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How does the intestinal flora affect the brain?

When it comes to general health or specifically intestinal health and digestion, the term intestinal flora almost always appears at some point. The terms “intestinal flora” and “intestinal microbiome” are poorly understood.

The term intestinal flora refers to the microorganisms that colonize the intestines of humans and animals. More than 1000 different types of bacteria with a total of about 100 billion cells form the microbiome, which weighs between 1.5 and 2 kg in an adult.

In addition, they fulfill important tasks in digestion and metabolismThe microbiome keeps toxic contaminants and other harmful contaminants away from your body.

These important and hard-working microorganisms in the intestine affect your body and your health. They not only affect the intestine and digestive functions. The intestinal flora can even affect your brain among other things.

How does the intestinal flora affect the brain?

You can buy probiotic dairy products to help the digestive and immune system, but bacteria and microorganisms in your gut do much more. So that you can give the maximum, it is very important that your intestinal flora is intact. Only then will it have a positive effect on your body and protect your health.

But how can the microbiome in your gut affect your brain?

First, you should know that the brain is controlled by various chemicals. They are also found in the stomach through food and from there they reach the intestine.

The way these chemicals are taken from food and processed in your digestive tract is a multi-layered complex that includes amino acids, among other things. However, intestinal bacteria are also significantly involved in the production of neurotransmitters such as dopamine, serotonin, and GABA, which are important for brain metabolism.

The three neurotransmitters are particularly responsible for this:

  • Serotonin: Serotonin is known as one of the happiness hormones. It improves mood and has an antidepressant effect. The intestinal bacteria Bifidobacterium infantis plays a role in its formation by producing tryptophan, a basic component of the hormone serotonin.
  • Dopamine: Dopamine is also reputed to be a happiness hormone, and apparently has a positive effect on motivation.
  • GABA: GABA (gamma-aminobutyric acid) can only be developed by intestinal bacteria. Reducing the transmission of nerve impulses, ensures a good night’s sleep and counteracts the symptoms of stress.

The microbiome has positive effects on brain functions

Little is known that effective neurotransmitters in the brain do not originate in the brain itself. In some cases, they are almost 100% in the intestine.

With the right knowledge about bacteria in the intestine and the effects of neurotransmitters, everyone can improve how they feel psychologically. For example, with probiotic dairy products such as yogurt.

A study at the “University of California” in Los Angeles provided evidence. 25 healthy women participated. Half of them ate two cups of yogurt with live strains of bacteria, such as bifidobacteria, twice a day for four weeks. The other half did not.

Both before and after the study, the 24 participants underwent brain scans to record their feelings of happiness, pain, and anger. In both groups, there were significant differences in favor of yogurt consumers.


Probiotic yogurts had improved the quality of the microbiome in the intestine, which in turn led to the formation of improved neurotransmitters, which in turn improved mood.

The other group had to do without these effects. Their happiness did not increase, and negative feelings such as pain and anger were not relieved.

An unfavorable diet and also an excessive amount of stress have a negative effect on intestinal bacteria and, consequently, also on the production of neurotransmitters.

The descriptive term intestine-brain axis exists for the causal connection between the intestine and the brain.

intestinal flora

Healthy intestinal bacteria

It is extremely exciting to see how bacteria in your gut not only play a role in digestion, but also control your brain.

A team of neuropathologist scientists at the University Hospital of Freiburg has shown that these bacteria in the intestine influence the immune system of the brain.

Researchers believe that the course of neurological conditions such as multiple sclerosisParkinson’s disease, and Alzheimer’s disease depends, among other things, on what bacteria have colonized the intestine.

It is also worth mentioning the Microglia, a kind of macrophage. Macrophages are also known as phagocytes. Cerebral microglia eliminates dead brain nerve cells and germs that have entered the brain.

Microglia dysfunction may be involved in several brain disorders, among other factors. At least in animal experiments, there was a clear correlation between intact bacterial colonization and high-performance microglia.

On the contrary, immature, atrophied and, consequently, insufficiently functional microglia formed when the bacteria in the colon were destroyed or damaged. “ 

Even if animal experiments cannot always be transferred to humans. Given the relationships described here between a healthy gut microbiome and its effects on the brain, a comparable result can be expected in humans. ”

Dr. Marco Prinz

Behavioral control through the intestinal flora?

It is possible that not only the mood is controlled, but also the behavior of the intestinal flora.

An experiment in which shy mouses received the microbiome of entrepreneurial mouses gives rise to this assumption. The shy mouses changed their behavior making them more daring.

It is also spectacular to discover that the bacteria in the intestine act at the level of the neurotransmitter and, therefore, communicate with the neurons.

Certain metabolic products stimulate the production of serotonin in the cells of the colon wall.

In humans, more than 90% of serotonin is formed in this way. There is much to suggest that the intestinal microbiome also has a significant impact on the production of serotonin. As a result, the microbiome acts on the brain.

You can positively influence your intestinal environment

The probiotic bacterial strains mentioned above are not only found in dairy products such as yogurt and kefir. That would be tragic because not everyone likes or wants dairy products.

You will also find the valuable bacteria and yeast of lactic acid, in relevant quantities, in various vegetables such as onions, leeks, cabbage, broccoli, artichokes, asparagus, chicory, as well as in pickled vegetables such as sauerkraut and pickles.

Kimchi also has a positive effect on the intestinal environment.

What damages your intestinal environment?

It is not only important to know what has a positive effect on the intestinal environment, but also what is damaging it.

You probably know or even feel that antibiotics can destroy intestinal flora.

The more you support it, with a healthy diet and, best of all, additional probiotics, the faster your intestinal environment will be fine. On the contrary, unfavorable eating habits do not lead to a healthy intestinal environment, as you can imagine.

Unfavorable eating habits not only harm healthy intestinal bacteria but also counteract the effects of healthy foods that have been enjoyed in the meantime.

It is worth mentioning here the sugar and sweets made with it or the meat of conventional livestock farms that often contains antibiotics.

Unless you’re vegetarian or vegan, you should buy organic meat. In general, you should prefer organic quality in your diet, including dairy, vegetables, and fruits.

Regardless of diet, higher levels of stress can negatively affect your gut microbiome.

Do probiotic supplements make sense?

Not only does it make sense, but it is recommended to take probiotic supplements to support the beneficial effects between the intestine and the brain.

Probiotics are naturally contained in different proportions in vegetables or yogurt. Probiotic supplements will ensure that you get enough of these important substances.

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