There’s a reason kids love playing in the mud and babies are always putting their dirty hands and feet in their mouthes. They instinctively know that dirt is beneficial. Dirt is full of bacteria that help keep your own good gut bacteria thriving.

Now scientists have found that one of these strains of bacteria living in soil may protect against stress.

In a new study, researchers from the University of Colorado Boulder isolated a fatty acid called 10(Z)-hexadecenoic acid from the soil bacterium Mycobacterium vaccae to see how it interacted with immune cells. They found that the fat blocked pathways that lead to inflammation and cause stress.

“We think there is a special sauce driving the protective effects in this bacterium, and this fat is one of the main ingredients in that special sauce,” says senior author and Integrative Physiology Professor Christopher Lowry in a statement.

The researchers hope to use the bacteria to develop a “stress vaccine” to treat post-traumatic stress disorder (PTSD).

Dirt really can make you happier

In my book “Game Changers,” I talk about the benefits of mycobacterium vaccae on mood. Previous research shows that this specific strain of bacteria has improved the quality of life in cancer patients. In a 2004 study, lung cancer patients at the Royal Marsden Hospital in London were happier, showed more vitality, and had stronger cognitive functioning after being injected with the soil bacteria.[ref url=”https://www.ncbi.nlm.nih.gov/pubmed/15151947″]

In another study, scientists injected mice with the same bacteria, and found that it boosted serotonin levels in a similar way to antidepressants.[ref url=”https://www.ncbi.nlm.nih.gov/pmc/articles/PMC1868963/”]

Related: Can Dirt Double as an Antidepressant? The Mood-Lifting Benefits of Soil Microbes 

“The idea is that as humans have moved away from farms and an agricultural or hunter-gatherer existence into cities, we have lost contact with organisms that served to regulate our immune system and suppress inappropriate inflammation,” says Lowry. “That has put us at higher risk for inflammatory disease and stress-related psychiatric disorders.”

So don’t be afraid to get dirty. Get outside, run around barefoot, or take up gardening. Discover more ways to tap into the natural world for a happier and healthier gut.

Read next: To Live Longer, Here’s Why You Need to Get Dirty