Adding biodiverse elements to a play yard can enhance preschoolers' immune systems

Roslund, M. ., Puhakka, R. ., Grönroos, M. ., Nurminen, N. ., Oikarinen, S. ., Gazali, A. ., … Laitinen, O. . (2020). Biodiversity intervention enhances immune regulation and health-associated commensal microbiota among daycare children. Science Advances, 6. https://doi.org/http://dx.doi.org/10.1126/sciadv.aba2578

The incidence of immune-mediated diseases has increased rapidly in many societies around the world, especially in modern urban communities. One possible explanation for this increase relates to a decrease in environmental biodiversity in those communities and an associated microbial imbalance in humans. This imbalance, referred to as dysbiosis, is associated with immune-mediated diseases. While this explanation is widely accepted, conclusive evidence in support of the belief is still lacking. This study sought to fill this gap by manipulating urban environmental biodiversity and then examining its effect on changes in the skin and gut microbiota and blood immune markers of preschool children.

Researchers enriched the environmental biodiversity of four urban daycare centers in Finland by covering their yards with forest floor and sod. These centers served as “intervention” cites for the study. Six other daycare centers participated in the study: three had standard yards (no biodiverse elements added); three were nature-oriented centers where children made daily visits to a nearby forest. Children in the intervention and standard daycare centers spent approximately 1.5 hours per day in their yards. Assessments completed on 75 children (age 3-5) from the participating daycare centers measured skin and gut microbiota, and two blood immune markers before and after a 28-day intervention period. Measures of environmental microbiota were also conducted on the standard and intervention daycare yards.

After the intervention, the total bacterial community differed between intervention and standard daycare yards, with the intervention yard showing considerably more soil microbiota than the standard yard. One specific class of bacteria, Gammaproteobacteria, was over eight times higher in the intervention yards than the standard daycare yards. After the intervention, children in the intervention daycare showed higher diversity of skin Proteobacteria and Gammaproteobacterial communities than children in the standard daycare. Prior to the intervention, these two groups had similar bacterial community composition and hosted equally diverse skin Proteobacterial communities. After the intervention, the skin and intestinal microbiota of children with the “intervention” yard was similar to the microbiota of children visiting the forest every day. The children attending the daycare with the standard yard, however, showed a decline in the diversity of their microbiota. Post-intervention readings of blood immune markers of children in the intervention daycare suggested that the intervention may have stimulated immunoregulatory pathways and thus enhanced the children's immune system.

The overall results showed that adding biodiversity elements to daycare yards diversified both the environmental and skin microbiota and made positive changes to children's immune functioning. The findings of this experimental study support the belief that the lack of biodiversity in the environment can place people at greater risk for of immune-mediated diseases. The findings also indicate that transforming standard playgrounds with inorganic surfaces to rich biodiverse environments can help boost children's immune systems.

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