Hi everyone!
Today I would like to talk about a seemingly mundane and, let’s face it, slightly disgusting topic. I am talking about the gut.
The gut has a
huge autonomous nervous system that is quite similar to our brain. People knew
for a long time that the gut has a huge impact on our emotions (although
scientists underestimated the gut for quite a while). We have “butterflies in
our stomach” when we are in love, we have to “digest bad news” or “have a gut
feeling” that something is wrong and we “swallow a comment”. But why would we
need a second brain when we already have a very complex brain that works great?
The answer is actually
very simple. Our brain is so important and so sensitive that it is protected
very well. It is surrounded by a thick layer of bones and meninges
and every bit of blood is filtered before it enters the brain. So, the brain is
shielded from the rest of the body but still it needs to react quickly to changes
in the environment. On the other hand, the gut is exposed to almost everything
that is going on: food, hormones, pathogens etc. In fact, the inside of our gut
is really the outside of our body. It also has a huge surface and is our
biggest sensory organ. So, you can think of the gut as a secret spy that is
telling the brain everything that is going on in our bodies. The question is
only how they communicate. There is one very important nerve in our body called
the vagus nerve. It innervates almost every organ and is responsible for
slowing down the heart rate or reducing the blood pressure. Interestingly, 90%
of the nerve fibers between the gut and the brain go from the gut to the brain
and not the other way around!
The importance
of the vagus nerve has been discovered by psychology a while ago. When this
nerve is stimulated in different frequencies, test persons feel either anxious
or calm. In fact, vagus stimulation is a common tool for the treatment of depressions.
Now that we know, that the vagus nerve is important for our emotional wellbeing
and we also know that the gut sends signals to the brain via the vagus nerve,
might it be possible that the gut is able to influence our emotions?
In fact there
is lots of evidence that the gut has an impact on our emotions. As you all
probably know, the gut is covered in a huge variety of different bacteria that
help us to digest food. In one experiment, researchers added some “good”
bacteria (Lactobacillus rhamnosus JB-1) to the food of mice while another group
of mice only got their normal food. Then, the mice were put into a water tank and
it was measured how long they were swimming. The idea behind that is that
depressed mice don’t search for a ground to stand on for a very long time and
give up swimming quickly. Those mice that were fed with good bacteria did swim much
longer searching for a way out than the control mice. Additionally they had
much lower levels of stress hormones in the blood and were better in memory
tests. The effects were reversed when the vagus nerve was cut through. This
experiment indicates that the gut is able to influence our emotions over the vagus
nerve.
Both brain and
gut filter, which influences actually get into the brain and which are not
relevant enough. This way, not every undigested carrot has an effect on our
mood but still we are able to feel cozy and warm after a feast. You can imagine
it like a bouncer who won’t let any emotion in. To study the effects of the gut
on our emotions, experiments have been done with people who have irritable
bowel syndrome. These patients generally have stronger tendency towards
depression and anxiety. In one experiment researchers inflated a balloon in the
colon these patients and compared their reaction to a healthy control group. Those
people with irritable bowel syndrome experienced a feeling of fear and anxiety
after the balloon was inflated while the control group was unaffected. If the
gut is constantly irritated, like it is in irritable gut syndrome, it leads to
increased activities in those brain areas that are usually responsible for
negative emotions. These irritations somehow seem to confuse the bouncer that
decides which information enter the brain.
On the other
hand it was shown that people, who have just consumed lots of fatty acids, show
a weaker emotional reaction to sad pictures than people who have eaten saline
food. So, when we are searching comfort in food, or even binge eat, it is
actually possible to numb our emotions. Don’t get me wrong, I’m not saying that
we should numb our emotions by eating. On the contrary, this can lead to a
vicious cycle. We feel uncomfortable after we have consumed too much fatty food
and will feel unconfident about our bodies on the long term, so we have more
negative emotions. Also, overeating fatty food will irritate the bowel and
lower threshold for negative emotions that are passed on to the brain even
more.
Now we know
that the gut actually has a strong but subtle impact on our emotions. What do
have to do to keep it happy?
The answer to
this question is a little more complicated and requires some background
knowledge. So, I will give the answer to this in a second post that is coming
soon. In the mean time I would like to know, if you ever experienced a connection
between gut and emotions?
All the best!
Stefanie
Post a Comment