Scientists Are Following Their Gut
Whenever I’m nervous, frightened or upset, my stomach is the first place to feel it. My appetite disappears and I find that I’m subconsciously clutching my abdomen. It’s a pretty common reaction.
And how often have you felt a “Gut reaction” that something was good or bad, or been told to “Follow your gut”?
It seems we’ve always recognized intuitively that there is a connection between our stomach and our brain. And now, scientists have begun to find physical evidence to back our intuition.
We’ve known for a long time that we have bacteria in our stomach that helps us to digest our food. But this microbiome, as they are collectively known, also appears to have a connection with our mental health and personality.
And the effect is not just one way:
Scientists found that the brain has a direct effect on the microbiome, creating and changing not only our gastrointestinal functions, but our immune reactions as well.
At the same time, those microbes in the stomach create substances, such as the neurotransmitter serotonin, that have a direct effect on the brain functions.  Up until recently, it was thought that only the brain could produce neurotransmitters.
Now so far, these experiments have all been carried out on mice. But they’ve also used microbes from humans, and I’ll have more on that in a moment.
First, let me tell fill you in on some of the background experiments:
Because the microbiome in our gut is produced from exposure to lots of microbes in the environment, scientists raised mice in completely sterile conditions. They then took some of the microbes from a shy and anxious mouse, and introduced them into the gut of the sterile-raised mice. The sterile-raised mouse became shy and anxious.
They tried several variations of the same experiment, and each time, the mouse receiving the microbes took on the behavioral characteristics of the donor mouse.
Then it got even more interesting:
The scientists took some microbes from a human who suffered from anxiety and depression, and exposed them to the sterile-raised mice. The result was the same — the mice quickly began to show symptoms of depression and anxiety.
One implication of this is that we could change the nature of the microbiome in order to change the behaviour of our brain.
Scientists began to explore this idea with mice that were suffering from intestinal leaks, showing repetitive behaviour and were shy and uncommunicative with their fellow mice.
They treated these mice with anti-inflammatory bacteria (Bacteroides fragilis) and the results were amazing. Not only did the leaky gut problem resolve, but there was also a marked reduction in the repetitive behaviour and the mice began to spontaneously interact more with the other mice. 
So, although research is at an early stage, scientists seem to be making speedy progress. This is good news for anyone suffering from gastrointestinal disorders and/or behavioural or mental health issues.
And it also verifies our own human intuition. Clutching my abdomen whenever I’m upset, albeit subconsciously, has a sound scientific basis.
 Yano et al., 2015, Indigenous Bacteria from the Gut Microbiota Regulate Host Serotonin Biosynthesis ,Cell 161, 264–276 April 9, 2015 Elsevier Inc. http://dx.doi.org/10.1016/j.cell.2015.02.047
 (Hsiao et al., Microbiota Modulate Behavioral and Physiological Abnormalities Associated with Neurodevelopmental Disorders, Cell (2013), http://dx.doi.org/10.1016/j.cell.2013.11.024) http://poo.caltech.edu/static/pdf/EYHCell.pdf