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By Mary Carpenter
“WHAT about trying a fecal transplant?” one guest asked New York painter E.N. at a resort lunch last summer. By 2024, the topic of transferring donor stool samples (fecal microbiota transplantation, or FMT) to treat intestinal problems—currently approved only to treat dangerous, recurring infections of C.diff (clostridium difficile)—had become (slightly) more acceptable for mealtime conversations.
“The “ick” factor of getting a poop transplant doesn’t faze many of my patients who are desperate to vanquish their gut health woes,” writes Harvard gastroenterologist Trisha Pasricha in the Washington Post. Pasricha notes that, by transplanting healthy bacteria—that make up a healthy microbiome —via “healthy poop to an unhealthy gut, we can alleviate certain illnesses, but so far, our hopes have gotten ahead of the data.”
“The human microbiome is like a garden, where [many variables] affect whether you get weeds or beautiful flowers,” writes Pasricha. Because hormonal, dietary and neuronal factors affect the microbiome differently in each host, she said, “we still aren’t sure what combination . . . will give one individual weeds or flowers [the reason a 2019 meta-analysis of trials on patients with irritable bowel syndrome] “did not show a benefit of fecal transplant . . . there is no single microbial abnormality present in all patients.”
In addition to using FMT to treat C.diff—delivered in recently approved medications either orally or via colonoscopy—physicians have studied and prescribed it off-label for obesity, for several autoimmune GI conditions and for irritable bowel syndrome ( IBS), an array of GI complaints that can be hard to diagnose. Slate described one review of IBS research involving almost 500 patients that found FMT relieved some symptoms, but results were not statistically significant.
Even for C.diff, when the pandemic led to the suspension of FMT research at the University of Michigan, program director Krishna Rao treated patients with longer than normal courses of antibiotics and “leaned into holistic care (e.g. encouraging patients to eat fermented foods, which have anti-inflammatory effects),” according to the American Society of Microbiology. When 90% of these patients got better, Rau concluded that not all patients need FMT—but it’s impossible ahead of time to determine which ones do.
Three current targets of the NIH-based Human Microbiome Project—charged with establishing a database of microbial communities from 300 healthy individuals—are onset of type 2 diabetes and Irritable Bowel Disease, an autoimmune condition; and pre-term birth. For off-label uses, anything other than for C.diff, physicians obtain samples from stool banks, the largest being OpenBiome—while HumanMicrobes acts as donor network for those choosing the DIY route.
“The ultimate donor is probably something like a 2-to-18-year-old Michael Jordan,” according to HumanMicrobes; as well as someone less likely to have taken antibiotics. Before collecting and stool samples, OpenBiome screens donors so extensively, founder Majdi Osman told Slate, that qualifying is more difficult than getting into Harvard.
But even with careful screening, donor stool can contain unhealthy bacteria or unknown pathogens. Mpox (monkeypox), for example, “before the onset of the 2022 global outbreak . . . was circulating in the population—and stool banks and clinicians didn’t know about it,” according to the American Society of Microbiology. And improper screening for E.coli at a hospital-based stool bank may have caused the death of an immunocompromised 73-year-old man.
The greatest risks of FMT stem from the effects of the enormous influential gut microbiome—which can change from day to day—on everything from GI functioning to mood disorders. Conversely, risks also stem from frequent, outsized changes in the gut caused by food, hormones and brain activity—as well as medications: for example, using statins to lower LDL levels can make the gut more receptive to some bacteria, and less to others. Explains psychopharmacogeneticist Sony Tuteja at the University of Pennsylvania, “It could be bidirectional. The microbiome is affecting the drug, and the drug is affecting the microbiome.”
And differences in individuals’ microbiomes can alter, sometimes dangerously, the effects of prescription drugs: of 1,000 drugs screened in a 2018 study, nearly one-quarter had antibiotic effects in the gut despite not being sold as antibiotics. With medications such as those used to treat Parkinson’s disease, molecules in the gut can increase or decrease the amounts that reach the brain.
“It was possible to essentially transplant a mood disorder into rats,” according to Nature writer Neil Savage, on studies at APC Microbiome Ireland. “The ability of certain good bacteria to synthesize neurotransmitters . . . mood-regulators such as serotonin—may explain the link between low diversity of gut microbes and mental health conditions.”
A diverse diet is the number one recommendation of Netflix’s “Hack Your Health: The Secrets of Your Gut” —that is, consuming 20-30 fruits and vegetables each week. The second is to eat much higher levels of fiber than in the current American diet. “Your microbiome loves fiber,” writes Pastricha. Over years of eating too little fiber and taking too many antibiotics, she explains, “subsequent generations lost huge groups of microbes that could not be fully recovered.”
Supplemental psyllium is another component of Pastricha ‘s advice—starting with a low dose of 10 grams daily to as high as 30 grams, split between morning and evening doses—“that responds in real time to your bowel needs: it provides bulk to stool when you have diarrhea but can also retain water, which softens up your poop when you’re constipated. “
While most people—including painter E.N.—are unwilling to try FMT, others with persistent debilitating symptoms have gone the DIY route. D.C. area resident 66-year-old Alexandra, profiled by Slate, suffered from cystitis, candidiasis and irritable bowel syndrome, as well as frequent urinary tract infections and “terrible acid reflux.” Using preparations from HumanMicrobes, costing about $1,500, Alexandra started with a frozen stool sample that didn’t help much, and then tried capsules with “even worse” results.
“Finally…something miraculous happened and she got better,” according to Slate. “My body was distressed about taking all these new microbes,” Alexandra concluded, “but it got to the point where the microbes were established.” HumanMicrobes founder Michael Harrop acknowledges that many factors might have played a role in Alexandra’s improvement—including the placebo effect—but he also posed the question: “What if there is a miracle drug waiting for us in the right toilet?”
—Mary Carpenter regularly reports on topical subjects in health and medicine.
