Is the stomach an emotional organ? Why does stress cause stomach problems?

Produced by: Science Popularization China

Author: Flower Tea (Qingdao Agricultural University)

Producer: China Science Expo

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In modern society, stress seems to be our shadow, everywhere. Exams, work, family, all kinds of pressure make people breathless. Sometimes, when we face stress - such as tomorrow's exam, the speech that is about to start, the report to the leader - at this moment, in addition to headaches and insomnia, our stomachs may "protest" and have diarrhea, abdominal pain and other discomfort symptoms, and we can't help but run to the bathroom.

The culprit behind this may be a disease called irritable bowel syndrome with diarrhea (IBS-D). Why does stress cause diarrhea? Recently, a study published in the journal Cell Metabolism has revealed the mystery of how stress triggers IBS-D.

Article title image

(Image source: Cell official website)

Pressure multiple transmission diarrhea

Before revealing the relationship between the two, let’s first understand diarrhea-predominant irritable bowel syndrome, which is a common disease that affects the colon digestive system, manifested as abdominal pain, bloating and diarrhea. Its causes are complex, including bacterial infection, improper diet, genetic factors and psychological stress. If abdominal discomfort suddenly occurs when facing stress, it is generally believed that stress-induced IBS-D occurs, that is, stress affects the contraction of intestinal muscles, changes the function of the digestive system and defecation, but the specific mechanism is still unclear.

Stress causes gastrointestinal discomfort

(Photo source: veer photo gallery)

Scientists used a chronic restraint stress program - locking mice in a small tube so that they could not turn around but not overly squeezed. After a period of time, in such a "stifling" environment, the mice would develop a chronic stress response. In layman's terms, this "successfully" caused the mice to bear tremendous psychological pressure, leading to behavioral disorders and obvious intestinal dysfunction.

The study found that the intestinal tissue of mice underwent varying degrees of changes, including the length of the distal intestinal villi, the height of the crypts, the various cells in the intestine, and the differentiation ability of intestinal stem cells were also different from the normal state, and even the mitochondrial morphology had changed.

So scientists began to dig further into the culprit that caused this problem and found that psychological stress affects the number and metabolism of lactobacilli in the intestines. The results showed that indole-3-acetate (IAA) increased 3-5 times compared to normal levels. IAA is actually a metabolite produced by lactobacilli in the intestines.

Under normal circumstances, Lactobacillus is a good friend in our intestines, helping us digest food. However, researchers have found that when we feel stressed, the number of Lactobacillus in the intestine increases, and the IAA they produce also increases, which destroys the mitochondrial function of intestinal stem cells (ISCs), affects the differentiation of ISCs, and ultimately leads to damage to the intestinal epithelial barrier. In short, IAA makes our intestinal cells "sick."

"Intestinal stem cells are key to intestinal health. These cells are responsible for the self-repair and renewal of the intestine and maintain the integrity of the intestinal barrier. However, when IAA is present, they cannot function properly and the intestinal barrier is compromised."

Coincidentally, another study found that stress can cause the body to produce too much xanthine, which in turn changes the number and metabolism of Lactobacillus in the intestines. The spermidine produced by Lactobacillus inhibits the baseline expression of type I interferon (IFN-α) in dendritic cells, leading to limited contractile function of colon smooth muscle cells and increased bowel movements.

The study first evaluated the psychological state of IBS-D patients and found that their anxiety scores and frequency increased significantly. At the same time, experiments with mice confirmed that psychological stress can induce IBS-D-like symptoms. Previous studies have shown that stress can cause CD4+T cells to produce a large amount of xanthine, which can cause anxiety. This study found that serum xanthine levels in IBS-D patients and stress model mice were also increased, and intraperitoneal injection of xanthine can directly induce IBS-related symptoms.

The research team also found that imbalance of intestinal flora plays an important role in IBS-D. Lactobacillus murine is upregulated in multiple mouse IBS models, and this bacterium can directly induce IBS-related symptoms.

Through a series of experiments, scientists revealed how Lactobacillus murinus inhibits dendritic cells from producing IFN-I through spermidine, thereby affecting the contractile function of colon smooth muscle cells. This provides a theoretical basis for the pathological mechanism of stress-induced IBS-D and a new direction for therapeutic drug targets.

Relaxation is the key

How to solve the above problems?

The good news is that scientists have found a possible "antidote" - α-ketoglutarate (α-KG), which can be taken orally to promote the recovery and differentiation of intestinal stem cells and compensate for damage. It is like putting on a "protective suit" for intestinal stem cells to protect them from IAA damage.

The researchers analyzed the fecal flora composition of patients with major depression and found that the abundance of Lactobacillus and IAA levels in patients with depression were significantly increased compared with healthy controls. This suggests that the above mechanism may also exist in humans, and α-KG may really be a good intestinal remedy.

Of course, the impact of stress on the body is huge and widespread, and this study may only reveal the tip of the iceberg. The researchers plan to continue exploring the upstream effects, analyzing how the brain issues instructions when facing stress, and the safety and effectiveness of α-KG.

Relax your mind and be healthier

(Photo source: veer photo gallery)

Studying the correlation between stress and diarrhea has enhanced our understanding of intestinal health and the mechanism of stress-induced IBS-D, and will also help find solutions. We can adopt a variety of treatment strategies for IBS-D symptoms, including drug therapy, such as α-KG, and enhancing the function of immune factors such as IFN-α to relieve symptoms. In addition, we can change the composition of intestinal flora and reduce the excessive growth of Lactobacillus by adjusting diet and supplementing probiotics.

Of course, individuals also need to learn to adjust their mental state and master stress management techniques, such as meditation, yoga, and deep breathing, to reduce the negative impact of stress on the intestines. If the condition is too serious, professional institutions need to intervene and use psychological treatments such as cognitive behavioral therapy to deal with stress and improve intestinal symptoms. Maintaining mental health is also an important step in protecting intestinal health.