We all know what it's like to be sad about things (have you looked at the steem chart on poloniex recently?... jeez), and many of us know what it's like to truly experience depression. It's one of the most common of all mental illnesses and effects up to 7% of the worlds population. [2] That's a lot of people...just over 520 million (more people than live in the US and Canada and Mexico... COMBINED). There are a lot of ways to treat it, and recent research describes some results that may surprise you. The symptoms of depression may have at least some relationship with our microbiome.

One bacteria in particular called Lactobacillus was observed to be particularly important, and what in our diet is a major source of this Lactobacillus?

This post describes some work published in the journal Nature: Scientific Reports on March 7, 2017 titled "Microbiota alteration is associated with the development of stress-induced despair behavior." and in this article authors were looking at the effects that the microbiome had on the symptoms of depression.

How Were They Studying This?

Well as usual, the studies reported here were done in mice. Which is a common model used for exploring these sorts of things, however we must be cognizant that the biochemistry of mice is not exactly the same as in a human so sometimes what we observe in mice doesn't end up translating to a human. However, as far as initial research like this is concerned, testing in mice is great for allowing us to gain greater insights where we may want to potentially take human studies. After-all, we don't want to be messing around with the microbiome of our fellow humans and do something potentially disastrous, better to let the disaster fall on the mice (as sad as that is too!)

Sorry little guy, this was a shitty way for you to find this out!

Uhhh... @justtryme90... What is a Microbiome Again?

The microbiome refers to the collection of all of the bacteria that live in the digestive tract in each our bodies (or the bodies of a mouse). Studying these bacteria and the effects that they have on various processes in our body (and there are some fascinating findings being published recently) is a hot topic in research right now.[3], [4] For the longest time scientists were under the impression that they didn't really play a role in our health, however we are finding that not to be the case at all!

So What Were They Doing Here?

Well they were looking at what stress does to the microbiome composition in the mice. What they found was that chronic stress conditions resulted in a reduced amount of the Lactobacillus bacteria in the mice (they did this by quantifying the amount of the bacteria in the mice poops... not a job I would want to have!):

Image reproduced from a figure in [1]

They also found that the stressed mice were less likely to try to try to escape an uncomfortable situation (aka here they forced the mice to swim.. poor little things):

Image reproduced from a figure in [1]

And as you can see in the plot above the display of escape behavior was correlated to the amount of lactobacillus in the mouse microbiomes. Reduced escape behavior is a symptom of depression in the mice.

So what about if the stressed mice were are supplemented with Lactobacillus... will they try to escape more?

Yep, though the data isn't as obvious as one would like, its still there.

Image reproduced from a figure in [1]

So the first bar graph shows that when they supplement the mice with lactobacillus (orange bar) that there is a lot more in their poop. The second set of graphs on the right shows the difference in escape behavor between unsupplemented unstressed and stressed mice (the blue and red...see the red stressed bar is low in escape behavor) versus the supplemented (light blue and orange bars) the orange bar does not decrease as much as the red bar does, showing that supplementation of the Lactobacillus helped (at least some!) with the mice dealing with the stress. AKA they were less depressed, and wanted to stop swimming a helluva lot more!

Why Do Lactobacillus Have Anything To Do With This?

The answer lies in the kynurenine synthesis pathway. Kynurenine is known to be involved in depression, and that inhibiting this synthesis pathway can lead to an alleviation of depression symptoms. [5]

Image reproduced from a figure in [1]

The authors discus how hydrogen peroxide can inhibit this pathway, and showed that Lactobacillus can produce hydrogen peroxide.

Image reproduced from a figure in [1]

Thus they hypothesize that the reduction in the synthesis of kynurenine by the production of hydrogen peroxide is what results in the reduction in depression symptoms in the mice.

Take Away

Well don't go assuming that this is a clear indication that your depression can be cured by eating more yogurt. You can see here that the results aren't some miraculous recovery for these mice. However there is a pronounced effect. This result may not carry over into humans, either. However, it does seem to indicate that having more Lactobacillus in our microbiomes MAY help us deal with stress some, and may also help us feel a bit happier. Yogurt is a fairly healthy dairy option, so if you enjoy it, eat it with pride. You may be doing your mental health a little bit of a favor!

Sources

All Non Cited Images Are From Pixabay.com And Are Available Under Creative Commons Licenses

Any Gifs Are From Giphy.com and Are Also Available for Use Under Creative Commons Licences

Images from figures in Nature: Scientific Reports articles are available for reuse under a Creative Commons license.

If you like this work, please consider giving me a follow: @justtryme90. I am here to help spread scientific knowledge and break down primary publications in such a way so as to cut through the jargon and provide you the main conclusions in short and easy to read posts.

Thank you for your continued support of my work! I appreciate all those who follow me (and those who don't too, but I appreciate you much much less ;) ).