Even before our era, the intestine was considered an important organ, which was compared to the gates of heaven or hell for the human body. Hippocrates discovered the connection between the quality and duration of a person’s life with the condition of his intestines. “The death of a person begins with his gut,” said the scientist.
Endocrinologist, Candidate of Medical Sciences Lilit Egshatyan* told Social Navigator about the important role of microorganisms inhabiting the intestines.
— Lilith Vanikovna, was Hippocrates right in assigning such an important role to intestinal microorganisms?
- Right. And the great Russian scientist Ilya Ilyich Mechnikov, more than 100 years ago, formulated classical ideas about the role of microflora and the nature of the relationship between them and the macroorganism. He said: “Premature and painful aging of a person depends on the poisoning of certain microbes of the intestinal flora, and everything that prevents intestinal putrefaction should improve health and delay old age.” Mechnikov also suggested that “it is possible to prolong life through surgical removal of the colon from the body.”
However, despite this, the important role of the intestines for the human body was unknowingly ignored for many decades. The intestine was considered only an organ for transporting and distributing food and removing its remains. Increased interest in its study has been observed in recent years, which is associated with the development of modern molecular genetic research methods - high-throughput parallel sequencing. Unlike traditional methods, using this technique it was possible to evaluate the qualitative and quantitative characteristics of microorganisms and their interaction with the macroorganism, that is, humans.
— What do scientists currently know?
— The amount of data accumulated to date indicates the important role of microbial cells, collectively called microbiota, in the functioning of the macroorganism. Researchers have found that the human body contains at least more than 100 trillion microbial cells with a total weight of more than two kilograms, despite the fact that a bacterial cell is lighter than air.
Out of every 10 cells in the human body, only one cell is actually human, and the remaining nine cells are microorganisms. The genome of these bacteria contains hundreds of genes (more than 100 times more genes than in the human genome) with high metabolic activity of bacterial cells. Colonization of the intestine occurs even before birth, during intrauterine development. By the end of the first year of life, the composition of the intestinal microbiota approaches the flora of an adult and fully corresponds to that by two and a half years.
- Is this really so? It is believed that children are born with sterile intestines.
- Yes it is. The presence of microbial rRNA in the placenta, amniotic fluid, umbilical cord blood and meconium of newborns indicates colonization of the intestine before birth.
The gut is the second brain
— What role do these bacteria play?
— Bacteria help digestion, participate in the development of intestinal immunity, preventing colonization by pathogens, they participate in the synthesis of hormones, biologically active substances, vitamins, and protect the body from toxins, carcinogens, and allergens.
— There is a thesis that microbiota can influence a person’s mood. This is true?
— Yes, bacteria affect the psycho-emotional behavior of the host.
Today, the intestines are also called the second brain. Numerous experimental and clinical studies support the relationship between the gut microbiota and the central nervous system.
Studies have shown that consuming probiotics, which are beneficial microbes, significantly improves a person's mood. And infection of experimental mice leads to an increase in their anxious behavior.
One of the main functions of the intestinal microbiota is the breakdown of fiber, since it is not digested by enzymes in the human gastrointestinal tract. As a result of this process, metabolites are synthesized, these are short-chain fatty acids that affect all metabolic processes, the immune system and, consequently, mood and behavior. It has been experimentally shown that administering butyric acid (one of the forms of these acids) to mice increases stress resistance and improves mood.
— How does a person influence the state of his own microbiota?
— Microbiota is a kind of indicator of a macroorganism, responding to physiological, dietary, climatic and geographical factors by changing its qualitative and quantitative composition. Of course, there are common and divergent interests between bacteria and the macroorganism. One of the main factors influencing the composition of the intestinal microbiota and human health is nutrition or certain dietary preferences.
- For example?
— It has been revealed that over the past 30 years, since the Western lifestyle has become widespread, for example, in Japan, the prevalence of chronic inflammatory bowel diseases has increased 100 times. And this is not the result of a genetic predisposition to these diseases, but of changes in diet, including reducing the consumption of algae and switching to a European type of diet with a predominance of animal fats and proteins.
