Digging up the roots | Is the gastrointestinal tract an emotional organ? Will not eating well make you "stupid"? The answer is beyond many people's expectations!

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We all know the importance of the stomach and intestines. They have the important task of digesting food so that the body can smoothly absorb the required energy and substances.

But have you ever wondered why our emotions sometimes affect our stomachs? Or why we feel unhappy when we have indigestion?

You may think, isn't this normal? Who can be happy without eating enough? But some studies have shown that unhappiness is not just because of unsatisfied appetite. The gastrointestinal tract can directly affect emotions. It is not just a simple digestive organ. It also has a surprising role: as an emotional organ, it affects our emotions and cognitive abilities.

Therefore, the topic #It turns out that the stomach is an organ of emotions# once became a hot search, sparking widespread heated discussion, and many people said they couldn’t believe that "the stomach and intestines are organs of emotions."

Weibo screenshot

So, is the stomach an organ of emotion? How does it affect our emotions and cognitive abilities?

This article will take you to explore the magic of the intestines as an organ of emotions and understand the new role of the gastrointestinal tract!

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The gastrointestinal tract is the second brain

Two-way connection with the brain

Our gastrointestinal tract is a miraculous system that has about 600 million neurons[1], a surprising number that is almost the same as the number of neurons in a cat’s brain. These neurons can autonomously regulate the digestive function of the intestine without the control of the brain, so the gastrointestinal tract is known as the “second brain” of the human body[2].

The picture below allows us to have a more intuitive understanding of the nervous tissue of the gastrointestinal tract.

From reference [2]: Adult small intestine myenteric plexus, with aggregates of neurons and glia in mature ganglia and numerous neurites within and between ganglia.

This “second brain” has a complex and subtle connection with our main brain, the brain, forming a system that scientists call the “gut-brain axis.” In this system, the brain and gastrointestinal tract can transmit information to each other, allowing the brain to affect the function of the gastrointestinal tract, and at the same time, the gastrointestinal tract can in turn affect the function of the brain, including our emotions [3].

This two-way communication between the gut and the brain can occur via four main pathways[3]:

▶ Nervous system, including the enteric nervous system and vagus nerve

▶ Neuroendocrine and Hypothalamic-Pituitary-Adrenal Axis (HPA Axis)

▶ Immune system

▶ Neuroactive compounds from microbes

Let’s take an example.

Neurotransmitters are the mediators that transmit signals between nerves, and our intestinal flora can also produce these neurotransmitters, such as GABA, dopamine, and serotonin. These neurotransmitters not only affect the neurons in the intestine itself, but can also send signals directly to the brain through the blood circulation [3,4].

From reference [3]: Dynamic communication in the gut microbiota-brain axis

Our emotions can affect the function of the intestines. For example, when we are upset, we may feel a loss of appetite, which is what we often call "full of qi"; some people may experience diarrhea or constipation when they are angry or excited.

So, how does the gastrointestinal tract affect our emotions and cognition?

Next, I will reveal this mysterious process to you.

The Mood Mystery: How Does the Gastrointestinal Tract Affect Emotions?

The gastrointestinal tract affects our emotions in two main ways.

1

Gut flora and mood

The gut microbiota is a vast world of microorganisms that thrive in our intestines in surprisingly large numbers.

It is estimated that there are about 1,000 different species of microorganisms in the intestines, totaling a staggering 100 trillion [5]. These microorganisms are not only involved in maintaining the normal function of the intestine, but also affect our mood to some extent.

As early as 1998, scientists discovered in experiments that oral administration of subclinical doses of Campylobacter jejuni to rats (a dose that would not cause infection) caused the rats to exhibit anxiety-like behaviors. Later studies confirmed that the cause of this behavior was that the bacteria activated neuronal areas in the brain that depended on information received from the intestines via the vagus nerve [6].

The effects of this bacteria on mood have also been demonstrated in humans. For example, one study found that adults who were stressed or exhausted experienced a 40.7% improvement in their general condition after taking a combination of Lactobacillus acidophilus, Bifidobacterium bifidum, and Bifidobacterium longum for six months[7].

From reference [7]

In addition, scientists have also found differences in the intestinal flora of healthy people and patients with depression. In the intestines of patients with depression, the relative abundance of Firmicutes, Actinobacteria, and Bacteroidetes changed significantly [5].

