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The Human Intestine as Part of the Digestive Tract

The human intestine is a part of the digestive tract, which contributes to the digestion of food and the passage of nutrients to the blood and the rest of the body in the bilaterians. This part of the digestive tract extends from the exit of the stomach to the anus. In humans and most mammals, it is divided into two parts called the small human intestine and the large human intestine. In animals with the circulatory system, it is the part of the body that ensures the assimilation in the blood of nutrients from food. The healthy gut is a barrier against some microbes, but permeable to nutrients. It is the site of an intense microbial life (intestinal microbiota, human intestinal microbiota). Any abnormal alteration of its permeability can affect the whole organism.

A new discipline has emerged, neuro-gastroenterology linking neuroscience and gastroenterology. Neurogastroenterology is the study of nerve control of the motor and secretory activities of the digestive system by the peripheral (paravertebral and enteric nervous system) and central (brain and spinal cord) nervous systems.The Human Intestine


Neurogastroenterology is a discipline that goes back to the work of the French physician Jean-François Fernel, discoverer of peristalsis, in 1542. This mechanism was then studied by William Bayliss and Ernest Starling in the nineteenth century in England. However, it was not until the end of the nineteenth century that the German Paul Trendelenburg observed that a segment of the intestine placed in a jar continued its intrinsic motor activity.

Neuro-gastroenterology studies the role of neuronal or non-neuronal intestinal cells (glial, interstitial Cajal), interactions between different nervous systems (enteric, autonomic, central) forming the brain-intestine axis, chemical mediators. It confirms the importance of regulating the complex functions of nutrient uptake and protection against toxic environmental factors.

The Existence of a Second Brain

A few years ago, scientists discovered in us the existence of a second brain: the 200 million neurons of our belly. New studies highlight and clarify the links between intestinal bacteria and the mind. In 1999, a neuro-gastroenterologist from Columbia University in New York, Michael Gershon, called it the amazing term, the “second brain.”

Communication between the central and enteric nervous systems is like a two-way highway, but with ten times more traffic up than down.

These two brains present an essential common point: the presence of a nervous center. The first brain is the central nervous system. The second is the enteric nervous system.

This enteric nervous system is likely to be studied more closely by neurobiologists, who see it as an organ capable of expressing very early serious pathologies of the brain.

The intestinal neurons are derived from the same embryonic neural plate as the cerebral neurons that form the neural tube and the head. But they colonize the digestive tract from top to bottom, up to seven weeks of pregnancy. They then connect to form the networks, without any other structure, just like the encephalon.

The Fetus Being in a Sterile EnvironmentImportance of Environment

The fetus being in a sterile environment, its digestive tract is also free of any bacteria. At birth, during natural birth, rupture of the protective membranes causes the baby to come into contact with the vaginal and intestinal bacteria of his mother. The latter then conquer this new environment, during the first two years of life.

Then there are the bacteria that are not always “good” in the environment, especially during a cesarean or following antibiotic treatment, depending on the diet (breastfeeding or bottle) or if the child is premature.

The vagus nerve allows the human intestine and the brain to communicate constantly, sending information through the neurotransmitters. On 10 communications between the brain and the intestine, 9 are emitted by the digestive tract. This communication helps to protect the body against certain dangers: for example, in the presence of infected food, the human intestine will alert the brain via the vagus nerve; the brain will then signal to the human intestine to stop the process of digestion.

Enteric Nervous System

The human intestine is a complex organ: connected to the brain by the vagus nerve, it has 200 million neurons, secrete about twenty neurotransmitters, the same as the brain and produces up to 70% of the body’s immune cells, as well as that many bacteria. This nervous system is very autonomous.

He is responsible for functions that are not subject to voluntary control: peristalsis (muscle contractions that allow the growth of the food bolus), gastric secretions, vomiting.

With a length of about 8m in the adult man, representing a surface of 200 m2, the equivalent of a tennis court, the human intestine is the part of the digestive system that includes the small intestine (duodenum, jejunum, ileum) and the large intestine (colon). Very innervated, it contains 200 million neurons that are supported by 2 billion glial cells (support cells).

In the folds of the human intestine are lodged 100,000 billion bacteria  – Ten times more than the number of cells constituting the body. They form the intestinal microbiota (intestinal flora), rich in 800 to 1000 different species.

The term microbiota refers to all bacteria in the body, and the microbiome refers to the living environment of these bacteria colonies.

