Stool Transplants

E. Coli Bacteria Is a Common Component of Stool

While the concept itself may sound repugnant, the latest data on stool transplants continues to show serious potential for the treatment of a number of medical conditions. Stool transplants or fecal microbiota transplants, are a treatment for changing a patient’s gut flora—the bacteria that live throughout the gastrointestinal tract. The technique works through collecting stool from a healthy donor. This stool is processed and then utilized by the patient, typically by enema, feeding tube or in capsules. Once implanted, if things go well, the bacteria from the donor stool begin to grow. When successful, the procedure provides a healthier population of bacteria throughout the digestive tract.

The strongest evidence of the utility, and officially, the only approved use in the United States for stool transplants, is for Clostridium difficile or “C. diff” infections. C. diff is a bacterium in the gut that can overgrow, often as a consequence of antibiotic treatment. It can cause severe, life-threatening diarrhea. Once present in large quantities, C. diff can be difficult to eliminate, often recurring after antibiotic treatment. 

The latest meta-analysis of clinical trials found that stool transplants were 82% effective for treating C. diff. Infection (Bascunana 2021). Of interest, vancomycin, the standard antibiotic treatment, was only shown to be 61% effective (Nelson 2017). As a condition with potentially severe consequences, C. diff is a serious threat in the United States. Estimates suggest 500,000 infections per year with 29,000 deaths (Turner 2019).   

While not yet approved, emerging data suggests that stool transplants may also have a place in the treatment of other conditions, including:

  • Ulcerative colitis and irritable bowel syndrome
  • Autism
  • Parkinson’s and Alzheimer’s disease
  • Type 1 Diabetes
  • Weight loss

Stool Transplants and Gastrointestinal Health

While the data on stool transplants for C. diff infections is impressive, data on treating other gastrointestinal conditions shows lower, but still useful efficacy. Ulcerative colitis, a type of inflammatory bowel disease, is a condition that often includes bloody diarrhea. In severe cases, it may become necessary to surgically remove the colon. The symptoms of ulcerative colitis usually wax and wane over time. Typically, treatment focuses on promoting and sustaining remission of symptoms (Langan 2007). 

A recent review concluded that stool transplants were of similar efficacy to standard treatments for promoting remission (Vuyyuru 2021). A separate review concluded that stool transplants were effective and safe for treating ulcerative colitis, especially when administered by enema in quantities of over 275 grams (Zhao 2020). 

Irritable bowel syndrome (IBS) is a common gastrointestinal condition that includes diarrhea or constipation with abdominal pain related to stool passage. A recent review found that stool transplants may have some utility for IBS, but the data is decidedly mixed (Wu 2022). The data suggests that the procedure may be helpful for some cases, but only when administered via a colonoscopy or endoscopy procedure. While quality of life improved, global symptoms were not changed at the one year mark with stool transplant treatment. When administered via capsules for IBS, outcomes were worse than placebo treatment for irritable bowel (Wu 2022). Due to the mixed results, more data is needed on when and how stool transplants should be utilized for IBS.

Autism and Stool Transplants

The data on stool transplants as a treatment for autism are promising. In a small initial study (Kang 2017), 16 of 18 autistic children had improvements in gastrointestinal symptoms that were mostly maintained over two years. Symptom improvements in autistic behaviors were also present in the treated children (Kang 2019). 

A small, separate study using two transplants in autistic children also found general improvements in gastrointestinal symptoms and symptoms of autism (Zhao 2019). The largest and most recent study also found similar results. In the study, stool transplants improved gastrointestinal health while reducing autistic symptoms in children (Li 2021). Considering the challenges inherent with treating autism, stool transplants appear to have some promise in reducing symptoms while improving long-term outcomes. 

Stool Transplants and Other Conditions

Parkinson’s and Alzheimer’s Disease

A Stool Transplanted to the Outdoors

While the research into using stool transplants is interesting, in many cases, the data from human trials is quite limited. Parkinson’s disease is a challenging condition that slowly destroys a person’s ability to initiate movement among other symptoms. A case series of six patients treated with stool transplants found benefits in five of six patients at two months for both movement and non-movement based symptoms (Segal 2021). 

As for Alzheimer’s disease, data has been building that shows correlations between gut flora and disease progression (Varesi 2022). While animal studies suggest benefits with stool transplants, human data is limited. However, two separate case studies found improvements in cognitive function with the use of stool transplants (Hazan 2020, Park 2021). The first case, a man with mild cognitive impairment, improved rapidly after a stool transplant for C. diff. After the transplant, the man’s cognition quickly normalized which coincided with improvements in mood (Hazan 2020).  

The second case study involved a woman with moderate dementia. After fecal transplant, her dementia symptoms began to improve. At three months, only mild symptoms of dementia remained (Park 2021). Based on these two case studies, additional clinical trials are warranted to see if stool transplants have a place in Alzheimer’s disease treatment. 

Type 1 (Autoimmune) Diabetes

A small study on type 1 diabetes also showed significant promise. Type 1 diabetes involves an autoimmune process that destroys the pancreas’ ability to produce insulin for regulating blood sugar. In early stage patients, a stool transplant halted the progression of the disease (de Groot 2021). However, it did not reverse the need for insulin. The strangest part of the results were that self transplants were effective, while stool from other donors was less so. These unexpected findings deserve additional research in other autoimmune conditions to see if self transplants might provide benefits. 

Weight Loss

Interestingly, a larger trial on weight regain after dieting found that self stool transplants were also helpful. After six months of dieting, a stool sample was collected and processed into capsules. In those taking the treatment capsules that had been on a “green-Mediterranean diet,” the capsules reduced weight regain, waist circumference and helped maintain insulin levels. The green Mediterranean diet included green tea and a green shake rich in polyphenols. The green-Mediterranean diet was the only dietary intervention in the study that changed the gastrointestinal flora, which is likely why the capsules were effective (Rinott 2021).


While there is an obvious level of disgust at the idea of stool transplants, the data suggests that they have a significant place in medicine. From being a highly effective treatment for C. diff, data also suggests potential benefits for ulcerative colitis and autism. Initial data may even indicate the utility of stool transplants for Parkinson’s disease, Alzheimer’s disease, type 1 diabetes and obesity. It’s likely that therapies for modulating gut flora, like stool transplants, will play a significant role in the future of medicine. 

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