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— That is, by changing your diet, you can influence the state of the microbiota. Probably, it is possible to influence the fat content in the body, which is what everyone is worried about now, without getting out of the gym?
— The World Health Organization has declared obesity an epidemic. The avalanche-like increase in the prevalence of obesity served as the basis for the hypothesis about its infectious nature.
Experiments were conducted on mice that showed that neither a genetic predisposition to obesity nor a high-calorie diet leads to the development of obesity in germ-free mice. And introducing microbiota from obese mice to these germ-free mice resulted in a 60% increase in adipose tissue mass over two weeks, without any changes in diet. The development of obesity in animals also occurs when they are infected.
Gut microbiota tends to be similar among members of the same family, as the dietary preferences of one influence the food intake of others, leading to an increase in the number of bacteria adapted to that diet.
A decrease in the diversity of microbiota composition is also influenced by the “Western diet,” or a diet poor in dietary fiber, since in the absence of fiber in the intestine, there is a loss of certain bacteria and their genes that break down fiber. The decrease in diversity leads to an increase in the number of "bad" bacteria, which absorb more calories from the food a person consumes, which leads to an increase in fat tissue mass. With increased diversity or rich microflora, bacteria use resources for competition and cooperation, rather than for manipulation of the host.
Experiments on mice have shown that low species composition is inherited, and even when a large amount of fiber is returned to the diet, not all taxa (groups of microorganisms) are restored, and this ability decreases with each subsequent generation. Statistics in humans show that in every second obese child, one of the parents has a fat metabolism disorder, and in 1/3 both parents are obese or overweight. Thus, if choosing cake instead of fiber has become habitual, then you have most likely already spoiled the health of your descendants.
Numerous studies have discovered antibodies to various microorganisms in organs and the adipose tissue itself.
Currently, there is even a term “microbial obesity”, which was coined by microbiologist Patrick Kani. According to his research, obesity can be "contagious" when "obesity" bacteria are transmitted from person to person.
It was found that the risk of developing obesity increases by 57% in one of the friends if the other is obese. Therefore, we can discuss what obesity is - a social or infectious disease?
— How can “obesity” bacteria be transmitted?
— Back in 1982, the development of obesity during a viral infection in albino mice was described. In humans, it has also been found that a certain adenovirus (the causative agent of acute respiratory viral infections) can lead to the development of obesity. However, obesity has many causes and in most cases is caused not by a virus, but by lifestyle.
Although the literature discusses the possible impact of simple hand washing on weight control, there is no need to be afraid that you can get infected from your obese friend/relative. It is impossible to become infected with obesity, in the classical sense of the term, since there are no “easy ways” of transmitting “obesity” bacteria from person to person. The dominant pathway is the influence of one's dietary preferences on another's food intake.
In 2013, in Russia, we (scientists from the Federal State Budgetary Institution "State Scientific Research Center for Medicine", State Budgetary Educational Institution of Higher Professional Education RNRU named after N.I. Pirogov "Russian Gerontological Scientific and Clinical Center", Federal State Budgetary Institution "Research Institute of Physics and Chemistry") conducted a study, the purpose of which was to study the characteristics of the composition of the microbiota intestines depending on the nature of nutrition in patients with different metabolic status. In the course of our work, we identified bacteria that were associated with impaired carbohydrate metabolism, obesity, chronic inflammation, atherosclerosis, and so on. An interesting fact was that bacteria that were associated with type 2 diabetes mellitus affected carbohydrate metabolism disorders even when consuming less carbohydrates and fats compared to healthy people. Our results, like global ones, point to the existence of “more efficient” bacteria, the presence of which already increases the risk of metabolic disorders, regardless of diet.
— What do experts advise on how ordinary people can monitor the state of their own microbiota?
“Until we can better understand the contribution of bacteria and the interactions between individual taxa, increasing microbial diversity in the gut will be a more effective influence on host health.”