Without the microbiota, we would be unable to assimilate certain foods that only bacteria know how to degrade.

The Two Essential Functions of the Human Intestine (The Second Brain)

This second brain performs two essential functions:

* The regulation of digestion (emptying the stomach, moving food in the small intestine to the colon).

* Management of nutrient uptake by cells of the intestinal wall. This wall also acts as a barrier against external pathogens. It collaborates with the immune system in defending the body against hostile substances and microorganisms.

Essential organ for survival, the digestive tract allows the digestion and absorption of food while protecting the environment (bacteria, viruses, toxic).

Gut microbiota bacteria affect the health and efficiency of the immune system and can even alter our genetic structure. They constantly interact with our nervous system and play an important role in our brain function, mood and behavior. An imbalance of the intestinal flora (represented by the absence of some of them) would be at the origin of many diseases.

The Link Between Brain and the Human Intestine: The Symptoms Merge

The enteric system contains more than 200 million neurons and many neurotransmitters.

Serotonin, for example, is a neurotransmitter that regulates mood; it is produced in the brain and absorbed by the hypothalamus, which is responsible for well-being.

The intestines also produce serotonin. For a long time, it was thought that this serotonin simply served to regulate the transit and regulate the immune system. Only recently researchers have discovered that serotonin produced by the intestines travels through the blood to the brain. And the intestines are responsible for 95% of serotonin production in the body, directly involved in psychological imbalances causing stress, anxiety, and phobias. Stress causes the digestive system to produce a hormone called ghrelin, a hormone that modulates anxiety and depression.

Candidiasis Would Block the Synthesis of Serotonin

Candidiasis would block the synthesis of serotonin in the human intestine reducing the level of this neurotransmitter in the brain. A possible link between depression and candidiasis has been noted. Ironically, the drug Prozac used for depression has an antifungal effect.

The neurons of the enteric nervous system produce as much dopamine, this happiness hormone, as the brain.

Since neurotransmitters in the brain are also present in the gut, certain drugs intended to act on the brain also have effects on the intestine.

This is, for example, the case of antidepressants, benzodiazepines, but also beta-blockers: when we start a treatment, as the intestine contains many receptors for these molecules, there is blockage of contractions and peristalsis, it happens have nausea or diarrhea but they end up causing constipation. Conversely, in small doses, antidepressants can improve intestinal symptoms in case of irritable bowel syndrome.

Abundant Fountain of Benzodiazepines

The human intestine is an abundant fountain of benzodiazepines, the family of psychoactive chemical agents included in drugs so popular – they are addictive – like Valium and Xanax. Why are there benzodiazepines in the gut? Certainly, because they can alleviate the states of anxiety, so that in the intestine there is an authentically pharmaceutical laboratory where occur, among others, natural drugs against stress.

On the contrary, drugs to treat intestinal problems would multiply mood disorders. The intestinal disturbances, due to an antibiotic or not, cause anxiety disorders, by the multiplication of a protein responsible for the mood.

The Human Intestine Is Also Involved in Certain Diseases That Are Not aPriori Related to the Digestive System:

* Obesity that would be due to hyperactivity of the digestive tract.

* Certain diseases or brain injuries, such as Alzheimer’s disease or Parkinson’s disease. The latter could be detected several years before the development of typical clinical signs, by lesions of the digestive system.

* Neuro-psychiatric diseases such as autism. The intestinal flora seems capable of impacting the functioning of the brain, and thus on anxiety and depression.

All autoimmune diseases are born in the human intestine. So far, nearly 200 autoimmune diseases have been discovered in traditional medicine and all of them start in the intestine: rheumatoid arthritis, arthritis, lupus, asthma, nephropathies, diabetes type 1, etc.

These links between the brain and the intestine may also explain why an anxious profile is often found in patients with irritable bowel syndrome. The impact of intestinal function on neurotransmitters and vice versa offers a functional (and not psychosomatic) explanation for the links between mood and digestion disorders.

The Human Intestine and Emotions

Thoughts, emotions, feelings, obsessions, and worries are all emotional events that are related to both the brain and the belly. If the event is considered good, it passes the psychic barrier (managed by the small intestine), otherwise, it is evacuated.

Numerous studies have shown that changes in the gut microbiota cause changes in mood and behavior. An unbalanced microbiota exacerbates anxiety, poor stress management, pain, sleep disorders, fatigue, and depressive states.

It is in the human intestine that sorting between assimilable and non-assimilable, the absorption of nutrients, and the exclusion of toxins and toxins. The evils of the digestive system speak to us of a difficulty to digest, to assimilate an experience.

