Probiotic Drink May Not Prevent Antibiotic-Associated Diarrhea

Laurie Barclay, MD

August 17, 2009

August 18, 2009 — Kefir, a fermented milk product similar to yogurt but containing different fermentation microbes, may not prevent antibiotic-associated diarrhea, according to the results of a double-blinded, randomized, allocation concealment clinical trial reported in the August issue of the Archives of Pediatric and Adolescent Medicine.

"The promise of using functional foods to mitigate disease and promote health is one of the major reasons so many resources are being placed in this exciting new field," write Daniel J. Merenstein, MD, from Georgetown University Medical Center in Washington, DC, and colleagues from the Measuring the Influence of Kefir (MILK) Study. "Kefir grains constitute both lactose-fermenting yeasts (Kluyveromyces marxianus) and non–lactose-fermenting yeasts (Saccharomyces unisporus, Saccharomyces cerevisiae, and Saccharomyces exiguus). It is believed that these probiotics deliver beneficial bacteria to the gut, improving gastrointestinal health, and may protect against [antibiotic-associated diarrhea]."

The goal of this study was to evaluate the effect of a commercially available kefir product (Probugs, Lifeway Foods, Inc) on the prevention of antibiotic-associated diarrhea among 125 children aged 1 to 5 years and presenting to primary care clinicians in the Washington, DC, metropolitan area. Participants were randomly assigned to receive kefir drink or heat-killed matching placebo, and the main study endpoint was the incidence of diarrhea during the 14-day follow-up period after children were given antibiotics.

Rates of diarrhea did not differ significantly between groups (18% in the kefir group vs 21.9% in the placebo group; relative risk, 0.82; 95% confidence interval, 0.54 – 1.43), nor did secondary outcomes differ between groups. The investigators noted some interesting interactions among initial health at enrollment and participant age and sex, suggesting the need for additional study.

"In our trial, kefir did not prevent [antibiotic-associated diarrhea]," the study authors write. "Further independent research on the potential of kefir needs to be conducted."

Limitations of this study include the lack of stool testing or culture for pathogens, a lack of data regarding the presence of Clostridium difficile, a generally very healthy population, and a reliance on parental reports.

"It is important to recognize that this trial studied specific strains at specific dosages and our findings cannot be extrapolated for other strains or outcomes," the study authors conclude. "There are some intriguing data that we believe deserve further elucidation and may hold promise for kefir's role in [antibiotic-associated diarrhea] prevention. We also believe that it is important that commercial products continue to be independently studied and subjected to high-quality research techniques, as many products appear to present themselves as a panacea while lacking patient-oriented outcome data."

Lifeway Foods, Inc, the maker of Probugs, supported this study and provided study drinks. The study authors have disclosed no relevant financial relationships.

Arch Pediatr Adolesc Med. 2009;163:750–754.

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