Share on Pinterest
Playing outside or interacting with mud and dirt may affect a child’s microbiome. RyanJLane / Getty Images
  • Researchers from Finland set out to test how adding natural elements to playgrounds could affect children’s immune systems and microbiomes.
  • Early findings suggest that changing children’s environments could be a relatively simple way to boost their immune systems.
  • Experts say more research is needed to understand long-term health effects.

Wondering how to strengthen your kid’s immune system ahead of cold and flu season?

The answer might be as simple as letting them play in the dirt.

A new study found that kids at day cares developed more diverse microbiomes and had less inflammatory immune systems when nature was brought into their playgrounds.

While the long-term health benefits of switching to natural play environments remain to be seen, these early findings suggest that changing children’s environments could be a relatively simple way to boost their immune systems.

They also build upon earlier research that has found other health benefits from playing outside.

In a study published Oct. 14 in the journal Science Advances, researchers from Finland set out to test how adding natural elements to playgrounds could affect children’s immune systems and microbiomes.

They studied 75 kids at 10 day care centers in two cities in Finland. They had six control facilities: Half were nature-oriented day cares, and the other half were standard urban day cares.

The remaining four “intervention” day cares, which originally had little to no natural elements, received a green makeover for the study.

The researchers covered parts of the gravel play yards with forest floor and sod, along with planters for growing annuals and peat blocks that kids could dig into and climb on.

Kids spent an average of 90 minutes outside at their day care each day over the 28-day study, after which researchers swabbed their skin and tested their blood.

The results showed that children from the intervention day cares experienced a higher ratio of anti-inflammatory immune system proteins to pro-inflammatory proteins, which resembled what was found in kids at the nature-oriented day cares, along with a higher diversity of microorganisms on their skin.

The study helps advance scientific understanding of how the environment affects the immune response and microbiome.

It was a major test for the “biodiversity hypothesis,” which states that interacting with natural environments enriches the human microbiome, helps balance the immune system, and ultimately gives people greater protection from allergies and inflammatory diseases.

It has some experts, such as Dr. Martin J. Blaser, professor at the Rutgers Robert Wood Johnson Medical School, Henry Rutgers chair of the human microbiome, and director at the Center for Advanced Biotechnology and Medicine, to take a second look at the hypothesis.

His work focuses on an alternative explanation for the changing microbiome, called the “disappearing microbiota hypothesis,” which says that beneficial microbes that have coevolved with humans are going away as a result of modern life and certain medications (like antibiotics), among other factors.

“The human bacteria that we’re losing are really important, and the environmental [causes] are on the short end of the stick. This paper says that maybe the shorter end of the stick is longer than I thought, and I think it’s a really interesting paper,” he explained.

However, he questions whether the microbes in nature can actually be beneficial to humans, despite their interactions with our immune systems.

“The microbes that live in soil are adapted for soil, and the microbes in pet dogs are adapted to pet dogs, not humans. Many times, when such microbes are introduced in humans, they don’t last that long,” Blaser said.

Researchers say the findings indicate that playing in forest dirt can stimulate pathways that regulate the immune system, but more research is needed to understand whether these children are actually healthier in the long run.

Whether that helps a person’s immune system fight off infections and diseases throughout their life remains to be seen, says Dr. Purna C. Kashyap, a gastroenterologist and co-director of the Mayo Clinic’s microbiome program.

“It may lead to lower diseases, but that’s not an easy extrapolation to make,” he said. “The challenge with these kinds of studies is that you need 10-, 20-, 30-year follow-ups to see how these children do in the long term, rather than just the short term.”

While we wait for longitudinal studies on biodiversity exposure and the immune system to come out, it may still be worth encouraging kids to spend time in nature.

Earlier research does show that playing outside can provide health benefits to children, including lower body mass index (BMI) scores and reduced risk of some vision problems. Plus, it’s just plain fun.

If you’re going to bring your kid to a public park or recreational facility for some time in nature during the pandemic, here are some tips from the Centers for Disease Control and Prevention (CDC) on staying safe:

  • Visit parks close to home.
  • Avoid going during crowded times.
  • Wear a mask.
  • Wash hands frequently and avoid sharing toys and other items.
  • Follow physical distancing guidelines and stay at least 6 feet apart from others outside your household.