A gut feeling. How intestinal system and brain affect each other.

Have you ever damned your gut for causing you trouble at the most inopportune moment? For example, while being on a very important business meeting, a long awaited date, or just at your friend’s house? Scientists found out that there might be a great chance those inconvenient feelings in our abdominal area have something to do with our brain. As long as the intestinal flora is working well, there is no need to spend time on thinking about the digestive system. But the quest for the origin of the problem begins when it is causing its owner mood darkening problems. The question is: Why are we feeling bad when our digestive system is not working well?

As proved in various studies, gut and brain are in a very intimate relationship with each other and therefore they are constantly communicating. Not only the gut sends out signals to the brain, also vice versa, the brain sends signals to the gut when we are feeling stressed or, in a better case, are extremely happy (this is where the butterflies kick in).


There are approximately about 200 million nerve cells that are entrapping our intestinal wall. Via neurotransmitter those cells are involved into influencing not only the digestion but also the brain. Serotonin, for example, which is an endogenous messenger substance, regulates the digestive- and also the immune system. Part of this substance can reach our brain through the bloodstream, where it affects our brains nerve cells. This is the reason why food makes us happy! But, according to new studies, those messenger substances are not the only ones affecting the brain. Scientists found out that intestinal bacteria also influence it. Trillions of bacteria are circulating in our gut and help digesting food– together they build our intestinal flora, which works differently for each person. That is why some people have a “better” digestive system than others.

Just a bad day or maybe bad gut-bacteria?

How did scientists come to those assumptions? Gastroenterologist Stephen Collins from McMaster University in Canada carried out an experiment with mice. He noticed that mice without gut flora behaved unusual: they where adventurous and more willing to put themselves into dangerous situations. But when he colonized bacteria in their intestinal system, they suddenly acted more carefully. It is not fully proved whether these results also apply to the human body, but scientists believe it might be the case. However, this scientific field is yet to be observed more thoroughly. “The exciting results provide stimulus for further investigating a microbial component to the causation of behavioral illnesses”, says Dr. Collins.

In his studies he found out that there is a connection between abnormal bacteria and various psychological diseases such as anxiety, depression or even late onset autism:

“Many people with chronic intestinal conditions also have psychological disturbances and we never understood why. This latest research indicates that while many factors determine behavior, the nature and stability of bacteria in the gut appear to influence behavior and any disruption, from antibiotics or infection, might produce changes in our behavior.”

Before going on your next date, watch out for these following symptoms to prevent any gut disturbances and if you identify with them, an appointment with a doctor would most likely be recommended:

Physical symptoms: Stiff or tense muscles, Headaches, Sleep problems, Shakiness or tremors, Recent loss of interest in sex, Weight loss or gain, Restlessness

Behavioural symptoms: Procrastination, Grinding teeth, Difficulty completing work assignments, Changes in the amount of alcohol or food you consume, Taking up smoking, or smoking more than usual, Increases desire to be with or withdraw from others, Rumination

Emotional symptoms: Crying, Overwhelming sense of tension or pressure, Trouble relaxing, Nervousness, Quick temper, Depression, Poor concentration, Trouble remembering things, Loss of sense of humor, Indecisiveness

Also, take a look at this remarkable TED Talk and learn more about the second brain in your gut!

Header image credits royalty free 

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About Ece Isil Sahin

Ece has fallen for the arts since she was 5 years old. Growing up between backstage areas and theatre cafés, she is now majoring in Theatre-, Film- and Mediastudies at the Universitiy of Vienna.

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