Prebiotics for the prevention of allergies: A systematic review and meta-analysis of randomized controlled trials

Background: Prevalence of allergic diseases in infants is approximately 10% reaching 20 to 30% in those with an allergic first-degree relative. Prebiotics are selectively fermented food ingredients that allow specific changes in composition/activity of the gastrointestinal microflora. They modulate immune responses, and their supplementation has been proposed as an intervention to prevent allergies. Objective: To assess in pregnant women, breastfeeding mothers, and infants (populations) the effect of supplementing prebiotics (intervention) versus no prebiotics (comparison) on the development of allergic diseases and to inform the World Allergy Organization guidelines. Methods: We performed a systematic review of studies assessing the effects of prebiotic supplementation with an intention to prevent the development of allergies. Results: Of 446 unique records published until November 2016 in Cochrane, MEDLINE, and EMBASE, 22 studies fulfilled a priori specified criteria. We did not find any studies of prebiotics given to pregnant women or breastfeeding mothers. Prebiotic supplementation in infants, compared to placebo, had the following effects: risk of developing eczema (RR: 0.68, 95% CI: 0.40 to 1.15), wheezing/asthma (RR, 0.37; 95% CI: 0.17 to 0.80), and food allergy (RR: 0.28, 95% CI: 0.08 to 1.00). There was no evidence of an increased risk of any adverse effects (RR: 1.01, 95% CI: 0.92 to 1.10). Prebiotic supplementation had little influence growth rate (MD: 0.92 g per day faster with prebiotics, 95% CI: 0 to 1.84) and the final infant weight (MD: 0.10 kg higher with prebiotics, 95% CI: -0.09 to 0.29). The certainty of these estimates is very low due to risk of bias and imprecision of the results. Conclusions: Currently available evidence on prebiotic supplementation to reduce the risk of developing allergies is very uncertain.