When Gen Xers and Millennials were kids, playing outside wasn’t much of an option. That’s just what you did.

Well, it turns out that moms forcing them out into the sunshine might have led to some serious benefits to our immune systems.

According to recent findings reported in Science Advances, letting your kids play outside in natural environments for just one month can lead to a more effective immune system.

The researchers involved studied 75 children between the ages of 3 and 5, watching to see how environmental changes altered their skin and gut microbiota. They also tracked immune markers in their blood.

A natural environment includes no gravel, concrete, or plastic playthings but does require open spaces, trees, earth, and grasses.

The microbiota of the kids with the new, natural outdoor spaces had shifted completely, and featured a higher ratio of the anti-inflammatory proteins to pro-inflammatory proteins in their blood, indicating their immune system was improving.

Dr. Aki Sinkkonen, one of the study authors, elaborated in a statement.

“We were surprised that the findings were so clear even though we did not get as many participants as we had hoped.”

If you’re wondering why the microbiota of these kids was so important, and so telling, it’s because they have a huge impact on our wider health.

The trillion of microorganisms that live on and inside us can influence our risks of certain diseases, food cravings, mental health, and sometimes even our personalities.

What this study seems to prove is that our surroundings and lifestyles can play a huge role in the richness and diversity of bacteria in our bodies, and that’s not typically a bad thing.

So,  go camping, take hikes, go skiing or swim in a lake – the more natural environments you can expose your littles (and yourself!) to, the better off everyone will be in the long run!