The thought of transplanting another person’s poop into your colon may sound unpleasant, and understandably so. Feces are a smelly mixture of water, undigested food, dead and living bacteria, and other cells and substances. However, the live bacteria in feces have proven their worth in treating diseases and ailments of the digestive tract. This is why doctors have been transferring feces from healthy donors to sick patients for years—usually by colonoscopy, enema, or pill—to restore gut health.
The concept is relatively simple: Good bacteria from donated feces will colonize the patient’s gut if the recipient’s microbiome is out of balance and will outcompete any trouble-causing bacteria. For example, healthy fecal bacteria can be used to treat an infection with Clostridioides difficile bacteria, which can infect the human colon and cause mild to life-threatening diarrhea. In clinical trials, fecal microbiota transplants are estimated to be more than 90 percent effective at clearing C. diff infections. And just last month, researchers in Norway wrote in the journal Gastroenterology that patients with irritable bowel syndrome (IBS) suffer less from bloating, stomach cramps, and constipation after being treated with a fecal transplant—even three years after receiving it.
David Ong, a gastroenterologist at Mount Elizabeth Hospital in Singapore, sees even greater potential for these treatments, as gut microbes interact with our brain and other organs. Ong, who in 2014 was the first doctor in Singapore to perform a fecal transplant on a patient infected with C. diff, says recent studies suggest the intervention could also help people with inflammatory bowel disease or obesity, or those on the autism spectrum with gut problems related to picky eating. There are currently more than 100 clinical trials investigating the effect of fecal transplants on conditions ranging from depression to epilepsy and Covid-19 to cancer.
“Genes are what you’re born with, and it is what it is,” says Ong. “But the gut microbiome is something that you can manipulate. And if you can manipulate it to a good outcome in terms of disease, that’s excellent.”
There’s just the small matter of finding the right poop, though. In addition to working as a gastroenterologist, Ong cofounded the startup Amili, which houses what is currently Southeast Asia’s only fecal transplant bank. It has collected more than 1,000 stool samples over the past three years. However, most willing donors are excluded after filling out questionnaires and having their stool, blood, and saliva tested in the lab.
Lifestyle, diet, medical history—including the use of antibiotics, which can kill off gut bacteria—and how someone was born can all rule people out. (Newborns delivered through the vagina pick up their first gut bacteria from their mother as they move through the vaginal canal and show greater microbial diversity than those delivered by C-section.) In the Norwegian trial, the stool samples used to treat 87 patients with IBS came from one donor: A 36-year-old man who was born vaginally; breastfed; was a nonsmoker; had been treated with antibiotics only a few times; exercised regularly; and consumed high amounts of protein, fiber, minerals, and vitamins. Generally, once a donor is deemed healthy enough, lab technicians will examine their stool sample. The technicians are looking for diverse microbiomes and, in particular, bacteria known to compete with harmful bacteria.
Screening for suitable donors is a lengthy and expensive process, as is storing and shipping fecal samples. The largest stool bank in the US, run by the nonprofit organization OpenBiome, has stopped collecting donated samples for transplants due to financial struggles and an expectation that the US Food and Drug Administration will approve alternative treatments for C. diff.
But what if patients just used their own poop—or rather, healthy poop from their past? If harvested at a time when the patient was in good health, the bacteria in the sample would likely be well-balanced, perhaps removing the need to test and assure the quality of the donor’s stool.
In June of this year, after numerous requests from families, Amili announced that it would set up a separate bank for people who want to store their own samples for future treatments. Ong explains that individuals can freeze and preserve the “perfect version of their gut microbiome” when they are young and healthy, similar to storing eggs or stem cells, and then have them transplanted back when their health falters. “It removes a little bit of the yuck factor, as well, because you’re receiving something from yourself rather than from someone else,” he says.
Ong is not the only one who’s enthusiastic about the prospect of rejuvenating the gut microbiome using personal stool samples. Last week, researchers from Harvard Medical School and Brigham and Women’s Hospital argued in the journal Trends in Molecular Medicine that the concept is worth exploring. They point to the mild temporary adverse effects observed after transplants with donated samples, and also to the potential for disease transmission between donor and recipient, and the fact that the long-term safety of donating fecal matter remains to be studied.
Emerging research and clinical trial data suggest that all of these concerns could be avoided by patients providing their own samples. “We don’t know a lot about why this works, to be truthful, but it does appear that using your own stool is better and safer than using a random donor,” says Scott Weiss, a professor of medicine at Harvard.
But Sarah McGill, an associate professor of medicine who studies the use of fecal transplants at the University of North Carolina, foresees logistical challenges. “Stool banks, which now exist mainly to treat people with C. diff infection, typically hold stool for weeks or months. Holding samples for years or decades would be more expensive,” she says.
These high costs could deter many people. Amili plans to freeze stool samples at the facilities of Cordlife, a company that has been operating an umbilical cord bank since 2001, and store the samples there for an initial 10 years at a cost of $5,500 to the owner. Yang-Yu Liu, an associate professor at Harvard Medical School and Brigham and Women’s Hospital and a coauthor of the Trends in Molecular Medicine article, acknowledges that not everyone will be willing to pay the costs associated with rejuvenating their gut microbiome. “Similarly, not all parents would like to pay the cost for cord blood banking for their newborns. You can imagine that this will create a case of haves and have nots,” he says.
Even if people were willing and able to invest in their own poop, all the experts I spoke to say that long-term studies on this type of fecal transplant are needed to advance the field, and that these research findings won’t be available for a while. The gastroenterologist McGill notes that not only is there the issue of having to wait for recipients to need a transplant of their own stool—either because they’re ill or have grown old—but their health outcomes would have to be measured over time as well. Scientific studies could take years, if not decades. “I think we first need to establish the efficacy of donor fecal transplants in different diseases before investing in these types of studies,” she says.
Ong nevertheless sees the value of maintaining stool banks—whether for donated or personal samples—while the science is still evolving. After all, stool samples are not only needed for clinical trials and treatments, they can also tell us more about the elusive gut microbiome: how a healthy microbiome differs from an imbalanced or diseased one, and how the bacteria vary by environment and geographical location. “Whatever discoveries are made in Europe or America may not necessarily be applicable or validated in this part of the world,” Ong says, referring to Singapore. “That’s another reason why we felt a need to really do something in this area.
Updated 7-8-2022 13:15 pm ET: This story was updated to clarify that Amili has collected, not transplanted, more than 1,000 stool samples.
Updated 7-12-2022 06:00 am ET: A previous version of the article incorrectly stated that OpenBiome had stopped shipping donated samples.
