Probiotics May Protect Infants From Allergy, but Not Asthma

Larry Hand

August 19, 2013

Prenatal and postnatal administration of probiotics may reduce immunoglobulin E (IgE) levels in infants and protect against sensitization to hereditary allergies but may not protect against asthma or wheezing, according to a new meta-analysis.

Nancy Elazab, MD, from the Division of Pediatric Pulmonology, University of Miami, Florida, and colleagues reported their results in an article published online August 19 and in the September issue of Pediatrics.

The investigators reviewed 1081 randomized controlled trials published between 2001 and 2012. They identified 25 studies (4031 participants) for inclusion in a meta-analysis to assess probiotic effect against atopy and asthma in infants compared with placebo.

Overall, probiotics reduced total IgE levels (weighted mean difference [WMD], −7.59 U/mL; 95% confidence interval [CI], −14.96 to −0.22; P = .044). The effect was significant among children with atopy (WMD, −35.12 U/mL; 95% CI, −69.82 to −0.42; P = .047), but not among nonatopic children with family history. When the investigators analyzed subgroups by age, they found that the effect of probiotics on IgE levels was significant among children 2 years old and older (WMD, −12.74 U/mL; 95% CI, −24.55 to −0.93; P = .035).

The protective effect of probiotics was also more pronounced with longer follow-up times, based on multivariate meta-regression analyses including baseline age, age at follow-up, sex, treatment length, daily and total dose, and duration of follow-up.

Overall, probiotics showed a trend toward reducing the risk of atopic sensitization, defined as positive skin prick test and/or elevated specific IgE (relative risk [RR], 0.90; 95% CI, 0.80 - 1.00; P = .060). However, timing of the probiotics made a difference. Prenatally and postnatally administered probiotics significantly reduced the risk for atopy overall (RR, 0.88; 95% CI, 0.78 - 0.99; P = .035), but postnatal-only probiotics fell short of significance.

In addition, a subgroup analysis of probiotics showed that prenatally and postnatally administered probiotics significantly reduced the risk for common allergens on the basis of a positive skin prick test (RR, 0.86; 95% CI, 0.75 - 0.98; P = .027).

In multivariate meta-regression analysis, Lactobacillus acidophilus showed an association with increased risk for atopic sensitization (β, 0.45; 95% CI, 0.16 - 0.74; PP = .002).

Probiotics, however, did not significantly reduce the risk for asthma and wheezing. The researchers speculate that this lack of effect may have been a result of specific combinations of strains or insufficient length of follow-up.

The researchers conclude, "[C]arefully selected probiotics administered during pregnancy and early infancy may have a role in the primary prevention of atopic diseases, particularly in high-risk infants."

The authors have disclosed no relevant financial relationships.

Pediatrics. Published online August 19, 2013.

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