Can feces be used to treat diseases? Intestinal flora has miraculous effects

Author: You Wenjuan, Editorial Director of World Science, Shanghai Institute of Science of Science

Using other people's feces to treat your own illness? In ancient times, there were records of "Huanglong Decoction" and "Poguan Decoction" using feces to treat typhoid fever, but most of them are sneered at by modern people. However, in the past decade or so, the scientific community has set off a trend of studying human feces. Is there really a component in feces that can cure diseases? In fact, what scientists are really interested in is the intestinal flora that slips out of the human body along with the feces.

Scientific studies have found that some common diseases in modern life are related to intestinal flora imbalance, such as constipation, diarrhea, obesity, etc., and even affect autism, Alzheimer's disease, Parkinson's disease, depression and other diseases. Traditional drugs are not so effective in treating such diseases, and new treatment methods and approaches are urgently needed clinically. Since there is a correlation between certain diseases and intestinal flora, will intestinal flora be a breakthrough for new treatments?

New medical breakthrough: fecal microbiota transplantation therapy

Clinical practice has brought very positive signals.

For example, there is a disease called "recurrent Clostridium difficile infection", which is a complication of infection symptoms often caused by the use of antibiotics or other drugs. Patients may suffer from diarrhea at the mildest level, or even damage to the colon or even life-threatening at the worst. Moreover, this infection often occurs in the already vulnerable group of hospitalized patients. Traditional treatments are not ideal. However, researchers have found that if the flora in the feces of healthy people is moved to the intestines of patients in a certain way, it can work wonders, and 90% of people can be cured.

Can feces transplantation cure diseases? This low-cost and highly effective treatment method has attracted researchers to explore the possibility of intestinal flora to treat more diseases. As a result, the so-called "fecal microbiota transplantation" therapy, also known as intestinal microbiota transplantation therapy, microbiota transplantation therapy or FMT therapy, has gradually emerged.

After more than a decade of development, it has been clinically confirmed that more than 80 diseases can be improved by intestinal flora therapy[i], such as constipation, irritable bowel syndrome, etc., with an efficacy of up to 65%; it is even beneficial for some psychological diseases and neurological diseases.

In view of this, many companies have smelled the potential for market application. After all, there are so many patients and even sub-healthy people waiting to use healthy poop.

As early as 2012, MIT postdoctoral fellow Mark Smith had foreseen the bright prospects and founded OpenBiome in the United States, providing stool samples for intestinal flora transplantation treatment to at least 122 hospitals in 33 states[ii].

In October of the same year, Zhang Faming, who had just returned from Johns Hopkins Hospital, also realized the potential of the market and prepared to plan to establish a fecal microbiota bank in China. His goal was to "build a microbiota bank like a blood bank, and to make microbiota transplantation as convenient, efficient and safe as blood transfusion"[iii]. The treatment concept of him and his team was "transplantation of intestinal microbiota" rather than transplantation of a certain type of strain, and they proposed the concept of "washed microbiota transplantation", which means removing unnecessary components, retaining the necessary microbiota and being able to quantify them.

In order to enhance the persuasiveness of his products and technologies, Zhang Faming personally took part in the research: he asked the team to take samples from deep in his intestines at regular intervals to provide samples for the research; in the later stages of the research, he also performed a bacterial flora transplant on himself. After this transplant, he completely solved the problem of diarrhea caused by drinking.

Of course, in addition to "washing flora transplantation", there are also "manual fecal flora transplantation" and "formulated flora transplantation technology", all of which are classified as "fecal flora transplantation". This treatment method focuses on "not producing flora, but only transporting flora".

Why can intestinal flora cure diseases?

When it was discovered that this therapy was effective for many types of diseases, everyone subconsciously realized that this therapy seemed to have a "panacea" quality... Then, curious people began to ask: What is the exact mechanism of this therapy?

Some researchers started with the neurological disease - Parkinson's disease.

Parkinson's disease is a neurodegenerative disease whose pathogenesis is still unclear. Medication can achieve a certain degree of control or relief but not a cure. The entire medical community is looking forward to new treatments.

Some researchers have discovered this phenomenon: when Parkinson's disease worsens, the patient's intestinal flora often also "oscillates". So the researchers naturally speculated whether there is some relationship between Parkinson's disease and intestinal flora.

