Select Page

The last two blogs on this topic were about you and your organs. Today it’s about the gut and all the players that are often considered not to belong to you – your microbiome.

The three-way connection of gut – brain – microbiome

The gut – a long underestimated organ

What comes to mind when you think of the gut? Stool? Food utilisation? Yes, of course these are essential tasks. But the intestine is also responsible for 80% of our immune system. It also produces vitamins and messenger substances and communicates via these with almost all other organs of the body, but above all with the brain. With its incredible length of 6-8m, it offers an even more unbelievable basketball court-sized surface area (approx. 400m2) for the absorption of useful substances and the defence against harmful ones.

Regarding anxiety, we are mainly interested in the tasks of the intestine which have nothing to do with food utilisation and bowel movements.

The defence against harmful substances takes place on three levels. The first is the intestinal flora. Everything that is not destroyed there must be able to pass through the intestinal mucosa. The rest is attacked by the immune cells in the mucosa – macrophages, T-cells, killer cells and antibody-producing plasma cells. Because much of the immune system is localised in the intestine, it is important that these defence cells are connected to all other mucous layers in the body via blood and lymph and can thus share their findings. So the gut is, so to speak, the training centre for the defence system. This analogy is quite fitting, because without training, the body’s defences can be lost or (in children) never develop. Excessive hygiene and disinfection – especially in children – therefore takes away training opportunities from our immune system and makes it susceptible to invaders.

The gut-brain axis

The intestine also has its own huge nervous system – the so-called “enteric nervous system”, also called the ” belly brain”. With more than 100 million nerve cells, it contains more than our spinal cord. And even though the so-called belly brain is usually called the 2nd brain, it is – based on the direction of communication – rather the 1st brain, because about 90% of the information is sent from the intestine to the brain – only 10% from the brain to the intestine.

The belly brain is also evolutionarily older than the brain.  Creatures without a head brain still had and still have a digestive system with integrated nerve cells. And by the way, both brains arise from the same material during embryonic development. And so it is not surprising that they also communicate via the same substances.

In the last article I wrote about the hormonal prerequisites for fears (here:). In that article I also talked about the fact that many of the messenger substances have to be produced in the body as well as in the brain, because they cannot cross the blood-brain barrier. So here is the explanation of how the signals produced by the neurotransmitters get from the gut to the brain. Messenger substances produced in the intestine excite the intestinal nervous system and this transports the corresponding information (e.g. the stomach has a good feeling) via the vagus nerve to the brain.

The microbiome

But the gut is not only the huge mucosal surface and centre of metabolism and immune defence. The gut is also the home of the largest part of our microbiome. An overwhelming number of tiny organisms (microbes) colonise our intestines – as well as our skin and all other organs of our body. Besides bacteria, viruses and fungi also live here. The best researched are the bacteria – of which we carry slightly more than our own body cells in and on us.

Our coexistence with this microscopic world is evolutionarily determined. Over the course of our evolution, we have incorporated 37% bacterial DNA and at least 6% viral DNA into our DNA. By the way, without knowing today in each case what these contribute usefully. (See also my blogs from last year on this topic here:).

This also affects a current discussion. And yes, of course, from mRNA vaccination the corresponding gene strand can also be incorporated into human DNA (source). Emphasis here is on the word “can”. Whether and what, as the case may be, would be the consequence of this incorporation is also not evident from this.

I have also described how important this microflora is for our planet in my blog on viruses and bacteria. I would like to emphasise here once again the ability of bacteria to form groups with social structures. These structures then take over certain tasks that the individual microbe cannot fulfil. Particularly unpleasant for us: the organisation of bacteria in so-called “biofilms”. Biofilms surround the group with a slime that makes it much less vulnerable to environmental influences – such as antibiotics.

How do the gut and microbiome influence the development of anxiety or sad and anxious moods in general?

They produce neurotransmitters and communicate with the brain.

Perhaps you are now also wondering how bacteria (i.e. organisms that are somehow foreign to the body) communicate with our body’s own cells. Researchers have also asked themselves this question and now know at least a little about it, although it has not yet been fully understood. The communication between bacteria and other cells – the so-called “quorum sensing” is controlled by signal molecules. These chemical or electrochemical substances range from highly specialised to very general. So far, no pattern has been identified, which makes it very difficult to find them. And just as they communicate with each other with these substances, this is also possible with our body’s cells.

