Up until recently, playing outside was just what kids did. It’s where they created their own games, rules, learned how to interact with other kids. Today, we are experiencing a significant move to an indoor childhood. But that shift doesn’t come without costs. Lost are the many benefits of nature and outdoor play for our kids.
Nature can calm a child, bring out their creativity, lift their mood. Nature play helps them develop more social skills, be more balanced and more fit. But in today’s society in which health is at the forefront of our minds, do you know what else nature play can do? Boost a child’s immune system. You may have heard the expression “dirt is good.” But don’t disregard this as an old wive’s tale or a mother’s intuition. Science backs this up.
A few weeks ago, a recent study caught our eye. In the study, researchers from Finland wanted to see what would happen if you added natural elements to children's playgrounds. Specifically, they wondered if the new natural elements could affect a child’s immune system. The study recruited 75 Finnish kids from 10 daycare centers in two cities in which half were nature-oriented daycares and the other half were standard urban daycares. In addition, four daycares served as “intervention” daycares. These facilities originally had little to no natural elements but received a green makeover for the study.
For the intervention daycares, parts of the gravel play yards were covered with natural elements from the forest floor, as well as sod. They also added planters and peat blocks that kids could dig into and climb on. The researchers ensured that the children spent an average of 90 minutes outside at their daycare each day over the 28-day study, after which researchers swabbed their skin and tested their blood.
After the swabbing was done and the blood analyzed, the researchers found that children from the daycares with added natural play elements had more anti-inflammatory immune system proteins than pro-inflammatory proteins. This result was also seen in the children at the nature-oriented daycares, though not at the traditional daycares. What does this tell us? Well, it suggests that bringing in natural play elements to a daycare setting could be a pretty easy way to boost a child’s immune systems. Of course, this was a short-term study. And most experts would agree that we need to see more results from follow-up studies to see how these children do later in life before we can decide if the immunity boost researchers saw continued to provide benefits.
The Deal on Dirt
But the Finnish nature play study was certainly not the first of its kind. In fact, researchers have been studying the effects of dirt on our health for some time. Jack Gilbert is a scientist who studies microbial ecosystems at the University of Chicago. He is also the co-author of a book called Dirt is Good: The Advantage of Germs for Your Child's Developing Immune System. In his book, Gilbert says that one of the main things parents do wrong is over-sterilizing their environment—keeping their children from ever getting dirty. The result of overzealous sterilization and a ban on dirt is that allergies have become widespread. As he told NPR, “In the past, we would have allowed our children to be exposed to animals and plants and soil on a much more regular basis. Now we live indoors. We sterilize our surfaces. Their immune systems then become hyper-sensitized. You have these little soldier cells in your body called neutrophils, and when they spend too long going around looking for something to do, they become grumpy and pro-inflammatory. And so when they finally see something that's foreign, like a piece of pollen, they become explosively inflammatory. They go crazy. That's what triggers asthma and eczema and often times, food allergies.”
Speaking of the effects of living in sterilized environments, here's another interesting study that got our attention that looked at the benefits of the outdoors on a child's immune system in Amish and Hutterite communities. Both of these communities have very similar ancestry and many similarities in lifestyle, including the fact that both are farming communities. One of the major differences between these communities is how they choose to farm. The Amish practice traditional farming, living on single-family dairy farms, using horses for fieldwork and transportation. While the Hutterites live on large, highly industrialized, communal farms.
What makes the communities interesting to study from an immunity perspective, is the striking difference in their rates of asthma: Just over 5% of Amish have asthma vs. 21.3% for the Hutterite. With remarkable genetic similarities between the two communities, genetics could not explain the asthma rates and so researchers wondered if their different farming practices might explain the striking difference in asthma rates.
So researchers decided to conduct a study with thirty Amish children living in Indiana and thirty Hutterite children living in South Dakota. After taking samples of dust from inside the children’s homes as well as blood samples from the children, they found that endotoxin (or a cell wall component of the outer membrane of Gram-negative bacteria found in house dust) levels were nearly 7 times higher in the Amish homes than in the Hutterite homes. This means that the Amish children were exposed to higher levels of bacteria in their homes than the Hutterite children.
When the scientists examined the blood samples from the two groups of children, they also found significant differences. In essence, vital immune pathways were activated in the Amish children, but not in the Hutterite children. What does all of this mean? It could mean that the less industrial, more natural Amish farming environment which is rich in microorganisms provides a type of protection for the children by activating the immune response. As this study saw, it could offer the children protections against asthma.
To look more deeply at nature play and the benefits of being in nature for a child's immunity, let’s go back to Finland.
After the Second World War, Finland gave up a large swath of territory to the Soviet Union. During the second half of the 20th century, the Finnish communities along the border became modernized, while the communities on the Soviet side maintained a more agrarian, traditional lifestyle.
What is most interesting for our look at the benefits of nature for our immune systems is that by the 21st century, allergies on Finland’s side of the border region were significantly higher than on the Russian side. Researchers thought exposure to microbes in the environment was the most likely reason why. So they took samples from both communities. They found that the less-developed Russian side of the border had a higher abundance of Acinetobacter on their skin than the Finnish side. Acinetobacter is a genus of microbes in the Proteobacteria phylum that are commonly found on plants. Interestingly, the researchers found that children with more Acinetobacter on their skin had more leukocytes in their bloodstream and that these cells were much more capable of producing the anti-inflammatory cytokine IL-10 compared with the leukocytes of urban kids. Hence, a stronger immune system with more bacteria.
To source those microbes to the soil, a team from the University of Helsinki turned to mice. They split up groups of female mice, housing some on clean bedding while their sisters lived in cages sprinkled with potting soil and kept in a stable that housed other animals such as sheep. After six weeks, the clean bedding sisters were found to be more susceptible to developing lung inflammation in response to an asthma-triggering allergen than were the mice in contact with soil. The potting soil sisters had higher levels of anti-inflammatory proteins that keep the immune system in check.
While we could wait for long term studies on kids who play in natural elements, the truth is that our kids will be adults by then. In the meantime, isn't it still worth encouraging kids to spend time in nature? Soil is actually the most diverse habitat on Earth and the studies seem pretty clear that exposure to diverse bacteria in the environment is one mechanism underlying the wide-ranging health benefits of spending time in nature. Besides, nature play can help a child in so many ways— socially, creatively, gross motor, physically. Not to mention, it’s just plain fun.