Gut-Brain Axis: How the gut influences our personality

The intestine is not only involved in digestion. Fascinating research results show that it also influences many other complaints, far from digestion. But how much does our gut, along with its community of bacteria, have to do with obesity, diabetes, or our mood? And how does it manage to do that at all? What we learn changes our view on the development of many ailments.

The gut-brain axis: How the gut communicates with our body

The gut seems to be for our health what Frankfurt Airport is for air traffic: an important hub where information comes in, but also gets sent throughout the whole body. In order to understand the connections, researchers are trying to find out how this communication works.

That our mood affects our stomach and intestines or that we need to digest bad news first, everyone has felt at some point. But communication goes both ways. And the flow of information from the head down towards the gut is only a fraction of what happens in the opposite direction: The brain in the head and the gut are connected via a veritable data highway, the gut-brain axis. And who is in charge here is already evident by the fact that about 90 percent of the information in this nerve strand is sent from bottom to top, that is, from the gut towards the head. Only about the remaining 10 percent can our head exert its influence. This creates a completely new picture of health and disease, in which the gut plays a much more significant role than just a digestive organ.

The communication between the enteric and the central nervous system takes place via messenger substances, so-called neurotransmitters. These include serotonin, dopamine, and gamma-aminobutyric acid (GABA). These are produced in both the CNS and the ENS, allowing the gut and the brain to communicate and influence each other reciprocally.

How the gut influences our personality

Research in this field is still in its early stages. However, more and more connections between the intestinal microbiome and our brain are being discovered. The trillions of bacteria in our gut can even influence our mood and personality. We have summarized the initial research findings for you:

High spirits and motivation

Serotonin, also known as the happiness hormone, is produced in the gut from the amino acid tryptophan by 90 percent and is crucial for good mood, motivation, and balanced emotions. Tryptophan is produced, among others, by the "good" bacteria Bifidobacterium infantis. The more of these bacteria are present in the gut, the more serotonin is produced. For example, stress or an unhealthy diet can damage the microbiome, resulting in less serotonin being produced.

Depression

Researchers at the University of Leuven in Belgium have analyzed the relationship between the microbiome and our behavior in studies. For this purpose, stool samples from more than 2000 healthy and depressed individuals were examined. The result: Depressed individuals had a lack of various bacterial genera in their gut. Whether this lack has caused the depression or is a consequence of the depression itself, further studies will need to show.

Anxiety

Scientists from McMaster University in Ontario studied the behavior of mice after receiving antibiotics. The result: rodents that received antibiotics and subsequently developed an imbalance in the gut flora became more anxious than before. Additionally, the levels of BDNF in the mice's brains changed. BDNF is a protein that is correlated with depression and anxiety. When the antibiotic was discontinued, not only did the gut flora normalize, but so did their behavior.

Stress

Studies from the University of Oxford show that even our stress levels are influenced by gut bacteria. Over three months, participants consumed an extra portion of fiber. These fibers are a popular food for "good" gut bacteria, promoting their growth. And indeed: the amount of the stress hormone cortisol decreased significantly, evidence that the stress level has decreased.

Saturation and feeling of hunger

The enteric nervous system in the gut also influences our hunger - and thus, in another way, our weight. The nervous system in the gut evaluates the nutrient content of our food. If it is found to be lacking during this evaluation, a signal is sent upwards. The brain signals hunger, or in some cases even cravings, if we have not eaten as our body requires during the day.

Furthermore, gut inhabitants also influence what we want to eat. They produce molecules that interfere with appetite-regulating peptides and hormones. Also, through their release of neurotransmitters such as serotonin, acetylcholine, and norepinephrine, gut bacteria can influence our mood and thus indirectly our eating behavior.

As you can see, the microbiome in the gut determines much more than the strength of our immune system. Researchers now agree that dysfunction of the gut-brain axis can also lead to the development of neurodegenerative and mental illnesses.