A new study published in the journal Pediatrics suggests that taking probiotics during pregnancy or early in life may reduce the risk of developing food allergies.
By reviewing and analyzing 25 past studies, researchers from four universities across the United States found that pre-natal or early-life consumption of probiotics reduced the risk of developing allergies, and also reduced the total level of the antibody that plays a central role in anaphylaxis: immunoglobulin E, or IgE.
With regard to total IgE level, no difference was observed between mothers who only gave probiotics to their baby early in life versus those who took probiotics during pregnancy as well: in either case, total IgE was reduced.
However, the opposite was true for allergic sensitization (defined as a positive skin-prick test, or elevated specific-IgE to any food or airborne allergen): in order for the protective effect to be observed, probiotics had to be taken both during the mother’s pregnancy and the early life of the child.
This study  adds to a growing body of research which suggests that bacteria which live inside us (which outnumber our own cells by 10-to-one) play an integral role in the body, including in the development of the immune system. Differences in these bacteria may affect not only the onset of allergic disease, but many other disorders as well.
Numerous studies have associated differences in the amount or diversity of bacteria in the intestines with food allergies and eczema. Probiotics are essentially a supplement of bacteria; they work by introducing bacteria into the body, and can contain a number of different bacterial strains.
However, this doesn’t mean it’s time to head to the supplement aisle and start stocking up on bottles of bacteria: some past studies have had contradictory results, finding either that probiotics had no effect, or even made allergy more likely. This study’s authors say this probably has to do with the strains chosen: different studies use different strains of bacteria, and there is no consensus yet on which strains would be the “best,” or which combinations of strains. For example, in this study, one strain popularly used in supplements (Lactobacillus acidophilus) was found to actually increase the risk of allergic sensitization when compared with other strains.
In all cases, consuming probiotics did not appear to significantly reduce asthma or wheeze. Further studies are required to determine why this was found; the authors note it could be related to the probiotic strain and/or follow-up duration.
The authors conclude that “carefully selected probiotics administered during pregnancy and early infancy may have a role in the primary prevention of atopic disease, particularly in high-risk infants.”