Researchers at Deakin University in Australia have found that certain bacteria present in a mother’s gut during pregnancy can protect their baby from developing food allergies within their first year of life.
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The study, published in Nature Communications on March 24, 2020, furthers the discovery that the Prevotella copri bacterium, which ferments fiber in the diet into fatty acids, was linked to reduced allergic reactions in the offspring of mice that had been fed a high-fiber diet.
Mice are often used in research due to their genomic similarity to humans, and some specific DNA sequence differences associated with human diseases can also be found in mice.
The study states:
“In mice, the maternal microbiome influences fetal immune development and postnatal allergic outcomes. Westernized populations have high rates of allergic disease and low rates of gastrointestinal carriage of Prevotella.”
P. copri is described as a “commensal bacterial genus” that produces short chain fatty acids that could encourage the development of immune tolerances in fetuses.
Peter Vuillermin and his colleagues analyzed data from an Australian study including data from mothers and infants collected between 2010 and 2015. The study involved the collection of fecal samples from the mothers at week 36 of pregnancy, and then from their children one, six, and 12 months old.
These fecal samples were then used to collect DNA from the children who had been diagnosed with a food allergy to then be compared with children without food allergies. From this cohort, 58 children were diagnosed with food allergies, and 236 were not.
Vuillermin suggests that P. copri may even be able to protect children against other allergies like hay fever, which is made even more likely by the fact that food allergies can increase the risk of other types of allergies too.
The researchers found that approximately 20 percent of children without food allergies had Prevotella copri present in their fecal samples. Only 8 percent of children with allergies to egg, peanut and cow’s milk, among other allergens, had P. copri in their fecal samples.
Further analysis showed that the amount of P. copri in the mother’s fecal samples was linked to decreased risks of allergies in her child. There was just one mother with a child diagnosed with food allergies that had over 0.03 percent of P. copri in her fecal sample. When mothers had twice as much P. copri as another, there was an 8 percent decrease in food allergy risk in their children. This was determined by the expression of a particular P. copri gene in their fecal samples.
Environmental factors such as large households could influence the amount of P. copri in a mother’s microbiome (the community of organisms including bacteria, fungi, and viruses that live in the human body). This could be due to the fact that, in larger households, there are more people present to share microbiota with, which is beneficial in terms of boosting the diversity of organisms in the microbiome.
In 1989, David Strachan, an American immunologist, proposed the so-called “hygiene hypothesis” that suggests “family size and position in the household in childhood” were strong influencers in the development of hay fever in particular.
In his study, Strachan went on to conclude that a decreasing family size, “improvements in household amenities, and higher standards of personal cleanliness have reduced the opportunity for cross infection in young families”, which may have resulted in larger clinical expressions of non-food allergies like hay fever.
In Western countries, smaller households and the use of antibiotics means that P. copri is less abundant, although there are a range of factors that influence the bacteria’s presence. Additional studies into the prevalence of Prevotella copri have found that Prevotella strains are associated with plant-rich diets, which are common in non-Western cultures, and vegetarian and Mediterranean diets.
“Our findings have clear implications for public health, given the burden of allergic disease. […] Consequently, if we assume causality, the estimated population-attributable risk of absence of maternal carriage of P. copri for food allergy is greater than 50 percent.”
Peter Vuillermin, Deakin University
Further studies are necessary to replicate the findings of the study in other populations and to determine the mechanisms driving the protection against allergy development and to investigate P. copri’s potential to be used as a probiotic or biomarker.
Ley, R. Prevotella in the Gut: choose carefully. Nat Rev Gastroenterol Hepatol. 2016;13:69-70. https://www.nature.com/articles/nrgastro.2016.4
Li, G. The Bacteria in a Mother’s Gut May Protect Babies from Food Allergies. New Scientist. (2020). https://www.newscientist.com/article/2238421-the-bacteria-in-a-mothers-gut-may-protect-babies-from-food-allergies/#
Strachan, D. Hay fever, Hygiene, and Household Size. BMJ. 1989;299(6710):1259–1260. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC1838109/?page=2
Vuillermin, P. et al. Maternal Carriage of Prevotella During Pregnancy Associates with Protection Against Food Allergy in the Offspring. Nature Community. 2020;11:1452. https://www.nature.com/articles/s41467-020-14552-1