So how do intestinal flora affect our emotions? It turns out that the human vagus nerve responds to microbial signals, cytokines, and intestinal hormones (such as serotonin). Changes in the intestinal flora itself and the cytokines they produce can send signals to the hypothalamus-pituitary-adrenal axis through the vagus nerve, thereby affecting human emotions [5,8].

2

Gastrointestinal inflammation and mood

Inflammation in the gut is another important factor that affects mood. Inflammation has been shown to play an important role in mood disorders such as depression, and people with depressive symptoms often show increased expression of pro-inflammatory cytokines.

When our gastrointestinal tract is in a bad state, such as gastroenteritis, irritable bowel syndrome, etc., it will release more inflammatory substances; at the same time, the permeability of the intestine will also increase, allowing these inflammatory factors to enter the blood circulation and thus affect our brain function [5,6].

Some scientists even believe that intestinal inflammation itself can lead to neuroinflammation, promoting microglial activity and triggering the guanine pathway[5], which is associated with many mood disorders such as depression and mania.

Current studies have found that anti-inflammatory drugs such as COX-2 inhibitors are effective for major depression, which also confirms the role of inflammation in depression[6].

These are two important mechanisms of how the gastrointestinal tract affects our mood through gut flora and inflammatory responses.

How does the gastrointestinal tract affect our cognition and intelligence?

Will people become stupid if they have a bad stomach?

This question may sound a bit exaggerated, but in fact, in addition to affecting emotions, gastrointestinal health is indeed closely related to our intelligence and cognitive abilities.

1

Gut microbiota and brain development

You may never have thought that our brain development requires the help of our gastrointestinal microbiota from the very beginning.

While we are still in our mother’s womb, gut microbial metabolites such as serotonin from our mother may cross the placenta to the growing fetus and influence the fetal brain development[9].

The role of the gut microbiota in the brain does not end once the baby is born. They also synthesize vitamins essential for human survival, such as vitamin B12[9], which is one of the basic substances required for neural development and myelination.

From reference [9]: Communication between the gut microbiota and the brain during prenatal and postnatal development.

2

The impact of intestinal flora on intelligence and cognition

Studies have found that the types and quantity of intestinal microbiota are closely related to our intelligence and cognitive abilities. People with specific intestinal microbial genera tend to have higher cognitive abilities and intelligence, and also have a protective effect on the brain's intelligence and cognition.

A study based on the Guangzhou Nutrition and Health Study (GNHS) population found that people with mild cognitive impairment had a higher number of Firmicutes in their intestines, while the normal group had a relatively higher number of Bacteroidetes (Figure b, c). Bacteroidetes is believed to be associated with better cognitive performance (Figure e).

From reference [11]

In another study [12], the University of Bonn in Germany analyzed the intestinal flora of 40 adults to determine their fluid intelligence, that is, the ability to process and learn new information, solve problems, and pay attention to and manipulate the environment. They also found that specific genera, such as Clostridium 5, were positively correlated with these abilities. That is, the more Clostridium 5 there was, the stronger these abilities were.

Scientists are also studying whether changes in the intestinal flora can be used to detect changes in brain cognition. Perhaps we can detect Alzheimer's disease in advance, a disease that causes great pain to patients and their families.

When scientists studied Alzheimer’s disease model mice, they found that the intestinal flora of model mice showed differences from those of normal mice when they were young (1-3 months old). However, the typical changes of Alzheimer’s disease - amyloid deposition - only appeared in small amounts at 3 months old, and obvious amyloid plaques were observed at 6 and 9 months old [13].

Therefore, after reading this, I believe everyone has realized the importance of intestinal health. Intestinal health is affected by many factors such as diet, lifestyle and emotional management, so it is necessary for us to take comprehensive measures to maintain gastrointestinal health. This can not only help us maintain a happy mood, but also help improve our intelligence and cognitive abilities.

Tips for better gastrointestinal health:

Feed your stomach and nourish your mood

First of all, we should promote a balanced diet

Diet is the source of the substances our body needs and has an impact on all systems of the body, so try not to be biased in terms of food. The "Dietary Guidelines for Chinese Residents (2022)" recommends a balanced diet with a variety of foods and reasonable combinations, and try to have more than 12 kinds of food a day and more than 25 kinds of food a week.

