If you haven't heard of it already, food allergies are on the rise. They affect as much as 10% of the population, in some parts of the world. (1) There has also been a sharp increase in their prevalence over the last few decades. (2)
One hypothesis suggests that twenty-first-century lifestyle choices are a contributing factor. These include the misuse of antibiotics, dietary shifts and the mode of birth. These lifestyle choices can alter bacterial communities in the gut. And this leads to an increased susceptibility to food allergies. (3)
There are many symptoms of food allergies. Some of them are minor such as puffy eyelids and upset stomachs. But some of them are serious such as anaphylactic shocks and the inability to breathe from a swollen windpipe. These effects can greatly influence the quality of life. Needless to say, they cause both physiological symptoms. psychological symptoms and distress.
Food allergies and the Gut Microbiome
Milk is the second most common allergen in several countries across the world. A study showed that microbes found in the gut of infants with a milk allergy were different from those found in healthy infants. It was also found that mice who were treated with antibiotics or lacked certain microbes were more sensitive to food allergies. (4)
This triggered the question: Could microbes from healthy infants play a protective role in those with milk allergies?
A joint study was conducted by researchers from three different universities. These were from the University of Chicago, University of Naples Federico II, Italy and Argonne National Laboratory University. The aim of the study was to understand the role of gut microbes in regulating human food allergies.
The mice were divided into two groups. One group which had a milk allergy and another was their healthy counterpart. Faecal samples from infant mice of both these groups were used to colonize germ-free mice.
The mice were kept in a sterile, germ-free environment to ensure they had no bacteria of their own. The mice were fed the same food as the infants to ensure that the same nutrients were available to the colonizing bacteria. Then, the germ-free mice were divided into 3 groups. One which was colonized by the bacteria of allergic infants, another colonized by bacteria from healthy infants. And the third group of mice which was not colonized at all. All these 3 groups were introduced to milk for the first time to observe their responses.
It was found that mice colonized with bacteria from allergic infants showed a strong reaction. They had a powerful anaphylactic shock which was potentially life-threatening. Germ-free mice that had not been colonized with any bacteria also experienced the same reaction. The odd group out was the mice that have been colonized with bacteria from healthy infants. They suffered from no anaphylactic reaction at all.
The gut microbes of each of these groups were different from one another. When a further investigation was done on all these three groups a very interesting phenomenon was observed. It was found that the bacteria in the gut of these mice influenced the expression of different genes.
It goes on to show that the microbial composition affects gene expression and in turn immunity. Further investigation helped identify the single species responsible for this effect, Anaerostipes caccae. Even when this species was used in isolation, it played a protective role and prevented the onset of milk allergy in developing mice. (5)
Implications for food allergy research and management
Canani, one of the researchers, mentioned how these findings demonstrate the critical role of gut microbiota. Particularly so with the development of food allergy. And suggested that modulating bacterial communities could be used to tackle food allergies. Another researcher, Naler, mentioned further implications of the study. He mentioned how metabolic products from a healthy gut could help in the development of drugs against food allergies. This opens up the door for further research into using microbes to modify gut bacterial communities.
The food we eat plays a very critical role in deciding the kind of bacteria that resides in our guts. Any change in the food we eat affects these microbes. Discover what YOUR gut microbiome looks like and order your Viome Gut Intelligence Test now!
1. Loh, W., & Tang, M. . The Epidemiology of Food Allergy in the Global Context. International journal of environmental research and public health, 15(9), 2043. (2018)
2. Stea, A. T. et al. Commensal bacteria protect against food allergen sensitization. Proc. Natl Acad. Sci. USA 111, 13145–13150 (2014).
3. Wesemann, D. R. & Nagler, C. R. e microbiome, timing, and barrier function in the context of allergic disease. Immunity 44, 728–738 (2016).
4. Bunyavanich, S. et al. Early-life gut microbiome composition and milk allergy resolution. J. Allergy Clin. Immunol. 138, 1122–1130 (2016).
5. T Feehley et al. Healthy infants harbor intestinal bacteria that protect against food allergy. Nature Medicine DOI: 10.1038/s41591-018-0324-z (2019).