The Mind-Gut Connection is something that people have intuitively known for a long time
but science has only I would say in the last few years gotten a grasp and acceptance of
this concept.
It essentially means that your brain has intimate connections with the gut and another entity
in our gut, the second brain, which is about 100 million nerve cells that are sandwiched
in between the layers of the gut.
And they can do a lot of things on their own in terms of regulating our digestive processes.
But there’s a very intimate conversation between that little brain, the second brain
in the gut and our main brain.
They use the same neurotransmitters.
They’re connected by nerve pathways.
And so we have really an integrated system from our brain to the little brain in the
gut and it goes in both directions.
The little brain, or the second brain, in the gut you’re not able to see it because
as I said it’s spread out through the entire length of the gut from your esophagus to the
end of your large intestine, several layers of nerve cells interconnected.
And what they do is even if you – and you can do this in animal experiments if you completely
disconnect this little brain in the gut from your main brain this little brain can completely
take care of all the digestive processes, the contractions, peristaltic reflex, regulation
of blood flow in the intestine.
And it has many sensors so it knows exactly what’s going on inside the gut, what goes
on in the wall of the gut, any distention, any chemicals.
All of this is being picked up by these sensory nerves, fed into the interior nervous system,
the second brain.
And then the second brain generates these stereotypic responses.
So when you vomit, when you have diarrhea, when you have normal digestion, all of this
is encoded in programs in your second brain.
What the second brain can’t do it cannot generate any conscious perceptions or gut
feelings.
That really is the only ability that allows us to do this and perceive all the stuff that
goes on inside of us is really the big brain and the specific areas and circuits within
the brain that process information that comes up from the gut.
Still most of that information is not really consciously perceived.
So 95 percent of all this massive amount of information coming from the gut is processed,
integrated with other inputs that the brain gets from the outside, from smell, visual
stimuli.
And only a very small portion is then actually made conscious.
So when you feel good after a meal or when you ate the wrong thing and you’re nauseated
those are the few occasions where actually we realize and become aware of our gut feelings.
Even though a lot of other stuff is going on in this brain-gut access all the time.
When we talk about the connection between depression and the gut there’s some very
intriguing observations both clinically but also now more recently scientifically that
make it highly plausible that there is an integrate connection between serotonin in
the gut, serotonin in our food, depression and gut function.
On a clinical level there’s a connection because many patients with depression also
complain of constipation.
So a distinct dysfunction of the gut.
And often the medications that people with depression take, particularly the serotonin
reuptake inhibitors such as Prozac and all the other drugs in this category, they often
cause transient gastrointestinal dysfunction.
So that’s on the clinical level.
However, what makes it particularly interesting and still an open question really more than
95 percent of all our serotonin we have in our organism is really produced and stored
in the gut in specialized cells, so-called enterochromaffin cells.
So our major by far the largest store of that molecule that plays such a big role in modulating
our mood and our wellbeing, also appetite, pain, sensitivity is stored in the gut.
And a lot of very interesting discoveries have been made more recently that makes this
even more intriguing.
So this serotonin is synthesized in the gut from precursors that come from our food that
we ingest and the microbes that live in the gut are actually able through chemicals that
they produce to stimulate the production of serotonin.
It’s been estimated based on studies in animals that 60 percent of the production
is due to these signals that come from the microbes that live in our gut.
So in addition another intriguing finding is that these serotonin cells, so they’re
sandwiched in between the cells that make the lining of the gut.
One end sticks into the inside samples, everything that goes on inside the gut.
The other side very interestingly has an outgrowth which connected through a synapse with sensory
nerve endings.
So many vagal nerve endings.
So this is a cell that sticks into the gut, samples a lot of things that go on in our
digestive tract.
Then it produces serotonin largely through the influence of microbes that live in our
gut and then the signal when this cell is activated there’s many things chemical or
mechanical stimuli associated with digestion.
It signals through this synapse directly into our brain through the vagus nerve into centers
that have to do with – I mean ultimately with emotional regulation and emotion generation.
So even though we don’t have the proof for that it would be very difficult to mention
that there’s not a significant influence on our mood and that this system if it’s
out of balance does not play a significant role in the pathophysiology of depression.
There’s many food items that contain neuroreactive molecules signaling substances including oysters,
chocolate and many other foods that to varying degrees contain either the precursors of serotonin
or actually serotonin molecules.
It’s possible that these contents of this molecule are the basis for some of these claimed
effects of food items like oysters as an aphrodisiac or mood enhancer like with chocolate.
People say they feel a lot better after they eat their daily piece of chocolate in the
evening which is pretty true.
Not just from the taste but from this chemical connection.