If you are depressed one day, you should think about whether there is something wrong with your intestinal flora.

Author: Cui Yihui, registered dietitian, master of medicine

Reviewer: Zhu Wenli, Professor and Master Supervisor, Peking University Health Science Center

In medicine, depression is an affective disorder. Its typical symptoms include significant and prolonged low mood, lack of interest and pleasure, decreased will and behavior, inattention, insomnia, lack of appetite, inappropriate guilt, suicidal attempts or behaviors (the suicide rate is as high as 15%), and in severe cases, even mental symptoms such as auditory hallucinations and delusions may occur.

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In recent years, the incidence of depression has been rising in countries around the world. According to statistics from the World Health Organization, the global incidence of depression is about 11% (at least 1 in 10 people suffer from this disease). It is currently the fourth largest disease in the world and is predicted to become the second largest disease in the world after heart disease in the future. Depression may become more and more common and become the main killer of human health in the 21st century.

Faced with the menacing depression, scientists have never stopped exploring ways to curb it. The latest research results in this field show that (most people may not think of it) the bacterial community living in the intestines may be a key factor. Do you think you heard it wrong? Depression, which has always been considered a mental illness, is not only regulated by the brain, but also controlled by these small bacteria that "live under the protection of others"? In our body, in addition to a "head" growing on the neck, there is another "gut brain" growing in the stomach. The concept of "gut brain" was proposed by American scientists in the late 20th century. It refers to the second brain of the human body composed of the intestines, the enteric nervous system and the intestinal flora. Subsequently, more and more studies have confirmed that the intestinal flora can indeed affect people's emotions and behaviors through the gut-brain axis between the "gut brain" and the "head" (that is, the neural reflex axis between the flora-gut-brain).

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The messenger substances that control human emotions, neurotransmitters (5-hydroxytryptamine, dopamine, γ-aminobutyric acid, etc.) and various hormones that make people happy are mainly synthesized in the intestines, and then delivered from the "gut brain" to the "human brain", which forms the transmission of information. If the synthesis of these substances in the intestines is reduced, the transmission of information will also be reduced, and emotions will be affected.

Many animal experimental studies have shown that intestinal flora plays a key role in inducing depression and anxiety. Studies have found that patients with depression have changes and imbalances in their intestinal flora, and an increase in harmful bacteria. Therefore, more and more studies have been conducted on whether probiotics can have an effect on emotions, and many exciting results have been obtained, that is, taking probiotics can significantly improve depression and anxiety symptoms. Let us imagine the future together. Supplementing with probiotics may be an auxiliary method or new treatment for many mental illnesses, including depression. Don't think that intestinal health is only about diarrhea and constipation. That's really thinking too simply about the small bacteria stationed in the intestines. They don't have a parasitic relationship with us, but a symbiotic relationship, "prosperity and loss together".