A probiotic formula given to infants who are allergic to cow's milk changes the composition of their gut bacteria to help them develop tolerance to the food, according to a new study.
The discovery of bacteria that drive tolerance to problem foods like cow's milk could be crucial to developing new treatments to help children with food allergies, researchers said.
Allergy to cow's milk is one of the most common food allergies in developed countries, occurring in up to three per cent of children worldwide.
Emerging evidence suggests that modern environmental influences, including widespread antibiotic use, high-fat and low-fibre diets, reduced exposure to infectious diseases, Caesarean birth and formula feeding have altered the mutually beneficial relationship between humans and the bacteria that live in our gastrointestinal tract.
This dysbiosis, or skewing of the structure of the microbial community, can predispose genetically susceptible individuals to allergies.
Previous research has shown that infants with cow's milk allergy who are fed formula containing a form of the milk protein casein, supplemented with the probiotic bacterial species Lactobacillus rhamnosus GG (LGG), develop tolerance at higher rates than those treated with a non-probiotic formula.
"Mouse model work from our laboratory published last year identified a common class of mucus-associated gut bacteria that play a critical role in regulating the access of dietary allergens to the bloodstream," said lead author Cathryn Nagler, professor at the University of Chicago.
"This suggests a novel mechanism by which commensal bacteria regulate allergic responses to food," Nagler said.
Researchers examined whether probiotic administration modulates gut bacterial composition to enhance acquisition of tolerance to cow's milk.
They performed sequence analysis to identify bacteria in stool samples collected from healthy infant subjects, infants with cow's milk allergy who had been fed the LGG enriched probiotic formula, and those who had been fed the formula without added probiotics.
Overall, the gut microbiome of infants with a cow's milk allergy was significantly different than healthy controls, suggesting that differences in the structure of the bacterial community indeed influence the development of allergies.
Infants treated with the LGG probiotic formula who developed tolerance to cow's milk also had higher levels of bacteria that produce butyrate than those who were fed the probiotic formula but did not develop tolerance.
This further suggests that tolerance is linked to the acquisition of specific strains of bacteria, including Blautia and Coprococcus, which produce butyrate.
"The ability to identify bacterial strains that could be used as novel therapeutics for treating food allergies is a fundamental advance," said co-author Jack Gilbert, associate professor at the University of Chicago.
