Some time ago, it was a common practice in some countries to bring candy and cakes to celebrate birthdays at school with friends and classmates, and there was no problem. Everyone ate and enjoyed the food, and went home happy with chocolate stains all over their clothes. A generation or two after, that has become an unthinkable tradition for kids. The reason: the recent rise of food allergies.
According to Allergy UK, rates of allergy are rising all over the world, affecting 30 to 35% of people at some stage of their lives. Initially, asthma and allergic rhinitis were the most common problems; but recent studies have shown a significant increase in the incidence of food allergies, especially among infants. In fact, since 1997 there has been an estimated 50% more children suffering from food allergies. The reasons explaining this rise are not clearly known, although some previous studies have hinted that our 21st century lifestyle and diet may play a role.
Cathryn Nagler is a Professor at the University of Chicago, in Illinois. For years, she has been studying whether there is a link between the immune system, the intestinal bacteria and the onset of allergies. In 2004, she found that wiping out gut microbiota in mice led to the onset of food allergies. She has now gone one step further.
In the study, Nagler and her team dosed two groups of mice with peanut allergens. One group, born and raised in a sterile environment, was free of gut germs and the other group had mice treated with antibiotics as newborns (which significantly reduces gut bacteria). The researchers compared those two groups with mice who had healthy gut microbiota populations; they found (as one would expect) higher levels of antibodies against peanut allergens in the bloodstream of these two groups of rodents; this demonstrates effective sensitization.
Next, they gave those mice a solution containing Clostridia, a common bacteria strain found naturally in mammalian guts: surprisingly the rodent’s food allergen sensitization disappeared. Researchers then repeated the experiment with another healthy bacteria, Bacteroides, giving it to mice who were similarly prone to peanut allergies, but the effect was not reproduced. This indicates that the Clostridia strain has a unique, protective role against food allergens.
Researchers believe that Clostridia might act through certain immune cells and help keep peanut proteins that can cause allergic reactions out of the bloodstream. “These bacteria are very abundant and reside very close to the epithelial lining, so they’re in intimate contact with the immune system”, Dr. Nagler explained recently in an interview. “These bacteria are maintaining the integrity of the intestinal barrier”, she adds. Researchers prefer to remain cautious for the time being as the findings can only be applied to the analysed population and the cause-and-effect relationship still has to be studied.
We are happy to hear about these results, which might bring science closer to finding a solution to address an important health issue, such as food allergies.