The Health of the Human Intestine Starts with a Good Diet

The health of the human intestine is very important and we must take care of it, by providing the food and nutrients essential to its proper functioning. The importance of prevention requires pro-biotic and pre-biotic treatments.

Pro-biotics or dietary supplements rich in essential fatty acids, omega-3, or fiber, contribute to its protection. Probios means “for life”, and pro-biotic strains induce a multitude of positive health effects by maintaining or restoring the balance of flora.

Foods also contain substrates that nourish the good bacteria and this is the case for all fermented products such as sauerkraut, Lacto-fermented liquids.

Prebiotics, rich in Fos-fructooligosaccharides, also called oligo-fructoses – are not assimilable by the body but are digested by the intestinal flora. They promote the development of probiotic bacteria responsible for colon health. These foods include Jerusalem artichokes, chicory root, salsify, leeks, and bananas among others.

The Food Errors Are Very Quickly Deleterious on the Good Functioning of This Second Brain:

* excess protein intake,

* sweet products,

* concentrated in starch and gluten (wheat, barley, oats),

* foods are high in saturated fats (meats, industrial pastries, palm oil).

In addition, chewing and inadequate salivation is habits that can only aggravate the process. Meals taken on the run, walking, or continuing to work are not recommended.

One of the solutions is to consume food without waste, low in cellulose, as well as products resulting from organic agriculture because they contain still alive germs. Group B vitamins (especially present in vegetables), provided they are cooked al dente or steamed, to preserve them from the heat, harmful for them.

Focus as much as possible on quiet meals, even if you have little time while making sure to chew each bite.

Inappropriate diet, microbial infections, and exposure to environmental toxins are the main sources of intestinal inflammation.

Cleaning Through the Power Supply

For a week, for example, replace the morning and midday meals with juicy fruits.

This system has the advantage of cleaning the small intestine as the large colon. Because it is the residues of the food which accumulate and one finds there as well food waste as the remains of hormones of our emotions. We reduce the food load, we sweep and we find ourselves with a clean bowel.

This way of proceeding that is centered on the human intestines will also get rid of all the tensions, anxieties, depression, and all the psychic worries that have most of the time originated in the second brain.

The Human Intestine – Center of Our Vitality

The belly is the most fragile and the most generative force of our body. The strength of concentration, balance, nerve impulses and muscles, is the “Hara” in Japanese (the area just below the navel). The part above the navel (area of the solar plexus) represents vitality and energy.

Solar PlexusSolar Plexus

The solar plexus affects all organs of the abdominal region. When the solar plexus works well, the organs will not suffer from stress and tension. But when the balance is broken, the problems will be felt.

The real emotions are in the solar plexus rather than in the brain. The latter only records the memory of an emotion. Modern civilization advocates more the power of reason, cerebral reasoning, to repress emotions. This prevents the solar plexus from functioning and sets the stage for the onset of physical and psychological problems.

Taking care of the Hara exerts a healing power against nervousness, in any form. Both recent studies on the enteric nervous system and ancient knowledge of Hara suggest the appropriateness of neglecting the chatter of the mind and paying more attention to the symptoms and sensations of the stomach and intestines.

Thus one could discover conflicting emotions that should be solved or avoided the development of many diseases in their early stages. In a certain way, the adult human being should recover the wisdom of the baby, for whom the sensations that come from the belly are above almost all the others and he can desperately cry when he is hungry or caressing his belly when he arrives satisfying sensations.

The Similarities Between the Human Intestine and the Brain

The similarities between the two brains are amazing. Even the resemblance of cerebral circumvallations to that of the intestinal labyrinth, and beyond this appearance, the two brains behave in the same way when they are deprived of “entries” from the outside world.

During sleep, the brain produces 90-minute cycles dominated by slow waves and punctuated by REM (Rapid Eyes Movements) periods. Also during the night, when it has no food, the human intestine has cycles of 90 minutes of slow muscle movements, punctuated by periods of rapid movements. People with intestinal problems also have abnormal REM sleep.

The brain is characterized by its ability to learn. The colon can also do this because it can be trained: if every day is applied an enema at 10 am for a period, it is very likely that at the same time day occurs a significant bowel movement even without the need for an enema. In the treatment of irritable bowel syndrome, it seems effective to respect a schedule of visits to the toilet and in general, it is advisable to take the meals every day at the same hours.

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