Scientific and popular articles discuss various measures to prevent “diseases of civilization.”
Early prevention. Of course, for the normal development of microbiota, the following are important: natural childbirth; early breastfeeding; breastfeeding for the first four to six months of life; in the absence of milk from the mother, the use of adapted formulas.
Nutrition. Throughout life, an important factor is dietary restrictions, the inclusion of dietary fiber in the diet (consuming an average of 30 grams of dietary fiber per day helps prevent many diseases - from cardiovascular to intestinal), as well as the consumption of natural fermented milk products, pickled vegetables, and so on. .
Refusal of self-medication. Therapy should be prescribed by a doctor and only as indicated. Uncontrolled antibiotic therapy “just in case”, firstly, leads to the formation of resistance to therapy, which is already a global problem, and secondly, it increases the risk of developing metabolic disorders. Taking two or more courses of antibiotics has been shown to increase the risk of developing diabetes.
Probiotics(“culture of specific life of microorganisms”). Despite the positive results of using probiotics, you need to understand that there are no clear criteria for which strain of bacteria you need to improve the diversity of the composition. Each person’s intestines contain a unique composition, and taking a probiotic may not always have a positive effect on the body. The study of the effect of probiotics on the microbial composition is at the stage of speculation; therefore, they should also be taken only on the recommendation of a doctor, since individual selection of the drug is required.
Prebiotics, that is, indigestible compounds that stimulate the growth of beneficial microbes are more preferable, since in this case there is no need for strict individual selection of the drug, they are resistant to the effects of gastrointestinal secretions, they are easy to store and, most importantly, restore their own microbiocenosis.
Fecal microbiota transplantation. It has been proven that this technique gives good results and eliminates the root cause of inflammatory bowel diseases. It is believed that microbiota transplantation can be used to correct metabolic disorders and restore lost bacterial diversity. The few studies of fecal transplantation for obesity have shown good results with proper donor selection. However, to date there are no standard screening criteria for selecting the “ideal” donor, which may be a potential cause of negative results as well as transmission of infections.
— How can a fecal microbiota transplant be performed technically?
— The first therapeutic use of fecal microbiota transplantation was in 1958 for inflammatory bowel disease. For intestinal diseases, various routes of administration are used: through a nasogastric tube, during esophagogastroduodenoscopy, colonoscopy, rectal enema, and so on. The choice of route of administration depends on the type and anatomy of the disease. There are no data on which route of administration is most effective for the treatment of metabolic disorders and obesity. Therefore, in 2010, acid-resistant gel capsules were created that do not dissolve in the stomach and feces were packaged in these capsules. However, there is also the problem of proper freezing for the survival of beneficial bacteria.
Therefore, it is obvious that maintaining homeostasis and normal metabolism is impossible without restoring the diversity of normal associations of intestinal microorganisms. The results of numerous studies suggest that with the help of an appropriate diet and lifestyle changes, the composition of the microbiota can be positively influenced. Despite the identified effect of various drugs, further research is needed to objectify the therapy.
Interviewed by Evgeny Eremkin
The second human brain is not the back or bone marrow, but a formation that a person has in his gastrointestinal tract. It resembles a real brain so much that it can rightfully be called a “second brain.” Some have no doubt that this brain is involved in human intellectual activity. In any case, this conclusion can be reached as a result of the achievements of neurogastroeterology. The creator of this discipline is Michael Gershon from Columbia University. It was found that in the folds of tissue lining the esophagus, stomach, and intestines, there is a complex of nerve cells that exchange signals using special neurotransmitter substances. This allows this entire complex to work independently of the brain, just as the brain is capable of learning. Like the brain, this brain is nourished by “glial” cells, has the same cells responsible for immunity, and the same protection. The similarity is enhanced by neurotransmitters such as serotonin, dopamine, glutamate, and the same neuropeptide proteins.
