Diverse Gut Flora Protects Kids from Allergies

LINKÖPING, SwedenHigh diversity and a variety of bacteria in the gut protect children against allergies as opposed to some individual bacterial genera, according to a new study published in the Journal of Allergy and Clinical Immunology.

Researchers at Linköping University conduced at comprehensive study of intestinal microflora in allergic and healthy children. Stool samples from 40 children were analyzed20 children with atopic eczema and allergic IgE antibodies to foods, and another 20 in a control group that lacked these conditions. Using the so-called 454-pyrosequencing, the researchers identified DNA sequences that were then simultaneously linked with a database to determine which bacterial genera was present in the samples.

Results show that diversity was significantly greater in the healthy children at one month of age compared to those children who later developed allergies. Diversity in certain groups appears to be particularly important: Proteobacteria consists of so-called gram-negative bacteria which are associated with protection against allergies and are common in children who grew up on livestock farms with cattle, and even Bacteroides which as shown in the experiments counteract inflammation.

We conducted the study in collaboration with Karolinska Institute and the KTH Royal Institute of Technology that substantiates the so-called hygiene hypothesis. Children acquire intestinal microflora from their environment, and in our society they are probably exposed to insufficient bacteria that are necessary for the immune system to mature," they said.

The findings seem to discredit results of other studies. For example, Bifidobacteria was abundant in the study however the researchers could not identify support for any protective effect.

They concluded the composition of intestinal microflora during the first weeks of life are critical to the immune system's development. In the absence of sufficient stimuli from many different bacteria, the system may overreact against harmless antigens in the environment, such as foods. The risk of developing asthma at school age for children afflicted by these allergies is five to six times higher.