Moving from theory to practice with probiotics has been problematic in many areas. That is, theoretically probiotics by altering the microbiome should have numerous beneficial effects; however, demonstrating these positive effects in practice has been difficult for many conditions. A recent study (thanks to Mike Hart for this reference) highlights this issue with regard to asthma: Pediatrics 2013; 132: e666-76. Full article:
Background: Due to the immune modulating effects of probiotics and mindful of the hygiene hypothesis regarding the rise of atopic diseases, some have proposed the use of probiotics to reduce the risk of atopy and asthma in children.
Methods: In this study, the authors performed a meta-analysis of numerous randomized studies. Out of a total of 1081 articles, 25 studies met predefined criteria, with a total of 4031 participants (see Table 1 in publication). Numerous probiotics were administered. The most common probiotic in these trials, Lactobacillus GG, was used in 8 of the studies.
- For serum immunoglobulin E (IgE) levels, 9 of the trials (n=1103) provided data. Probiotics were associated with a -7.59 U/mL reduction in total IgE (P= .044). The effect of probiotics was more pronounced with longer, follow-up periods.
- Probiotics, in comparison to placebo, were associated with a reduced risk of atopic sensitization based on positive skin prick and/or elevated specific IgE to common allergens. This was true whether the probiotic was administered prenatally (relative risk 0.88, P=.035) or postnatally (relative risk 0.86, P=.027)
- Probiotics did not reduce the risk of asthma/wheeze (relative risk 0.96 [95% CI 0.85-1.07]
Study limitations: heterogeneity of clinical trials in meta-analysis, various probiotic strains, variable duration and timing of probiotic use.
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