This amazing brain owes its origin to the fact that the most ancient tubular ancestors had what is called a “reptilian brain” - a primitive nervous system, which, in the process of increasing complexity of organisms, gave rise to creatures with a brain whose functions are extremely diverse. The remaining relic system was transformed into a center that controls the activity of internal organs, and, above all, digestion.
This process can be traced in the development of embryos, in which the initial clot of cells at the early stage of formation of the nervous system is first divided, and one part is transformed into the central nervous system, and the second wanders around the body until it ends up in the gastrointestinal tract. Here it turns into the autonomic nervous system; and only later both these systems are connected with the help of the vagus - a special nerve fiber.
Until recently, it was believed that this tract was simply a muscular tube with elementary reflexes. And no one thought to look carefully at the structure, number and activity of these cells. But later they were surprised that their number was approximately one hundred million. The vagus is not able to ensure the close interaction of this complex complex with the brain, so it became clear that the gastric brain works autonomously. Moreover, we feel its activity as an “inner voice”, as something that we are able to “feel with the liver”.
It should be noted that such an autonomous system is no exception for the body, but it is distinguished by the exceptional complexity and development of connections and the presence of those chemical compounds that are so characteristic of the brain.
The main function of this brain is to control the activity of the stomach and the digestion process: it monitors the nature of food, regulates the speed of digestion, accelerating or slowing down the secretion of digestive juices. It is curious that, like the brain, the gastric brain also needs rest and plunges into a state similar to sleep. In this dream, the stages of rapid sleep are also distinguished, accompanied by the appearance of corresponding waves and muscle contractions. This stage is remarkably similar to the stage of normal sleep during which a person dreams.
During stress, the gastric brain, like the brain, secretes specific hormones, in particular, excess serotonin. A person experiences a state when “cats are scratching at his soul,” and in the case of a particularly acute condition, the stomach becomes overexcited and “bear sickness” appears - diarrhea from fear.
Doctors have long had the term “nervous stomach”, when this organ reacts to strong irritations with especially severe heartburn and spasm of the respiratory muscles. With further action of an unwanted stimulus, at the command of the brain, substances are released into the stomach, causing inflammation of the stomach and even ulcers.
The activity of this amazing brain also affects the activity of the brain. This, in particular, is expressed in the fact that when digestion is disrupted, signals are sent to the brain that cause nausea, headaches and other unpleasant sensations. Obviously, this is also the reason for the allergic effect on the body of a number of substances.
This brain is also capable of forming conditioned reflexes. So, in one of the clinics for the paralyzed, a punctual nurse carefully gave the patients enemas at a certain time - at 10 o'clock in the morning. His colleague who replaced him after some time decided to carry out this operation only when obvious constipation occurred. But the next morning, at 10 a.m., the stomachs of all patients emptied themselves.
It is possible that it is the reaction of the gastric brain that explains nightmares when overeating. It remains to be seen what role this brain plays in the thinking process.
The second brain is in the gut
At the beginning of the twentieth century, the Englishman Newport Langley calculated the number of nerve cells in the stomach and intestines - 100 million. More than in the spinal cord! There are no hemispheres here, but there is an extensive network of neurons and auxiliary cells where all sorts of impulses and signals circulate. An assumption arose: could such a cluster of nerve cells be considered a kind of “abdominal” brain?
Recently, professor of neurogastroenterology Paul Enck from the University of Tübingen spoke on this matter: “The brain of the abdomen is structured in approximately the same way as the brain. It can be depicted as a stocking covering the esophagus, stomach and intestines. The same tissue damage found in the stomach and intestines of people with Alzheimer's and Parkinson's diseases as in the brain. That’s why antidepressants like Prozac have such an effect on the stomach.”
But all these facts are only indirect confirmation of the paradoxical hypothesis. In order for an army of neurons to turn into something like a brain, it must be organized. There is no clear evidence of this organization yet.
