual practitioners will, as always, have to use their judgment in the application of these data. In developing settings with dehydrated children these results are likely to be robust and relevant. In developed settings among adults probiotics may be considered more experimental.

Finally, while the studies did not address decreased long term morbidity or mortality with a probiotic agent, given the low cost of treatment and a significant decrease in a major patient oriented outcome we feel this is a meaningful effect.

Author: Viral Patel, MD

Published/Updated: September 28, 2011

  1. The Title Bar

    The title bar is color-coded with our overall recommendation.

    • Green: Benefits outweigh risks.
    • Yellow: Unclear risk/benefit profile.
    • Red: Benefits do not outweigh risks.
    • Black: Obvious harms, no clear benefits.
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