The microbiome influences, for example, the hypothalamic-pituitary-adrenal axis via this possibility of communication – which in turn is important for the topic of anxiety and also for depression (see the last two blogs about the brain and hormones in relation to anxiety). It also influences the function of the thyroid gland and its hormone production as well as the production of sex hormones. This means that it not only influences our feelings and behaviour, but also our growth and immune defences (source).

The exact way in which the production of hormones and neurotransmitters in the gut is influenced by the different bacteria of the microbiome has not yet been clarified in all its details. However, it is certain that the synthesis of these substances cannot succeed in the absence of the corresponding bacteria, and it is regarded as definite that specific bacteria are themselves capable of producing these messenger substances from the relevant starting materials and thus influencing our mood and behaviour.

They fight off physical diseases that can lead to mental illness.

The bacteria in our gut directly stimulate our immune cells to do certain things. You can read more about this in the interesting article about the work of a team of scientists in Kiel (here:).

Even in the case of Corona, although the virus enters the body through the respiratory tract, the absence of certain bacteria (Faecalibacterium prausnitzii, Eubacterium rectale and bifidobacteria), which strengthen our immune system, has been shown to lead to the severe course of this disease. This disproportion of bacteria favouring our immune system to others obviously also contributes to the symptoms of long covid (source).

The influence of bacteria such as Campylobacter or Escherichia coli can later lead to depression via a severe intestinal infection. Bacteria that cause syphilis and brucellosis are also suspected of having a long-term influence on a rather sad and anxious state of mind. (Source)

Overall, it is now clear that the gut microbiome is linked to diseases such as obesity and diabetes mellitus, to chronic inflammatory processes in the gut and via these also to mental illnesses such as schizophrenia, autism, anxiety disorders and depression. Source)

They are the basic prerequisite for healthy behaviour and life.

Thus, mice born without a microbiome exhibit basically all kinds of strange behaviour. What is particularly sad is that they then often behave in an antisocial and ruthless manner.

You could almost say that our bacteria make us who we are – because for example, experiments with the transfer of certain bacteria turned fearful mice into brave ones, and shy ones into daredevils. It even works across species, because transferring bacteria from depressed people to healthy rats made them depressed.

Studies have shown that people who are well-connected and like to surround themselves with people have a microbiome with a much greater diversity than people who are not so good at social interactions. People who have a wider range of bacterial phyla than others also have significantly fewer feelings of loneliness and more wisdom, are more likely to engage socially and support others more selflessly.

It is interesting to note that the addition of a microbiome to the mice without one only helped to normalise behavioural problems in childhood. In adulthood, it had no effect. This makes it clear once again how important it is to develop a healthy microbiome in childhood. Especially the vaginal microbes of the mother taken in at birth by the child – who is also born without a microbiome – are important for the further healthy life of the baby (this is why in the case of caesarean sections there are already doctors who coat the baby with the germs taken from the mother’s vagina). Children should also be allowed to play in the dirt – the amount of microbes absorbed here is essential for the development of their microbiome.

So, are we helplessly at the mercy of our bacteria?

Not at all, because we can also influence our microbiome backwards. In a study with students who were told to completely change their usual food (i.e. meat-rich, fatty, unhealthy food to fibre-rich, healthy, vegetable-based food and vice versa), the microbiome had already changed within 24 hours (Thomas Bosch, der Mensch als Holobiont, pos. 559). The higher the range of variation of the microbiome, the faster it can adapt.

However, in view of these findings, we should begin to understand that we are not a single organism, but should rather regard ourselves as multi-organismic or even as a holobiont (i.e. a holistic life form). This means that we must understand that within such an organism, communication between different species must take place on an equal level, since suppression of one by the other will almost certainly lead to disaster.

What is science doing with this discovery?

So far, science knows more about the extent to which a dysfunctional microbiome contributes to disease. Exactly which bacteria are needed for improvement or cure is still the subject of research. This is because – as you saw above – the complexity of the system is difficult to assess, and so are the consequences if only one factor is changed. In addition, microbiomes are extremely individual – what works for one can lead to deterioration in another.

Nevertheless, we can safely assume that in the future there will be drugs based on the ability of certain microbes – so-called “psychobiotics”.

There are initial approaches, especially with bifido- and lactobacilli. Even the consumption of a single bacterium – Bifidobacterium longum – over a period of one month not only significantly reduced the feeling of stress in the male test subjects involved; they also actually showed a significantly lower level of the hormone cortisol, even in stressful situations.

And eating yoghurt containing bacteria – from which you surely already know the little lactobacilli – in the morning and in the evening for a month significantly reduced the female test subjects’ anxiety reactions in a study.