Professor of neurogastroenterology David Wingate from the University of London believes that the human “abdominal” brain is a descendant of the primitive nervous system of tube worms. During evolution, the “abdominal” brain did not completely disappear. This is not an atavism at all, but an important organ for those mammals whose embryos develop in the mother’s womb. Who knows, maybe this is the “inner voice” that connects mother and child?
A professor of physiology from the University of California, Emeren Mayer, proves through a series of experiments that if the brain is responsible for thoughts, then the “abdominal” brain is responsible for emotions. Any sensations, all glimpses of intuition are based on a real basis. The stomach, like the head, accumulates experience and is guided by it in practice.
Does it follow from this that the stomach is involved in intellectual activity? The gift of thinking has not yet been attributed to the stomach, but the ability to self-learn is not denied. Maybe we need to “listen” to our stomach more often?
In turn, apparently, there is a direct and reliable road between the brain and the digestive nerve center. One of them became agitated, but the other immediately became disordered. The main bridge connecting the two centers is vagus, or nervus vagus. Thousands of thin fibers extend from it into the nervous enterosystem of the digestive tract.
As La Stampa writes (translation on the website Inopressa.ru August 2005), Professor Michael Gershon believes that a person has two eyes, two arms, two legs and two brains: one pulsates in the head, the other actively operates in the stomach.
The professor is a world celebrity: he heads the department of anatomy and cell biology at Columbia University in New York, is considered one of the fathers of the emerging discipline of neurogastroenterology and is searching for new methods for studying humans.
If the mystics, and after them the others, have always emphasized the opposition “brain - body,” then Gershon refutes everyone, asserting a strange thing: brain 1 and brain 2 are autonomous units, but are in constant contact.
A decade after the publication of the most popular work “The Second Brain,” an American scientist confirms the assumption that the intestinal nervous system is not a stupid accumulation of nodes and tissues that carry out the commands of the central nervous system, as the old medical doctrine says, but a unique network capable of carrying out complex processes on one's own.
It is noteworthy that the intestines continue to function even when there is no connection with the brain and spinal cord. The number 2 brain independently handles all aspects of digestion throughout the gastrointestinal tract - from the esophagus to the intestines and rectum. At the same time, it uses the same tools as the “noble” brain: a whole web of neural chains, neurotransmitters and proteins. Evolution demonstrates its insight: instead of forcing the head to brutally strain the work of millions of nerve cells to communicate with a remote part of the body, it chose to entrust control to a center located in the zones it controls.
And just like brain number 1, the second brain, Gershon argues, is a vast data bank in which millions of years of experimentation have preserved numerous behavioral programs, ready to take action depending on the situation, in other words, digestion: whether we are talking about bun, about a full dinner, unusual food or a strict diet. The “second” brain always knows how to respond, activating the right enzymes and extracting nutrients to better nourish the body.
The stomach's secret weapon for running at high speed is the well-known neurotransmitter, serotonin. Quite unexpectedly, it turned out that almost all serotonin, 95%, is concentrated in the intestines, where it acts with maximum efficiency. The digestive process begins only when special cells (enterochromaffin) absorb it into the intestinal wall, which reacts thanks to seven receptors and transmits the order to the nerve cells to release enzymes and cause them to circulate.
Serotonin is also a messenger that informs the brain about what is happening in the stomach. Another discovery was that 90% of information comes in one direction
. Transfer occurs almost always down up, and more often than not the messages are bad. This, for example, happens with the common syndrome of indigestion, which affects every third person. And in this case, as with depression, one of the reasons is a change in the amount of neurotransmitter volume: excessive instead of insufficient. It is the fault of the molecule that is supposed to transport it, “sert”: in many people it does not function properly.
With the new discovery, Gershon notes, new therapeutic options open up for psychiatrists and gastroenterologists.
Natalya BEKHTEREVA, academician
Many peptide and protein forms are formed in the intestines, which are directly related to the activity of the brain. Poor functioning of the stomach and intestines causes depression, which is known to all ulcer sufferers. Perhaps, among the internal organs, the intestines are most connected with the brain. Alzheimer's and Parkinson's diseases fit into peptide concepts. The hypothesis about the existence not of individual nerve cells, but of neural networks in the abdominal cavity must be carefully tested.