In 2016, researchers tried to transplant patient feces into germ-free mice. As a result, these mice soon developed symptoms of Parkinson's disease, which to a certain extent confirmed that there is a definite correlation between the two.

So, what's wrong with the intestinal flora of Parkinson's patients? A study published in Nature in 2022 sequenced the fecal bacterial genomes of more than 700 subjects and found that the intestinal flora of patients was different from that of healthy people. For example: Parkinson's patients often lack a bacterium called "Prevotella". Without their help, it becomes more difficult for the human body to break down plant fiber, making it more prone to constipation. This happens to coincide with the symptom of constipation that Parkinson's patients often suffer from. (Of course, this is not the only change. The researchers also found that the number of at least two harmful Enterobacteriaceae in the patient's intestines increased.)

So, in addition to causing constipation, how does intestinal flora imbalance affect the brains of Parkinson's patients?

In fact, the human body has more than just a network of neurons in the brain, there is also a network of neurons in the inner wall of the intestine, which is called the " enteric nervous system ." Because of the existence of this system, biochemical substances secreted by the intestinal flora can affect the nervous system through this system. When studying the intestines of Parkinson's patients, researchers found that there is a substance called "curled protein" in the intestine, the main function of which is to settle (colonize) the intestinal flora on the inner wall of the intestine. At the same time, the researchers observed that once this molecule comes into contact with alpha synuclein in the intestine, the latter will misfold and aggregate. And "alpha synuclein aggregation" is a key symptom of Parkinson's disease.

But how do substances produced locally in the intestines reach the brain? For many years, scientists have speculated that the vagus nerve may be at work. Until 2017, a study published in the journal Neurology found that if the vagus nerve is cut, the risk of Parkinson's disease will decrease. This discovery confirmed the speculation.

Of course, the fact that the vagus nerve system plays a key role in such diseases does not mean that it is the only path. For example, scientists have found that substances produced by intestinal flora can also enter brain tissue through the blood, causing inflammation and damage. Therefore, if we want to start with intestinal flora to alleviate or even treat Parkinson's disease, we need to look forward to further research.

Researchers have also made important discoveries about the relationship between intestinal flora and depression.

In 2019, Yao Honghong's research group at the School of Medicine of Southeast University started with the psychological disease - depression. After they knocked out a certain gene, the mice showed depression-like behaviors, accompanied by significant changes in the intestinal flora. So far, the depression model mouse has been successfully constructed. The researchers further transplanted intestinal flora to this type of mice and found that the transplantation could avoid the problems caused by the knocked-out genes, that is, it improved the depression symptoms of the model mice. The research results were published in Gut Microbes, a well-known journal in the field of microbiology. This study confirmed the correlation between the two.

Why can intestinal flora affect depression in mice? The answer lies in the secretions of intestinal flora. In February 2022, a study led by Sarkis Mazmanian of the California Institute of Technology published in Nature found that a small molecule metabolite produced by intestinal bacteria can enter the mouse brain and change the function of brain cells, thereby causing the animal's anxiety behavior to increase.

On the other hand, a recent new study discovered intestinal flora secretions that can improve depression. In April 2024, a team led by Professor Jia Wei of the Sixth People's Hospital affiliated to Shanghai Jiao Tong University School of Medicine collaborated to discover at the molecular level that a molecule called homovanillic acid (HVA) in intestinal secretions can protect damaged hippocampal neuron function and thus relieve depression. The research results were published in the journal Cell Metabolism.

Of course, so far, the research on the relationship between intestinal flora and human body is still in its early stages. I believe that with the continuous progress of research, the deeper the mechanism of action between diseases and intestinal flora is revealed, the more effective clinical application of intestinal flora can be promoted.

[i] https://onlinelibrary.wiley.com/doi/full/10.1002/advs.202301097

[ii] https://www.boston.com/culture/health/2014/10/15/a-poop-bank-in-massachusetts-will-pay-you-40-every-day/

[iii] https://user.guancha.cn/main/content?id=695526

This article is a work supported by the Science Popularization China Creation Cultivation Program

Author: You Wenjuan, Editorial Director of World Science, Shanghai Institute of Science of Science

Review: Tao Ning

Produced by: China Association for Science and Technology Department of Science Popularization

Producer: China Science and Technology Press Co., Ltd., Beijing Zhongke Xinghe Culture Media Co., Ltd.