Dig down to lift your spirits: soil bacteria act as antidepressants

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Have you ever noticed that people who spend more time outdoors, particularly those who garden regularly, are often cheery? While the exercise, sunshine and general health benefits of being outdoors contributes to a happy disposition, scientists have discovered that some of this cheer comes from a certain bacteria that lives in the soil.

Mycobacterium vaccae, a soil dwelling bacteria, has been found to affect our brains in a similar way to antidepressants. It activates brain cells to produce serotonin, a hormone that helps regulate mood and sleep. Low levels of serotonin are often correlated with moodiness, feeling down and depression.

Soil bacteria are well known, to soil scientists at least, for their contribution to modern medicine and technology. Rapamycin, a bacteria found in the soil on Easter Island is used in anti-fungal medications, and in transplants to stop the body attacking transplanted organs. Ralstonia, a very common microbe, has been persuaded to make isobutanol (a fuel). The difference here, with M.vaccae, is that no alterations need to be made to the bacteria to achieve the desired effects – all you need to do is head outside and play in the dirt.

Researchers from the University of Bristol suggest that M.vaccae works by activating immune cells. Experiments on mice revealed the bacteria simulated the production of cytokines, indicating an increase in immune system activity, as well as an increase of serotonin in the brain.

Experiments at the Sage Colleges in Troy, New York, have also suggested M. vaccae can increase learning abilities, with mice that were fed the bacteria being able to solve maze problems twice as fast as mice who weren’t. These wonderful soil bacteria are a Prozac and IQ booster in one. Best of all they’re free, you just need to head outside and play in the dirt.

It has been argued that we are too clean these days, the antibacterial hand wash, wet wipes and multitude of cleaning chemicals doing more to harm our immune system than help it. The truth is, soil microorganisms play an important role in the development of immunity. We need to be exposed to microorganisms to train our immune systems to defend us.

Those of us who garden or work with soil are exposed to M. vaccae simply by digging in the soil. It can be inhaled, or ingested via water or plants. Home-grown vegetables may contain the bacterium, so growing your own food can help increase exposure.

A key to feeling better, it seems, is to do what health experts have been telling us to do for years. Get outside, get into the garden, and while you’re at it grow some of your own food. You’ll feel better, and you’ll have free food.