Probiotics are live microorganisms intended to boost health, such as the bacteria in some yogurts. These are popular among the health conscious. One of probiotics' most popular uses is in preventing and treating digestive problems.
Susanne Hempel, from RAND Health in Santa Monica, Calif., and colleagues conducted a systematic literature review using searches of 12 electronic databases and a meta-analysis of 82 randomized controlled trials (RCTs) of probiotics (Lactobacillus, Bifidobacterium, Saccharomyces, Streptococcus, Enterococcus, and/or Bacillus). In the meta-analysis researchers find that probiotics have potential in alleviating the diarrhoea that afflicts about one-third of people treated with antibiotic medications (Antibiotic associated diarrhoea – AAD). Diarrhoea is more common with certain antibiotics, particularly at high doses needed to treat serious infections. Probiotics reduced the risk of antibiotic-associated diarrhoea by 42%, according to the analysis in today's Journal of the American Medical Association.
According to study co-author Sydne Newberry, a nutritionist and researcher for the Southern California Evidence-Based Practice Center at the Rand Corp. in Santa Monica, this study provides specific guidance to patients or their doctors.
The studies she reviewed didn't provide enough details — such as the specific strain of bacteria — for consumers to know exactly what to take and how often, Newberry said. Scientists need to conduct much more targeted clinical trials, testing particular doses of individual probiotics against one another, to give patients and their doctors better guidance, she explained.
The researchers found that the majority of included studies used Lactobacillus-based interventions alone or in combination with other genera and that strains were poorly documented. The pooled relative risk of 63 RCTs that included 11,811 participants indicated a statistically significant association between probiotic administration and reduction in AAD (relative risk, 0.58; 95 percent confidence interval, 0.50 to 0.68; number needed to treat, 13). This result was relatively insensitive to subgroup analyses. The evidence is insufficient to identify if this association varies systematically by population, antibiotic characteristic, or probiotic preparation. “The pooled evidence suggests that probiotics are associated with a reduction in AAD. More research is needed to determine which probiotics are associated with the greatest efficacy and for which patients receiving which specific antibiotics,” the authors write.
But the study underscores the importance of maintaining a proper balance of microbes in the digestive tract, said Roshini Rajapaksa, a gastroenterologist at the NYU Langone Medical Center who wasn't involved in the study. When people take antibiotics, the drugs kill not only the bad bacteria that cause illness but also the good microbes that help regulate the intestines, she said.
In the meantime, people should be careful about what they buy, especially when when considering probiotics for children, warned David Bernstein, chief of hepatology at North Shore University Hospital in Manhasset, N.Y.
Though foods such as yogurts are safe, probiotics could pose risks for children with weak immune systems, those who are chronically debilitated or those who are seriously ill, the American Academy of Pediatrics says. In rare cases, probiotics are associated with dangerous bloodstream infections. Dietary supplements such as probiotics are not approved by the government for safety and effectiveness before they are marketed, the Food and Drug Administration says.
Global sales of probiotic foods and supplements reached $21 billion in 2010 and were projected to reach $31 billion by 2015, according to one market analysis.
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