Second human brain- this is not the back or bone marrow, but the formation that a person has in his gastrointestinal tract.
It resembles a real brain so much that it can rightfully be called “ second brain". Some have no doubt that this brain is involved in human intellectual activity. In any case, this conclusion can be reached as a result of the achievements of neurogastroeterology.
The creator of this discipline is Michael Gershon from Columbia University. It was found that in the folds of tissue lining the esophagus, stomach, intestines, there is a complex of nerve cells that exchange signals using special substances-neurotransmitters. This allows this entire complex to work independently of the brain, just as the brain is capable of learning. Like the brain, this brain is nourished by “glial” cells, has the same cells responsible for immunity, and the same protection. The similarity is enhanced by neurotransmitters such as serotonin, dopamine, glutamate, and the same neuropeptide proteins.
This amazing brain owes its origin to the fact that the oldest tubular ancestors had what is called a “reptilian brain” - a primitive nervous system, which, in the process of increasing complexity of organisms, gave rise to creatures with a brain whose functions are extremely diverse. The remaining relic system was transformed into a center that controls the activity of internal organs, and, above all, digestion.
This process can be traced in the development of embryos, in which the original clump of cells at the early stage of formation of the nervous system is first divided, and one part is transformed into the central nervous system, and the second wanders around the body until it ends up in the gastrointestinal tract. Here it turns into the autonomic nervous system; and only later both these systems are connected with the help of the vagus - a special nerve fiber.
Until recently, it was believed that this tract was simply a muscular tube with elementary reflexes. And no one thought to look carefully at the structure, number and activity of these cells. But later they were surprised that their number was approximately one hundred million. The vagus is not able to ensure the close interaction of this complex complex with the brain, so it became clear that gastric brain works autonomously. Moreover, we feel its activity as an “inner voice”, as something that we are able to “feel with the liver.”
It should be noted that such an autonomous system is no exception for the body, but it is distinguished by the exceptional complexity and development of connections and the presence of those chemical compounds that are so characteristic of the brain.
The main function of this brain is to control the activity of the stomach and the digestion process: it monitors the nature of food, regulates the speed of digestion, accelerating or slowing down the secretion of digestive juices. It's interesting that both brain, stomach also needs rest and falls into a state similar to sleep. In this dream, the stages of rapid sleep are also distinguished, accompanied by the appearance of corresponding waves and muscle contractions. This stage is remarkably similar to the stage of normal sleep during which a person dreams.
During stress, the gastric brain, like the brain, secretes specific hormones, in particular, excess serotonin. A person experiences a state when “cats are scratching at his soul,” and in the case of a particularly acute condition - stomach becomes hyperexcited and “bear sickness” appears - diarrhea from fear.
Doctors have long had the term “nervous stomach”, when this organ reacts to strong irritations with especially severe heartburn and spasm of the respiratory muscles. With further action of the unwanted stimulus at the command of the brain in stomach substances are released that cause inflammation of the stomach and even ulcers.
The activity of this amazing brain also affects the activity of the brain. This, in particular, is expressed in the fact that when digestion is disrupted, signals are sent to the brain that cause nausea, headaches and other unpleasant sensations. Obviously, this is also the reason for the allergic effect on the body of a number of substances.
This brain is also capable of forming conditioned reflexes. So, in one of the clinics for the paralyzed, a punctual nurse carefully gave enemas to patients at a certain time - at 10 o'clock in the morning. His colleague who replaced him after some time decided to carry out this operation only when obvious constipation occurred. But the next morning, at 10 am stomachs All patients emptied spontaneously.
It is possible that it was the reaction gastric brain nightmares caused by overeating are explained. It remains to be seen what role this brain plays in the thinking process.
