Gaby
A team from the University of Helsinki enrolled 75 toddlers, ages 3 to 5, from 10 preschools in the Finnish capital for the experiment. The researchers found that just one month of play on a simulated forest floor and among greenery was enough to boost the children’s immune systems.
How the Study Was Conducted
The scientists asked preschool staff to create special research lawns by planting moss and typical forest shrubs (including dwarf heather and blueberries) and by placing plant boxes in the schools. Educators were instructed to let the children play on the makeshift forest floor, care for the plants, and dig in the soil to their hearts’ content.
Meanwhile, the researchers systematically analyzed the health of the young participants, paying particular attention to their immune systems. They found that these playful interactions led to rapid improvements in the children’s gut and skin microbiomes.
Compared with other urban children who continued to play on sidewalks, tiles, and gravel during the experiment, the study participants showed an increase in T cells and other important immune markers in their blood after just 28 days.
Even in such a short period, the microbial communities on the skin and in the guts of children who regularly played among greenery became more diverse. That diversity is linked to a healthier immune system.
“We also found that the gut microbiome of children who interacted with greenery was similar to that of children who visit the forest daily,” said ecologist Marja Roslund.
Conclusions Drawn by the Team
Previous studies showed that spending time among greenery correlates with immune health, but until now it wasn’t clear whether the relationship was causal. This current study is the first to establish that link, Science Alert reports.
While the findings don’t answer every question, they support the idea that changes in the microbial composition of the environment can quickly influence children’s microbiomes and, in turn, strengthen their immune systems. Scientists call that the “biodiversity hypothesis,” which suggests that the loss of biodiversity in urban areas may be at least partly responsible for the rise in immune-related diseases.
Contact with nature also appears to help prevent immune disorders such as autoimmune diseases and allergies. Spending time outdoors can also benefit children’s eyesight and mental health.
“It would be great if children could play in puddles and dig in organic soil,” said ecologist Aki Sinkkonen, a co-author of the study. The authors recommend that children spend time in nature at least five times a week to help strengthen their immune systems.
Connecting with nature in childhood also helps future ecosystems: children who frequently spend time outdoors are more likely to become environmental advocates as adults.
The results of the study were published in the journal Science Advances.
