I want to poop right after eating. What's the reason?

Not long after eating, the call of the wild from deep in your intestines is a little overwhelming. Your metabolism is so fast that you realize that the only thing between deliciousness and stench is your digestive system.

This article is reproduced from the public account "Global Science"

Written by | clefable

7 to 9 meters is not a long distance. It is the distance that fresh and juicy food travels after entering the human body. It usually takes 24 to 72 hours. 1 to 3 times a day, the food begins this journey under the action of external forces. After being squeezed in turn, it completely loses its original appearance and finally returns to the air and running water.

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Metabolism

In order to make room for new food, humans and many animals have a reflex system that regulates eating and excretion - the gastrocolic reflex. Generally speaking, when food enters the intestines from the stomach, it causes the muscles around the junction of the stomach and intestines to be stretched. At this time, the gastrocolic reflex will be activated, and people will have the urge to defecate. This reaction occurs about 15 minutes after eating, especially after breakfast or dieting. In this process, the strongest reaction is the sigmoid colon, which is piled with feces. The muscles at the upper end of the colon contract and the muscles at the lower end relax, pushing the feces to move through strong peristalsis. If all goes well, the feces will enter the rectum and then be discharged from the anus.
In order to ensure smooth bowel movements, when we eat food, we will carefully consider the combination of meat and vegetables, nutritional content, and whether the food is fresh, clean, and safe. However, if the residue is not discharged 2 to 3 days after eating the food, and stays at the end of the intestine for a long time, they will "retaliate". The most common consequence of this "revenge" is constipation.

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According to an article published in Nature Reviews Disease Primers in 2017, the average prevalence of chronic constipation worldwide has reached 14%, which is more common among the elderly, and there are more female patients than male patients. There are roughly three reasons for the formation of chronic constipation. One is that the muscles involved in defecation cannot exert force effectively and correctly, the second is that the colon does not move sufficiently, and the third is factors such as dietary changes and medication intake. All of these are related to the "second brain" in the human body - the enteric nervous system (ENS).

The second brain

The enteric nervous system is the largest autonomic nervous system in the human body, containing about 500 million neurons, five times the number of neurons in the human spinal cord. This nervous system is embedded in the lining of the gastrointestinal system, extending from the esophagus to the anus. Including the gastro-colic reflex, there are many internal microcircuits in the enteric nervous system that can transmit information using the same neurotransmitters as the central nervous system (CNS).
During the digestive process, sensory neurons in the enteric nervous system can sense mechanical force and chemical pressure, and motor neurons can regulate intestinal peristalsis through intestinal muscles; in addition, some neurons can control the secretion of mucus and hormones. According to a study published in The Journal of Physiology, the food people eat every day and every time is different. When different nutrients enter the gastrointestinal tract, they can also activate some specific sensory neurons, prompting the intestine to control intestinal movement, the amount of enzyme secretion, and intestinal permeability according to specific nutrients.

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In addition, the central nervous system also regulates the enteric nervous system through the gut-brain axis. The vagus nerve in the brain and intestine connects the central nervous system and the enteric nervous system. When the vagus nerve is cut off, although the central nervous system can still complete digestive activities independently, some hormones can replace the neural pathways to regulate the enteric nervous system, but this process is slower than neural regulation.

Scientists have discovered that the complex connection between the central nervous system and the enteric nervous system can explain why patients with some neurological diseases experience intestinal symptoms. For example, constipation is one of the most common symptoms in Parkinson's patients. Some harmful substances produced by constipation can also make the symptoms of some diseases more severe. According to a follow-up study published in npj Parkinson's Disease in 2021, the more severe the constipation, the more likely Parkinson's patients will be to experience symptoms of dementia, which means that cognitive impairment will be more severe. In addition, some studies have found that constipation may also lead to the occurrence of diseases such as Alzheimer's disease and Lewy body dementia. For example, some Alzheimer's patients may have experienced more severe constipation a few years ago.

On average, a person will excrete about 6 tons of feces in his lifetime, including water, undigested fiber, carbohydrates, lipids and proteins, in addition to rich microorganisms. The longer the feces stay in the human body, the more microorganisms will degrade the proteins in it, producing some toxic byproducts such as ammonia, hydrogen sulfide, histamine, thiols and indoles. Once these substances pass through the intestines and enter the blood vessels, they may enter the brain through the blood. They will poison neurons, and in the long run, they may cause cell death and cognitive impairment. A golden rule to avoid these problems is to respond to the call of the body and don't hold it in.

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If you move too fast

In addition, there is another situation. At some points, we can feel the sound of rapid peristalsis of the intestines, and the urge to defecate comes very suddenly and cannot be restrained. These symptoms mean that we are experiencing diarrhea. Under normal circumstances, diarrhea will only last for 1 to 2 days. If it lasts for more than 2 days, it may be worth being particularly vigilant, because it is likely caused by pathogenic bacterial infection (including Escherichia coli, Salmonella, etc.), viruses (including rotavirus, norovirus and adenovirus, etc.) or parasites (dysentery amoeba).

When harmful bacteria invade the human body, they will multiply in the intestines to produce toxins or invade intestinal cells, which will cause intestinal inflammation and lead to diarrhea. Among them, unhygienic drinking water or food is a common cause of such problems. In addition, some diseases can cause long-term chronic diarrhea, such as irritable bowel syndrome and chylomicronism. Some studies have found that the gastrointestinal walls of patients with irritable bowel syndrome are particularly sensitive. When stimulated by water, food, etc., gastro-colonic reflexes may occur, leading to emergency situations. Many patients will experience intestinal pain for a long time, and suffer from symptoms such as dehydration and malabsorption. In some serious cases, it is also necessary to ask a doctor for help in time.

This article comes from the WeChat public account "Global Science"