Well, what can you do yourself?

Since changing your microbiome can significantly alleviate symptoms of anxiety, it’s definitely worth working on it. It helps even if you have a genetic predisposition to anxiety (source).

1. Only take antibiotics in absolutely exceptional cases.

They should only be used when absolutely necessary. Feel free to ask the prescribing doctor about alternatives. After all, a single dose of penicillin increased the risk of an anxiety disorder 1.3-fold in an extensive study – but in our lives it usually doesn’t stop at a single dose. And studies show that after taking antibiotics, the previously healthy state of the microbiome is restored after 3 years (!) at the earliest (source).

2. Do a gut test.

This is especially useful if you are already suffering from significant stress and/or symptoms of stomach and intestinal problems. The tests will tell you about any inflammation of the mucous membrane of your intestines, as well as any disturbances in the composition of your microbiome that could promote disease. Even though there are self-tests available, in my opinion it always makes more sense to discuss the symptoms with a doctor or non-medical practitioner, because they can determine the individual test parameters based on your symptoms.

3. Influence your microbiome through food.

The way we can consciously influence our microbiome is, of course, primarily through food. Here are the most important tips in brief:


  • Eat as many different vegetables as possible, because you will get different ingredients – antioxidants, vitamins and minerals.
    Look for fibre. You will find a lot of fibre (in that order) in potatoes and Jerusalem artichokes, but also in parsnips, pumpkin, carrots and many types of cabbage.
  • Avoid sugar as much as possible. Sugar increases specific bacteria, which then call for sugar louder and louder, thus increasing their own population, but displacing other – useful – bacteria. In addition, you enable one of the most unpleasant fungi that can grow in our body – candida albicans – to spread.
  • Feed your bacteria with so-called prebiotics. Inulins, beta-glucans and pectins are dietary fibres that stimulate the proliferation of bifido- and lactobacilli in particular. Inulins are mainly found in asparagus, black salsify, chicory, artichokes or Jerusalem artichokes. Pectin and beta-glucans are also nutrients for the “good” bacteria in your gut. Pectin is mainly found under the skin of fruit – a reason to buy it only in organic quality so that you can actually eat the skin. Beta-glucans are complex carbohydrates found mainly in oats – it’s not for nothing that our farming ancestors ate a big bowl of oatmeal in the morning. (By the way, oatmeal is now also available gluten-free – at least in my organic store).
  • Enjoy fermented foods, because lactic acid helps the lactobacilli in particular to multiply. The trend towards self-fermenting is on the rise – a way not only to eat healthier, but also to learn something new again. If you don’t have the courage to try it yet, sauerkraut or kimchi as well as kombucha or water kefir will do. Microbe-enriched yoghurt or kefir – which should, however, be free of other additives – is also a useful way to go. Here, too, I recommend making your own.

Food supplements

  • Include foods with bitter substances in your diet, as they stimulate the work of the liver and gall bladder and thus support digestion. If you’re not a fan of chicory and other bitter leafy vegetables, consider a bitter tea or bitter drops.
  • Make sure you support your intestinal mucosa with A vitamins as well as B2, B3 and B7 and omega-3 fatty acids.
  • Ensure you get enough collagen. This is not only good for your joints, but also protects the functioning of your intestinal membrane and prevents inflammation (source). Good options are collagen powders or bone broths in which collagen is dissolved (after at least 16 hours of cooking).

4. Move moderately.

Moderate exercise gets the gut moving, making it easier for the cells in the gut lining and your microbiome to work. And preferably move in a natural environment, so hiking is probably the best alternative.

5. Reduce your stress levels.

Studies have shown that stress affects the gut flora and that, on the other hand, a stable gut flora helps you cope well with stress. Conversely, this means that prolonged stress destroys your gut flora, making it harder for you to cope – a vicious circle is created.

6. Try probiotics.

It seems safe to say that taking probiotics helps with depression. For anxiety disorders, the results are very different. If you decide to take them, see to what extent the manufacturers ensure that they are actually using living cultures and what justifications they give for using the specific strains in their product.

When I look at the recommendations, I have to grin a bit – basically, this is a return to a way of life that actually corresponds to us biologically and has determined our lives for thousands of years.
And so I hope that this blog has once again made it clear to you how much our way of life – which is far from our actual nature – has an influence on your well-being and mental health.

In this sense I remain as always

Yours, Claudia

GDPR Cookie Consent with Real Cookie Banner