Data from 1,879 American adults indicated that the fecal microbiota of people with allergies was very different from people without allergies and they also had markedly fewer species.
“American adults with allergies, especially but not exclusively to nuts and seasonal pollen, have lower richness and altered composition of their gut microbiota,” wrote the scientists from the National Cancer Institute at the National Institutes of Health in the journal EBioMedicine.
“This observation of an allergy-associated dysbiosis supports the hygiene hypothesis, but the origin of the dysbiosis is unknown. Also unknown is whether prevention or amelioration of the dysbiosis can modify allergy prevalence or severity.
“Clinical trials and other longitudinal studies that incorporate fecal microbiota characterization will be needed to address these questions.”
“New clues to define microbiota deviations”
In an accompanying commentary in EBioMedicine, Dr Seppo Salminen, Director of the Functional Foods Forum at the University of Turku in Finland, said that the data provides, “interesting cross-sectional associations between the gut microbiota and allergic symptoms. However, the presence of an altered microbiota in the gut associated with allergy or intolerance symptoms cannot be considered as a cause or even an effect as the questions related to the association with microbiota composition are likely to be overestimated and in some cases even untrue.
“However, the study provides new clues to define microbiota deviations, which could serve as markers of increased risk or treatment success in adult subjects who suffer from allergic diseases of intestinal origin.
“Allergic participants also had markedly altered microbiota composition and the results were especially significant in the case of subjects with nut and seasonal allergies. Thus, the results are in concordance with allergy-associated gut microbiota deviations and they are consistent with the hygiene hypothesis. These results may provide clues to devising treatment or prevention strategies for allergic disease in adults. However, more work is needed on potential markers which could support prevention strategies also in infants and children.”
Led by James Goedert, the researchers assessed data from 1,879 people in the American Gut Project. Almost 82% of the participants reported some form of allergy, with about 3% suffering from allergies from peanuts, tree nuts, or shellfish; and 9% reported other food allergies. The most common allergies were seasonal with 40% of people having these allergies.
The data indicated an association between the diversity of the fecal microbiota and allergy, with people with allergies found to have lower microbiota diversity.
All of the different types of allergy were associated with a reduced microbiota richness, except asthma, bee sting, and eczema.
“The dysbiosis was most marked with allergies to nuts and seasonal pollen, and it was driven by higher abundance of Bacteroidales and reduced abundance of Clostridiales,” wrote the scientists.
Commenting on the potential origins of these associations, the scientists note that cesarean birth is a possibility. Several studies have reported that cesarean delivery can delay colonization by specific bacteria and can impact the developing immune system of the infants.
“In a Danish study based on 16S rRNA fingerprinting, lower fecal bacterial diversity at age 1 month was not associated with cesarean delivery, but it was associated with increased likelihood of allergic rhinitis (1.3-fold) by age 6 years (Bisgaard et al., 2011, J. Allergy Clin. Immunol., Vol. 128, pp. 646–652),” wrote the researchers.
“Consistent with the Danish study, allergy was not associated with cesarean birth in the current study. Moreover, although we found that both cesarean birth and allergies were associated with low richness, they were associated with different taxa (Goedert et al., 2014, EBioMedicine, Vol. 1, pp. 167–172).
“These findings suggest that the dysbiosis of allergy in adults develops postnatally.”
Published online ahead of print, doi: 10.1016/j.ebiom.2015.11.038
“Allergy associations with the adult fecal microbiota: Analysis of the American Gut Project”
Authors: X. Hua, J.J. Goedert, A. Pu, G. Yu, J. Shi
Published online ahead of print, doi: 10.1016/j.ebiom.2015.11.051
“Allergy Associations with the Adult Fecal Microbiota: Cause, Effect or Biomarker?”
Author: S. Salminen