The composition of the gut flora of infants when they switch from liquids to solids affects the development of allergies. This finding comes from the PhD research of Harm Wopereis in the Laboratory of Microbiology.
In healthy babies who are breastfed, the intestinal microbiome (commonly known as gut flora) largely consists of Bifidobacteria in the first few months. That creates an acidic intestinal environment. Once the baby moves onto solids, the population becomes more diverse and gradually starts to look like the microbiome of an adult.
Breast milk contains indigestible sugars that serve as food for the Bifidobacteria. That is why a lot of infant formula has for the past 20 years contained fibres aimed at encouraging Bifidobacteria in the intestines. These so-called prebiotics are also combined with live Bifidobacteria (probiotics). Wopereis investigated the effects of prebiotics and synbiotics (prebiotics plus probiotics) on the intestinal microbiomes of children with a predisposition to allergy or who were allergic to cow’s milk.
He found that adding prebiotics and synbiotics creates an intestinal microbiome that is closer to that of children who are breastfed. He also discovered that a strongly acidic intestinal environment is good for the bacteria that follow the Bifidobacteria, which convert the acids into butyrate. These bacteria — including the genera Anaerostipes and Eubacterium — may also provide protection against eczema. ‘These groups of bacteria were less prevalent in children who developed eczema during the shift to solids,’ says Wopereis. The transition to more diverse gut flora also went less well in this group.
In experiments with faecal transplants in mice, Wopereis demonstrated that the bifidogenic environment is indeed a determining factor in the protection against allergies. The IgE level increased in mice that were given poo from children with an allergy to cow’s milk. ‘That level is the most important immune factor in allergic reactions.’