The Dirty Healthy Germ that Gardeners Love: Mycobacterium Vaccae

Bacterium That Gardeners Love: Mycobacterium

Digging for Evidence that Dirt Improves Your Mood

The natural world continually provides amazement, sometimes thanks to technical advances like improved microscopes and other equipment used by scientists every day. ll species. An article in More magazine included a marvelous report on improving your health that included the following information:

“Digging in the dirt may also boost your mood through a surprising mechanism. The common soil bacterium Mycobacterium vaccae causes neurons to produce serotonin, which creates an anti-depressant effect. That has been demonstrated in mice and cancer patients.”

Isn’t this bit of information fascinating? Here’s more…

The Startling Effects of Mycobacterium

If you have been sniffing around your compost pile or putting your nose on the flower bed’s mulch in the hopes of feeling these effects, please stop for a second and consider the evidence. (Evidence-based design is a key concept in Elderyarding®.) So here’s a look at the evidence that research has uncovered.

First, consider Mycobacterium vaccae. M. vaccae is a common bacterium found in soil throughout the world. It was initially cultured from cow dung in Austria, hence the name “vaccae, “ from the Latin word for cow. 

The bacterium is considered non-pathogenic, or not harmful to humans. Starting with studies in Uganda in 2000, research has proven that killed cells of Mycobacterium vaccae can become immune-therapeutic agents. Learn more.

Using Mycobacterium Vaccae to Treat Tuberculosis

One Ugandan study used heat-killed Mycobacterium vaccae in a randomized, placebo-controlled trial of 120 non-HIV infected adults with newly diagnosed pulmonary tuberculosis. Tuberculosis is caused by another species of Mycobacterium, called Mycobacterium tuberculosis. 

The group was randomly split into sub-groups receiving either a single dose of M. vaccae or a placebo one week after beginning treatment and all were followed for a year. The heat-killed Mycobacterium vaccae was proven safe and well-tolerated. And the unpredicted result was that 35% of the people in the M. vaccae group showed a successful change in their disease compared to only 14% in the placebo group.

Another research team led by Dr. Mary O'Brien, a researcher in the U.K. working with lung cancer patients, was curious about the possibilities of using M vaccae for lung cancer patients. She tested it with patients and found that patients showed fewer symptoms of cancer and improved emotional health, vitality and general cognitive function. However, the study did not provide a detailed exploration of how the results occurred.

Intrigued by the results of Dr. O'Brien's study, researchers in 2007 and again in 2010 studied the effects of M. vaccae in the brains of mice to further develop her initial findings. What they found was fascinating. Mycobacterium vaccae stimulated the growth of neurons in the mice brains, also boosting the growth of serotonin and norepinephrine. Of course, researchers cannot ask mice whether they feel depressed, but they know that the general effect of serotonin is to increase positive mood.  Learn more.

The Latest Findings

Building on this previous work, the most recent studies have looked at the relationship between bacterium, inflammation, and mood over the past few years. Researchers have hypothesized that conditions like depression might be caused by brain inflammation, and it is possible that this inflammation could be modulated by bacteria like M. vaccae in our microbiome. 

Research conducted at the University of Colorado Boulder in 2016 suggests that Mycobacterium vaccae can have beneficial anti-inflammatory effects on the brain. The recent study, again using mice, found that through injections of the bacteria, the animals can be virtually “immunized” and show no anxious responses to a stressful situation. 

The initial research at CU Boulder was focused on the immune-modulating properties discovered by Dr. O'Brien. After injecting the mice with heat-killed M vaccae, the researchers found that treated mice showed less anxiety and fear-based behavior when placed in an enclosure with a larger, aggressive mouse.

Further study found that rats injected with a series of three doses of heat-killed bacterium had increased levels of interleukin-4 in the hippocampus. I-4 is an anti-inflammatory protein, and it is thought to help modulate moods like anxiety and fear. The results could lead to a probiotic, M. vaccae based drug that can address illnesses from depression and anxiety to PTSD and Alzheimers.

Of course, the results are preliminary and ongoing research is needed to develop the possibilities for this fascinating bacterium further.

The Takeaway...

Further research is needed, but the results look promising. When reading about these studies in blogs or online, it is important to understand that the results are preliminary and we are still not sure if Mycobacterium vaccae will do the same things in humans as it appears to do in mice, but researchers are getting closer to an answer.

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We don't know whether interacting with the bacterium in the soil by digging in our gardens or stirring compost will have the effects that researchers found in 2010 when they fed mice peanut butter containing M. vaccae, and in 2016 when they injected mice and rats with heat-killed M. vaccae. 

For now, continue to go out and dig in your garden because it's fun, it's relaxing, and it's pleasurable to do things with your hands outdoors. However, until all the results are in, don't credit that bacterium in the soil for your uplifted mood. It may just be the sunshine, sense of accomplishment, or maybe just because it's fun! 

Ann Yakimovicz