New study suggests digging in the dirt could reduce stress, inflammation

A bacteria that’s present in most backyards could help reduce stress says microbiologist Jason Tetro.

Findings into dirt bacteria's healthy properties 'absolutely brilliant,' says microbiologist Jason Tetro

A new study shows getting a little dirty in the garden can have positive effects for gut bacteria and may reduce inflammation and stress, says microbiologist Jason Tetro. (Jesse Johnston/Canadian Press)

New research out of the United States shows a common bacteria present in most backyards could help reduce stress and chronic inflammation, says Toronto microbiologist Jason Tetro. 

A recent study published in the Proceedings of the National Academy of Sciences shows the bacteria mycobacterium vaccae may reduce chronic inflammation, a condition considered a risk factor to stress, said the report's authors.

"These data support a strategy of 'reintroducing' humans to their old friends to promote optimal health and wellness," they said.

Tetro calls the work "absolutely brilliant." 

Researchers looked at how mycobacterium vaccae works inside the body, he said. They grew vaccae, then killed it using heat and injected the dead vaccae into mice, like a vaccine, to see its effects, Tetro said.

"After a while they started looking at how the mice dealt with stress … what was interesting is that the vaccinated mice actually had the ability to cope with stress," said Tetro.

The dead vaccae injection seemed to balance the mice's immune systems.

"The idea is if you are balancing the immune system then you're reducing the possibility of having stress-like symptoms down the road …. anxiety and maybe even post-traumatic stress disorder, could possibly be helped by using this mycobacterium vaccae," said Tetro.

Bacteria known as 'the old friend'

Mycobacterium vaccae is known colloquially as "the old friend," Tetro said.

"Clinical trials over the last 15 years have shown it can help to lower allergic asthma symptoms ... and they've actually even used it to help people fight tuberculosis," he said.

"It seems to be our best friend."

While mycobacterium vaccae is part of the same family as dangerous bacteria like mycobacterium tuberculosis and mycobacterium leprae, which causes leprosy, mycobacterium vaccae is a friendly bug, said the microbiologist.

Scientists are likely years away from developing a clinical trial for a mycobacterium vaccae vaccine but that doesn't mean humans can't benefit from the new research in the mean time.

While gardening can produce a rich array of fresh fruits and vegetables, it also helps improve the diversity of our gut bacteria, said Tetro.

"Getting in the dirt can actually be good for us," he said.

Gardeners do not necessarily have to eat dirt to ingest the healthy bugs, added Tetro. Just getting dirt on your skin and breathing in dirt particles in the air can have positive effects.

"It's really just a matter of becoming exposed to it [dirt] to increase your own human microbial diversity," said Tetro.