The intestines are terribly underrated. Do you think all it can do is digest food and create food bolus? It's actually taller, cleaner and better than this! The intestines are a real superhero of the body, which, along with the brain, is responsible for a million important things, including our mood, complexion and performance.
So what can he do?1. The intestines control our emotions, and poor nutrition can cause anxiety and neuroses.
Research has shown that some microorganisms are capable of producing the neurotransmitter gamma-aminobutyric acid (GABA). It is one of the most abundant signaling molecules in the nervous system. It controls the parts of the brain responsible for emotions and the limbic system. Many anti-anxiety drugs—Valium, Xanax, and Klonopin—target the same signaling system, mimicking the effects of GABA.
2. Our diet in childhood determines whether we will suffer from obesity after 30 years.
The human intestinal microbiome, which is formed in the first two and a half to three years of life, is designed to remain that way throughout life. Figuratively speaking, the child’s body is like a symphony orchestra, in which each type of intestinal bacteria plays its own instrument.
3. The entire complex process of digestion is controlled by the intestines using a built-in “computer”.
Digestion is largely controlled by the enteric nervous system (ENS), an amazing network of 50 million nerve cells that lines the entire gastrointestinal tract, from the esophagus to the rectum. This “second brain” is smaller than the first, that is, the head, whose weight ranges from 1000 to 2000 g, but it copes brilliantly with everything related to digestion.
4. The food tract reflects any emotions that occur in the brain.
When you are seething with indignation, finding yourself in a traffic jam, the brain sends a set of signals to the gastrointestinal tract and facial muscles. They also react sharply to incoming signals. When you are angry at the driver who cut you off, your stomach begins to contract vigorously, which leads to an increase in the production of hydrochloric acid and a slowdown in the process of removing the omelet you ate for breakfast. This causes the intestines to contract and release mucus and digestive juices. Much the same thing happens when you are anxious or upset. Essentially, the digestive tract reflects any emotions that arise in the brain.
And finally, a small sketch from the book by Emeran Mayer about what your gut, that little superhero, does for you every day. Doesn't he deserve admiration?
Imagine that you went to a restaurant. The waiter brings you a well-done steak, and you start eating with pleasure. Here's a quick rundown of what happens the minute you put that first bite of steak in your mouth, although it may not be a topic you want to discuss at the table.
Even before you chew and swallow the first bite, your stomach will be filled with hydrochloric acid, which can be the same concentration as that in a battery. And when a partially chewed piece of steak enters the stomach, the acid will begin to grind it into tiny particles.
At the same time, the gallbladder and pancreas prepare the small intestine to begin work by introducing bile and other digestive enzymes that help digest fats and complex carbohydrates. When small pieces of steak pass from the stomach into the small intestine, enzymes and bile convert them into nutrients, some of which the small intestine can absorb and then pass on to the rest of the digestive tract. As food is digested, the muscles in the intestinal walls contract rhythmically (a process called peristalsis), moving food down the gastrointestinal tract.
The strength, duration and direction of peristalsis depend on the type of food eaten: it takes more time to digest fat and complex carbohydrates, and less time to process a sweet drink. At the same time, some parts of the intestinal walls contract, directing digested food to the mucous membrane of the small intestine, where nutrients are absorbed. In the large intestine, powerful peristaltic waves move food pulp (chyme) back and forth, extracting and absorbing up to 90% of its water. Finally, another powerful wave of compression moves the contents towards the rectum, usually causing the desire to have a bowel movement.
Between meals, various waves of contraction (called the migrating motor complex) occur as the digestive tract performs its motor functions. During this period, he puts things in order like a housewife, removing everything that the stomach could not dissolve or divide into small enough fragments: for example, medications that did not completely dissolve and pieces of peanuts. Every 90 minutes, this contractile wave moves slowly from the esophagus to the rectum, creating enough pressure to crack the nut and move unwanted microorganisms from the small intestine to the large intestine. Unlike the peristaltic reflex, the housecleaning wave occurs only when there is no longer any food left in the gastrointestinal tract to digest (for example, during sleep). The “gastrointestinal tract cleaning mode” turns off the moment you put the first piece of food into your mouth at breakfast.
