Faecal transplants and the importance of a healthy gut flora 

Can a healthy person’s gut flora be used to cure diseases? This is what scientists are trying to work out by studying how faecal microbiota transplants (FMT) can be used to repair damaged gut flora. While the method looks promising, more studies are needed to map out areas of application, and the risks and benefits.


FMT can repair damaged gut flora

FMT stands for ‘faecal microbiota transplantation’. By transplanting faecal matter from a person with healthy, thriving gut flora, damaged gut flora can get a boost of good bacteria that will help to restore the balance. There are several benefits to faecal transplants, increased bacterial diversity being one of them. Another is that this treatment does not trigger an immune response and is safer than a lot of other types of organ donation.


An ancient method that also occurs in nature

In nature, it is common for animals to eat their own or other animals’ droppings. These animals are called coprophages. By eating faeces, their gut flora both in their mouth and in the gut itself is renewed, an activity that has been shown to help improve their digestion. Meanwhile, veterinarians have been practising transfaunation, the transfer of droppings between different species, for centuries.

Faecal transplantation into humans is a technique that was first used in Chinese medicine 1,700 years ago – long before anybody knew anything about the existence of bacteria. In the Western world, the method received some attention in 1958 when a scientific paper was published, but it wasn’t until the 1970s that the method became widespread.


As a treatment for CDI

Modern-day faecal transplants are mainly nowadays predominantly in the treatment of Community-Acquired Clostridium Difficile Infection (CDI). CDI is an infection caused by the Clostridioides difficile bacteria which normally occurs in many people’s gut flora without causing any problems. The disease only arises when the bacteria have been given room to grow extensively, which usually occurs as a result of a course of antibiotics that have upset the balance of the flora in the gut. CDI can be life-threatening, but faecal transplantation has been shown to be effective where continued treatment with antibiotics has failed.


Not without its challenges and risks

One challenge with FMT is finding suitable donors. Due to the lifestyle that a lot of people in the Western world have adopted, including industrially processed foods and low amounts of fruit and vegetables, approximately 40% of the diversity of the gut flora has disappeared compared to that of our ancestors. This makes it difficult to find donors who have the right composition of bacteria in their gut flora. There is also a risk, albeit small, that the patient may become infected with diseases from the donor’s faeces. Another problem with FMT is that both patients and hospital staff often find it a psychologically stressful treatment, precisely because it involves faeces.

There are synthetically produced alternatives, such as dietary supplements that add good bacteria, which are similar to faecal transplantation but without the aforementioned drawbacks. Lactic bacteria supplements can reduce the risk of the harmful bacteria having room to multiply. Studies have also shown that people who have been given dietary supplements with lactic bacteria after a course of antibiotics had a stronger and more robust gut flora than those who did not receive any supplements with new bacteria.


Promising results with other health conditions

Because FMT has been successful as a treatment for CDI, researchers have started to take an interest in whether the method could be used for other health conditions, such as depression, asthma, allergies, IBS or diabetes. Many researchers believe that there is a connection between these diseases and imbalances in the gut flora.

The results are promising, but so far there is not enough scientific evidence to state definitively that the method can help combat conditions other than CDI. However, plenty of research is underway in the field. One of the most important jobs for these researchers is to gain a greater understanding of what ordinary flora looks like in a healthy person, what microbes it contains and how they interact with one another.


What will the FMT of the future look like?

Faecal transplants are a method that Professor Stig Bengmark discusses in his column “Poop: The best cure?”, as well as in his chapter in the book Inflammation: From Molecular and Cellular Mechanisms to the Clinic (2017). Stig’s prediction is that the method could be more effective in the future: ‘The logical choice would be to find donors among people who still live the way our forefathers did, and who have a large and varied ‘poop organ’. Maybe someday, frozen poop from the South American Yanomami people, from the Hadza, or from Burkina Faso, where people live like our forefathers and have between 20-40% more types of bacteria to offer, will be a commodity? Maybe ‘synthetic poop’ – a composite created in a laboratory to be similar to poop – is a solution?’



Bengmark, Stig. Bajs botar bäst.

Bengmark, Stig. (2017). Inflammation: From Molecular and Cellular Mechanisms to the Clinic, First Edition. John Wiley & Sons, Ltd.

Biazzo M, Deidda G. Fecal Microbiota Transplantation as New Therapeutic Avenue for Human Diseases. J Clin Med. 2022 Jul.

Hedlund, Fredrik. (2017). Goda bakterier: Hellre mångfald än enfald. Karolinska institutet. 

John Hopkins Medicine. (n/a). Fecal Transplant.

The Microbiome Health Research Institute. (n/a). About FMT.

Wenjie Zeng, Jie Shen, Tao Bo, Liangxin Peng, Hongbo Xu, Moussa Ide Nasser, Quan Zhuang, Mingyi Zhao, Cutting Edge: Probiotics and Fecal Microbiota Transplantation in Immunomodulation, Journal of Immunology Research, vol. 2019.


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