The July/August 2015 issue of More magazine included an article on improving your health that included this item:
“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’s been demonstrated in mice and cancer patients.” (pg 136)
Hmmm, I'm ready to start digging! Tell me more.
If you’ve been sniffing your compost in the hope of feeling these effects, please stop for a minute. Let's consider whether there's real information that could be added to the evidence-based design foundation for Elderyarding® and your aging-in-place garden.
First, let’s look at Mycobacterium vaccae.
This is a bacterium commonly found in soil. It was originally cultured from cow dung in Austria, hence the name “vaccae,” from the Latin word for cow. This bacterium is considered non-pathogenic, or not harmful to humans.
Research has definitely shown that killed cells of Mycobacterium vaccae can become immune-therapeutic agents, based on Ugandan studies in 2000. That is, they can become useful in treating tuberculosis, which is caused by another species of Mycobacterium, called Mycobacterium tuberculosis.
Dr. Mary O’Brien, a researcher in the U.K. working with lung cancer patients was curious about the possibilities in Mycobacterium vaccae and tested it with the patients. The study showed that the patients showed fewer symptoms of the cancer and improved emotional health, vitality and general cognitive function. But the study did not provide a detailed exploration of how the results occurred.
Intrigued by O’Brien’s reported outcomes, researchers in 2007 and again in 2010, studied mice, finding that giving the mice Mycobacterium vaccae stimulated the growth of neurons in their brains, further stimulating the grown of serotonin and norepinephrine. Now, researchers can’t ask mice whether they feel depressed, but they know that the general action of serotonin is to increase positive mood.
OK, here it is, 2015. I found no new studies taking the initial research further.
More recent articles and blog posts simply repeat the original stories by rewriting the information. When you read blogs or other internet media, the articles can only assume that Mycobacterium vaccae will do the same thing in people that it did in mice in the 2007 and 2010 studies.
And, we definitely don’t know whether interacting with the bacterium in the soil by digging in our gardens or stirring compost will have the effect that the researchers in 2010 found when they fed the mice peanut butter containing the Mycobacterium vaccae.
Go out and dig because it’s fun, it’s relaxing, it’s pleasurable to do things with your hands outdoors. But until there’s real evidence, don’t credit that bacterium in the soil for your uplifted mood.
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