You can eat more vegetables, fruits, whole grains, and dietary fiber, which are beneficial to the intestinal flora, so that the intestines can function better. At the same time, you can reduce some foods that have negative effects, such as high-fat foods, which increase inflammation and are not conducive to building a good mood. [5]

Secondly, positive attitude towards life and emotional management

Emotions and gastrointestinal health are two factors that influence each other, so managing emotions is also an essential factor for gastrointestinal health.

You can learn to actively cope with stress, such as through meditation, relaxation techniques, yoga and breathing exercises, which can help relieve tension and anxiety and reduce gastrointestinal discomfort. In addition, cultivating an optimistic attitude towards life and communicating more with family and friends can also help alleviate negative emotions and promote gastrointestinal health and emotional stability.

Finally, moderate exercise and physical and mental relaxation

Exercise is not only good for physical health, but also has a positive effect on intestinal function. Moderate exercise can promote intestinal peristalsis, help food pass through the digestive tract smoothly, and prevent constipation and other problems.

In summary, the stomach is not just a simple digestive organ, it plays an important role in our emotions and cognitive functions. By understanding the new role of the intestine as an emotional organ, we can take better care of it, maintain gastrointestinal health, and improve mood and intelligence.

By maintaining a balanced diet, a positive attitude, moderate exercise, adequate sleep and stress management, we can cultivate healthy intestinal flora, improve digestion, enhance emotional stability, and enhance intelligence and cognitive abilities. Gastrointestinal health and emotional stability are the cornerstones of our pursuit of physical and mental health and a happy life.

in conclusion

The stomach is the think tank of emotions, and gastrointestinal diseases can affect our emotions and even our nervous system. In addition, gastrointestinal health is closely related to our intelligence and cognitive abilities, which means that not eating well may really make you stupid!

Therefore, let’s “feed our stomachs and nourish our moods” and move towards a healthier, happier and wiser future together!

Author: Mr. Ayuan, an internist

Reviewer: Liu Jianbing, Associate Professor, Xiangya Hospital, Central South University

References:

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[2]Avetisyan M, Schill EM, Heuckeroth RO. Building a second brain in the bowel. J Clin Invest. 2015;125(3):899-907.

[3]Gwak MG, Chang SY. Gut-Brain Connection: Microbiome, Gut Barrier, and Environmental Sensors. Immune Netw. 2021;21(3):e20.

[4]Ahmed H, Leyrolle Q, Koistinen V, et al. Microbiota-derived metabolites as drivers of gut-brain communication. Gut Microbes. 2022;14(1):2102878.

[5]Limbana T, Khan F, Eskander N. Gut Microbiome and Depression: How Microbes Affect the Way We Think. Cureus. 2020;12(8):e9966.

[6]Appleton J. The Gut-Brain Axis: Influence of Microbiota on Mood and Mental Health. Integr Med (Encinitas). 2018;17(4):28-32.

[7]Gruenwald J, Graubaum HJ, Harde A. Effect of a probiotic multivitamin compound on stress and exhaustion. Adv Ther. 2002;19(3):141-150.

[8]Faraj J, Takanti V, Tavakoli HR. The Gut-Brain Axis: Literature Overview and Psychiatric Applications. Fed Pract. 2021;38(8):356-362.

[9]Al-Asmakh M, Anuar F, Zadjali F, Rafter J, Pettersson S. Gut microbial communities modulating brain development and function. Gut Microbes. 2012;3(4):366-373.

[10]Liang X, Fu Y, Cao WT, et al. Gut microbiome, cognitive function and brain structure: a multi-omics integration analysis. Transl Neurodegener. 2022;11(1):49.

[11]Oluwagbemigun K, Schnermann ME, Schmid M, et al. A prospective investigation into the association between the gut microbiome composition and cognitive performance among healthy young adults. Gut Pathog. 2022;14(1):15.

[12]Oluwagbemigun K, Schnermann ME, Schmid M, et al. A prospective investigation into the association between the gut microbiome composition and cognitive performance among healthy young adults. Gut Pathog. 2022;14(1):15.

[13]Chen Y, Fang L, Chen S, et al. Gut Microbiome Alterations Precede Cerebral Amyloidosis and Microglial Pathology in a Mouse Model of Alzheimer's Disease. Biomed Res Int. 2020;2020:8456596.

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