Feeling down? Maybe your stomach is asking for help!

Recently, the topic of "Is the stomach really an organ of emotions" has been widely discussed on Weibo. Judging from the discussion and popularity, many friends seem to have similar experiences, so what is going on?

Picture taken from Weibo

There is an English proverb: "Have butterflies in one's stomach". Directly translated, it means that there are many butterflies flying in a person's stomach. It is often used to describe a person who is extremely nervous, uneasy, and in a state of ups and downs.

I have to say that this metaphor is too vivid. However, more and more evidence proves that this statement may not be accurate enough. On the one hand, it is not just the stomach that is related to emotions, but the entire digestive tract ; on the other hand, the connection between the digestive tract and the brain is much deeper than we originally thought.

More than 100 years ago

Gut-mood connection discovered

As early as 1915, physiologist Walter Cannon wrote in The Mechanical Factors of Digestion that when animals are afraid, their stomach function changes , and similar phenomena can also be observed in humans.

On the one hand, gastrointestinal feelings can affect emotions . For example, after eating "sinful" foods that are high in sugar, salt, and calories, one will feel happy, but when hungry one will become irritable. On the other hand, emotions seem to affect gastrointestinal reactions in turn . For example, seeing things that frighten people will make one feel nauseous and vomiting, and encountering stressful things will make one feel without appetite. However, "a thousand cups of wine are not enough when drinking with a good friend", and when happy moments occur, one cannot help but have an increased appetite.

What causes these seemingly unrelated organs to interact with each other?

The discovery of the enteric nervous system (ENS) in the mid-19th century was a major scientific breakthrough in understanding the interaction between the nervous system and the digestive system.

Copyright images in the gallery. Reprinting and using them may lead to copyright disputes.

Scientists have proposed that the enteric nervous system is not unique to humans or mammals, and that its homologues can be found throughout the animal kingdom, including insects, snails, and sponges.

Thus, in order to ensure the best response (i.e., fight-or-flight response) to challenges posed by our internal environment (or, in more primitive animals, their intracavitary environment), both the ganglia of the primitive brain of roundworms and the brains of more advanced mammals may have evolved during evolution from primitive but homologous enteric neural circuits.

There are 10 billion

The intestinal system of neurons

With the development of science and technology and the advancement of research methods, this hypothesis has been further confirmed.

Different from our previous knowledge, many scientists now propose that the autonomic nervous system includes a third branch, the enteric nervous system, in addition to the familiar sympathetic and parasympathetic nervous systems. Based on its size, complexity, and similarities with the brain in terms of neurotransmitters and signaling molecules, the enteric nervous system has even been called the "second brain" .

Copyright images in the gallery. Reprinting and using them may lead to copyright disputes.

This "second brain" has more than 10 billion nerve cells distributed in the wall of the gastrointestinal tract from the esophagus to the rectum. They control our entire digestive process : swallowing food, releasing enzymes that break down food, controlling blood flow during nutrient absorption, and excretion of feces. All of these functions depend on their mutual coordination.

In the past two decades, the connection between the digestive tract and brain nerves has received increasing attention, and many related disciplines and research directions have emerged, including enteric neuroscience, neuroimaging, intestinal microbiology and host-microbe interactions, and the recent vertical branches such as microbial gut-brain signaling.

Gastrointestinal diseases

Healing with mood medication?

The above explanation may be too theoretical, so let’s look at an example.

In the gastroenterology department, there is a disease that may be considered to be more "difficult to deal with" - Irritable Bowel Syndrome (IBS). This is actually a common gastrointestinal disease, and at least 1 in 10 people in the world may suffer from this symptom.

It is a functional disease characterized by chronic abdominal pain and changes in bowel habits. It is estimated that although irritable bowel syndrome is not fatal, it will have a negative impact on the patient's life . For example, it may affect the patient's work, study and social life, and even cause mental health problems such as depression and anxiety .

It is difficult to deal with because its cause has not been identified. It may be related to the complex interaction disorder between the intestines and the central nervous system, but the specific mechanism of the disorder has not yet been clarified. On the other hand, a hundred people with irritable bowel syndrome may have a hundred different treatments. These very personalized methods include changing eating habits, increasing exercise, reducing stress and receiving psychotherapy.

In addition to conventional methods, some patients may also need to use antidepressants to alleviate symptoms .

Copyright images in the gallery. Reprinting and using them may lead to copyright disputes.

For many years, researchers and doctors believed that anxiety and depression caused irritable bowel syndrome. However, some studies have come to the opposite conclusion. Researchers have found that irritation in the gastrointestinal system, in turn, sends signals to the central nervous system, which triggers mood changes . Antidepressants may be involved in interrupting this transmission process, improving mood and gastrointestinal performance at the same time.

In addition to irritable bowel syndrome, there are other gastrointestinal diseases that require the use of psychiatric drugs. These include functional dyspepsia, functional gastrointestinal symptoms, gastroesophageal reflux disease, etc. These diseases are caused by the neural, endocrine, and immune regulatory networks and are related to mental illness, so psychiatric drugs can improve related symptoms.

The Temple of the Body

We have not yet fully explored

The more we learn about the brain-gut connection, the more we discover there is still a lot we don’t know.

Although scientists have inferred that many chronic diseases are related to the disorder of the connection between the brain and the intestinal nervous system, there is only solid evidence for a few diseases , such as functional gastrointestinal diseases, inflammatory bowel inflammation, and eating disorders (especially obesity and anorexia). More research is still exploring how intestinal activity affects human metabolism, such as whether brain-intestinal imbalance increases or decreases the risk of health problems such as type 2 diabetes? Is it related to the early onset of Alzheimer's disease?

Copyright images in the gallery. Reprinting and using them may lead to copyright disputes.

The brain-gut interaction is an emerging field, and we still have a lot to learn. The metaphor of the digestive tract as an "emotional organ" doesn't even begin to describe its specialness in the body. Of course, more often than not, thinking about how to make it feel satisfied is more pressing than understanding its complexities. For example, what should I eat tonight?

Planning and production

Author: Chen Mo'ao, Master of Epidemiology and Health Statistics

Reviewer: Tang Qin, Director and Researcher of the Science Popularization Department of the Chinese Medical Association

Editor: Cui Yinghao

Some of the pictures in this article are from the copyright library

Reprinting may lead to copyright disputes