Illustration: Shutterstock
Not only the brain, but also the gastrointestinal tract is involved in a person’s mood, decision-making and behavior. The human body has a separate nervous system that is so complex that it is called the second brain. It consists of approximately 500 million neurons, and is about 9 meters long and runs from the esophagus to the anus.
It is this “brain” that may be responsible for eating junk food during stress, mood changes and some diseases.
Enteric Nervous System - Your “second brain”
The walls of the gastrointestinal tract contain the enteric nervous system (ENS), which was previously thought to be involved exclusively in controlling the digestive process. Now experts suggest that it plays an important role in a person’s physical and mental state. It can work autonomously and interact with the brain.
If you look inside the human body, it will be difficult not to notice the brain and the branches of nerve cells along the spine. The ENS, a wide network of neurons located in two layers of intestinal tissue, is less noticeable, which is why it was discovered only in the middle of the 19th century. It is part of the autonomic nervous system, a network of peripheral nerves that control the functions of internal organs.
For many years, people believed that the gut interacted with the brain to influence a person's health.
In addition to controlling the mechanical mixing of food in the stomach and coordinating muscle contractions to move food through the gastrointestinal tract, the ENS also maintains the biochemical environment in various parts of the gastrointestinal tract, thereby maintaining the proper pH level and chemical composition necessary for the functioning of digestive enzymes.
However, there is another reason why the ENS needs so many neurons - eating is fraught with danger. Bacteria and viruses that enter the gastrointestinal tract with food should not take over the body. If a pathogen penetrates the intestinal mucosa, immune cells will begin to secrete inflammatory substances, incl. histamine, which is recognized by ENS neurons. The second brain either triggers diarrhea, or tells the brain to cleanse itself in another way - through vomiting (or both processes occur simultaneously).
For many years, people believed that the gut interacted with the brain to influence a person's health. However, it was possible to confirm such a connection relatively recently, when it became clear that the ENS can act autonomously, as well as with the discovery of its main communication channel with the brain - the vagus nerve. In fact, about 90% of the signals transmitted along the vagus nerve come not from above (from the brain), but from below (from the ENS).
The second brain - the feel-good factor
The second brain has many common features with the first - it also consists of various types of neurons and auxiliary glial cells. It also has its own equivalent of the blood-brain barrier, which maintains the stability of the physiological environment. The second brain also produces a variety of hormones and about 40 neurotransmitters of the same classes as those produced in the brain.
Interestingly, about 95% of the serotonin in the body comes from the ENS.
What are the features and functions of the ENS?
- Dopamine is a signaling molecule associated with feelings of pleasure and the reward system. In the intestines, it also functions as a signaling molecule that transmits messages between neurons and, for example, coordinates the contraction of the muscles of the colon. Serotonin, which is produced in the gastrointestinal tract, enters the blood and is involved in the restoration of damaged liver and lung cells. It is also essential for normal heart development and the regulation of bone density.
- Mood. Obviously, the gut brain is not responsible for emotions. However, theoretically, neurotransmitters produced in the gastrointestinal tract can enter the hypothalamus. Nerve signals sent from the gastrointestinal tract to the brain can actually affect mood. A 2006 study published in The British Journal of Psychiatry found that vagus nerve stimulation may be effective in treating chronic depression.
- Butterflies in the stomach are the result of blood flowing back to the muscles as part of the fight-or-flight response triggered by the brain. However, stress also increases the production of ghrelin, which, in addition to increasing hunger, reduces anxiety and depression. Ghrelin stimulates the release of dopamine by acting on neurons involved in pleasure and reward pathways, as well as through signals transmitted through the vagus nerve.
Experts believe that problems with the ENS are associated with various diseases, so the second brain deserves much more attention from scientists. Controlling obesity, diabetes, Alzheimer's and Parkinson's diseases, and other diseases are potential benefits of further study of the ENS.
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