A research article written by Marja Roslund, Anirudra Parajuli, Nan Hui, Riikka Puhakka et al. has been published in Ecotoxicology and Environmental Safety. The study is based on the bioversity hypothesis of immune-mediated diseases, which claims that lack of microbiological diversity in the everyday living environment is a core reason for dysregulation of immune tolerance and – eventually – the epidemic of immune-mediated diseases in western urban populations. In this study, the researchers performed the first placebo-controlled double-blinded test that investigates the effect of biodiversity on immune tolerance. In the intervention group, children aged 3–5 years were exposed to playground sand enriched with microbially diverse soil, or in the placebo group, visually similar, but microbially poor sand colored with peat. Sand, skin and gut bacterial, and blood samples were taken at baseline and after 14 days. Bacterial changes were followed for 28 days.
The results showed that bacterial richness and diversity were higher in the intervention than placebo sand. Skin bacterial community, including Gammaproteobacteria, shifted only in the intervention treatment to resemble the bacterial community in the enriched sand. Mean change in plasma interleukin-10 (IL-10) concentration and IL-10 to IL-17A ratio supported immunoregulation in the intervention treatment compared to the placebo treatment. IL-10 levels and IL-10 to IL-17A ratio were associated with Gammaproteobacterial community on the skin. After 28 days, skin bacterial community still differed in the intervention treatment compared to baseline. The findings support the biodiversity hypothesis of immune-mediated diseases. The authors conclude that environmental microbiota may contribute to child health, and that adding microbiological diversity to everyday living environment may support immunoregulation.
Ecotoxicology and Environmental Safety: A Placebo-controlled double-blinded test of the biodiversity hypothesis of immune-mediated diseases: Environmental microbial diversity elicits changes in cytokines and increase in T regulatory cells in young children