Stressed? Spend Time Outdoors to Get Your Mycobacterium vaccae

For the last couple of years, I’ve followed the research of a team out of the University of Colorado, who have been looking into treating stress and anxiety by using microbiotic organisms, and have even been exploring the idea of creating a vaccine to prevent PTSD [post traumatic stress disorder] from occurring.  I wrote about this here almost exactly a year ago.

Dr. Lowry and his team have just published another really fascinating paper.[i]  If you remember, in the post I refer to above from last June, he and his team injected mice with a (heat-killed) bacteria called Mycobacterium vaccae, and in doing so were able to prevent the animals from developing anxiety behaviors when exposed to an aggressive male mouse.  The results of that study were quite dramatic, actually.  Not only were the mice much less likely to develop anxiety but they were also 50% less likely to suffer from stress-induced colitis, and showed way less inflammation in blood measures.

Mycobacterium vaccae is found in soil, and I have noted a number of studies over the last number of years that have shown a wide variety of benefits on stress response and more.  (I’ll come back to this in a moment).  In fact, this article suggests that our lack of exposure to it through our lack of exposure to “dirt,” may provide yet more evidence supporting the “hygiene hypothesis” – although all my regular readers know at this point to call it biome depletion!  We in the industrialized world are simply too far removed from our natural habitat and the native organisms that inhabit it and should inhabit us.

In their past research, Dr. Lowry’s group also found that when they vaccinated rodents once per week for 3 weeks with Mycobacterium vaccae, there were much higher levels of anti-inflammatory cytokines in the part of the brain that regulates stress, anxiety and the fight-or-flight response.

In this present study, they tried to figure out how Mycobacterium vaccae actually works to cause this anti-stress response.  They isolated and purified a triglyceride, a fat (called 10(Z)-hexadeconoic acid, for those who want to know!), from the bacterium and had it interact with big immune cells called macrophages (which both human and mice have).  They found that the fatty acid bound to a particular receptor (PPAR, which is crucial in regulating the inflammatory response) and in doing so, blocked the production of pro-inflammatory pathways.  That is, treating the immune cells with the fatty acid made them highly resistant to inflammation.  Says Dr. Lowry:  “’It seems that once the soil bacterium gets inside the immune cell, it releases the anti-inflammatory fatty acid. This then binds to the PPAR and closes down the ‘inflammatory cascade.’”[ii]

As promised, coming back for a moment to other studies looking at Mycobacterium vaccae:  I did a bit of looking around, and found another really interesting article dating from 2010, describing research presented at a microbiology meeting in San Diego.[iii]  Two tidbits from this really struck me as interesting:

  1. Said one of the presenters of the study:  “Mycobacterium vaccae is a natural soil bacterium which people likely ingest or breath in when they spend time in nature.”  You really do have to wonder if the therapeutic effects of being outside, in nature (which have been proven over and over again), are not just mental but physical, in that people are being exposed to these sorts of organisms.  An interesting thought, right?  I remember when this study came out just last year:  “A new report published today reveals that exposure to greenspace reduces the risk of type II diabetes, cardiovascular disease, premature death, preterm birth, stress, and high blood pressure.”[iv]  If you read to the bottom of this little article on Science Daily, it mentions that, “Much of the research from Japan suggests that phytoncides — organic compounds with antibacterial properties — released by trees could explain the health-boosting properties of forest bathing.”  It’s not just the psychological benefits  of relaxing in natural beauty that lead to physical ones…it’s actual exposure to elements found only in nature that improve our health.
  1. The study presented showed that mice fed Mycobacterium vaccae were not only less anxious under various circumstances, but more than that, were able to navigate a maze twice as fast as untreated mice. The results suggest that the organism also plays a role in learning.  Said one of the researchers involved, “’This research suggests that M. vaccae may play a role in anxiety and learning in mammals…It is interesting to speculate that creating learning environments in schools that include time in the outdoors where M. vaccae is present may decrease anxiety and improve the ability to learn new tasks.’”

As far as I can find, this particular species of bacterium is not available commercially.  However, as suggested above – you can likely get exposed to it just by spending some time in nature.  And that’s a pretty good idea for your mental and physical health anyway!


[i] Smith, DG, et. al.  Identification and characterization of a novel anti-inflammatory lipid isolated from Mycobacterium vaccae, a soil-derived bacterium with immunoregulatory and stress resilience properties.  Psychopharmacology. 2019.





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