What do snowflakes have in common with humans? No snowflake is like another. It’s the same with humans. Over 7.5 billion people live on our planet, yet we are all unique.
In this sense, individual diversity also rules in what is probably the oldest of our organs: the intestine. Its flora is as unique as a fingerprint for every one of us. But what makes this central part of the body so fascinating?
In the beginning, there was the intestine…
Our digestive system is the oldest organ system in the body in terms of developmental history. We humans have developed around our digestion. The main role of digestion is likely played by the small intestine. It is precisely here – after the digestive enzymes have done the necessary preparatory work – that the micro- and macronutrients from our diet, which are so important for us, are transported into the body.
In order to achieve the best possible absorption surface, nature has enlarged the inner surface of the small intestine by several magnitudes. Its mucous membrane lies in millions of wrinkles about one millimetre in size (intestinal villi). The membrane, in turn, bulges continuously into microvilli. This “folding technique” gives the small intestine, which is approx. 4–6 m long, a total surface area of almost a tennis court (approx. 250 m2) – enough space to absorb the vital nutrients and transfer them to the blood and lymphatic system.
The abdominal brain – simply clever!
Before nature decided to form a brain as a control centre for more complex organisms, the first nerve cell structure was the digestive system. This was provided with muscles, mucous membranes, and immune cells. As a further development of this original structure, the abdominal brain now comprises around 100 to 200 million nerve cells, which run through the muscle layers of the intestinal wall. In comparison, a dog – as a very intelligent animal – has only about 160 million nerve cells in its cerebral cortex. As you can see, our abdomen is actually quite clever. For its main task, digestion, it does not need the brain and takes over the helm immediately after food is swallowed.
The talkative intestine–brain axis
Nevertheless, the two clever organs cannot let each other go and are in constant exchange with each other. By the way, our abdomen is much more talkative than our head because 90% of all information goes from bottom to top. No matter whether hunger, satiation, pain, or possible irregularities – our abdominal centre communicates with our thinking centre and vice versa via the “abdominal-brain axis”. We hardly notice what our intestines communicate with our head. Only in certain cases – for example, when unwanted substances enter the gastrointestinal tract and the brain and abdominal brain together trigger physical discomfort – do we consciously and closely experience their communication.
The sensitive abdominal-brain relationship: I’ve got a gut feeling…
Although mental performance and mental work may take place in the brain, we still like to follow our gut feeling when making important decisions: Stress and worries eat away at our stomach, and feelings of infatuation trigger butterflies.
Many researchers now agree that our lives – our emotions and thoughts as well as our decisions and our health – are influenced by the intestine even more intensively than we currently know and suspect. The close relationship between the two control centres is supported by the fact that the two organs (if you look at their development in the womb) are made of the same material. They also speak the same language. Thus, all messenger substances of the brain are also found in the abdominal brain.
The fabulous world of intestinal flora…
The fascination with the intestine does not end with the organic structures of the digestive organ. Instead, it fully blossoms with the intestinal flora (i.e. microbiome). While there are only a few bacteria in the small intestine, the large intestine is covered by a dense bacterial lawn. In fact, it is one of the most densely populated places in the world. Around 100,000 billion germs with at least 500 to 1000 different species form the up to two-kilogram-heavy intestinal flora.
The microscopically small inhabitants that feel so at home in the intestinal mucosa have various tasks: They digest indigestible food components (dietary fibres) and produce substances that supply the top layer of the intestinal mucosa with energy. They form a protective shield against pathogenic germs and prevent their penetration into the body. The intestinal flora also interacts with the intestinal immune system. It trains the immune cells and stimulates the formation of defence substances, which not only benefit the intestines but also other areas such as the nasal mucous membranes. All this makes the intestine an important part of the immunological network. This is also reflected in numbers: The small and large intestine contain 70% of all immune cells and are involved in almost 80% of all defence reactions.
Considering their importance, we might think that the diversity of our intestinal bacteria is in danger. While primitive peoples, such as those in the Amazon region, have many different intestinal bacteria, people in more developed countries have already lost 40% of their intestinal flora species because of lifestyle and diet. This makes it even more important to pay special attention to the intestine and its inhabitants.
If the intestine is good, everything is good!
At the beginning, there is the intestine – not only in terms of developmental history but also when it comes to our well-being and health. An intestine-friendly diet is varied, unprocessed, organic, local, and vegetable-based. But what else can we actually do to make the intestines and their co-inhabitants feel comfortable?
- Intestinal bacteria love fibre: Soluble dietary fibres, which occur primarily in plant foods, are broken down by the bacteria in the large intestine. The ballast serves as food.
- Fill up on bitter compounds: Certain plants rich in bitter substances, such as milk thistle or artichoke, can stimulate the liver and gall bladder and thus support the digestive function of the intestine.
- Maintain the intestinal mucosa: A good supply of vitamins A, B2, B3, and biotin supports the maintenance of normal mucous membranes such as those of the intestine.
- Ready-made products? No thank you! Ready-made products often contain a number of additives that can negatively influence the composition of the intestinal flora.
- Reduce sugar. Sugar fuels the less optimal bacterial and fungal species in our intestines.
- Be careful with medications and alcohol: It is now well known that antibiotics can damage the intestinal flora. It is less well known that other medications and alcohol can also damage the intestinal flora or mucous membrane.
- Keep moving regularly: Those who do endurance sports (e.g. Nordic walking or cycling) three times a week help maintain healthy circulation and intestines. The improved blood circulation also benefits digestion.
- Caution: germ-free! Cleanliness is important. No question! However, excessive hygiene can be detrimental to our microbiome. There’s a reason why children should be allowed to play in the dirt as a precaution.
Franz, M., Gruber, K. 2007. Wunderwelt: Eine Geschichte des menschlichen Körpers [Wonderworld: a history of the human body]. Verlagshaus der Ärzte, 1st edition.
Grillpazer, M. 2006. KörperWissen: Entdecken Sie Ihre innere Welt [BodyKnowledge: discover your inner world]. Gräfe und Unzer Verlag GmbH.
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