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Donating your blood could save someone's life. And so could donating your poop.

Correction: The writer for this episode was actually Hannah Thomasy, who is wonderful.

Hosted by: Michael Aranda

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[ ♩ INTRO ♩ ].

Donating your blood or bone marrow could save someone’s life. So, too, could donating your poop.

And if you’re among the 3% of prospective donors that makes the cut, you could be paid $40 a pop—or a plop, I guess—to donate your feces. It’s not really the poop doctors are after, but the bacteria in it, so that they can perform fecal microbiota transplants or FMTs. Scientists are currently exploring how FMTs can help fight disease by altering the community of microbes in a person’s gut.

But early results suggest they could help with a surprising number of things, from infections to autoimmune disorders. If you want to donate your turds, you’re going to have to talk to a stool bank, like the one operated by the nonprofit OpenBiome. And they do pay, if your poop can pass muster.

But they’re super picky about their donations. That’s in part because there are a lot of infections that can be transferred from an. FMT, some of which can exist in a healthy person without causing symptoms.

So potential donors must have poop, blood, and nasal swabs tested for dozens of bacteria, viruses and parasites both before and after they donate. But the main reason is that scientists aren’t sure exactly what can be transmitted via the microbes in your poop. And preliminary research says it could be… a lot.

Differences in the community of gut bacteria, or microbiome, have been linked to a remarkable variety of diseases, though scientists don’t know yet if those links are causal. So, to be on the safe side, potential poop donors must be screened using a rigorous interview process to ensure they’re basically disease and disorder-free. If all is clear, then you could be cleared to make several donations a week for a couple months.

And from there, readying the transplants is pretty simple: just a quick filtering step to remove any chunks before they’re frozen and shipped out to clinicians. The actual transplanting part can happen several different ways. The most direct route is up the rectum with an enema or colonoscopy device, but sometimes a nasoenteric tube is used instead.

That’s a tube inserted through the nose that goes all the way down into the intestines. The newest method, though, is to have the goods packaged into capsules that patients can swallow like normal pills. These are less invasive, and preliminary studies suggest they may still be as effective as more traditional methods.

Which is great, because as scientists continue to connect microbiomes to disease conditions, the potential for using FMTs as treatments increases exponentially. Right now, the most common use is for treating Clostridium difficile infections. Clostridium difficile – or C. diff – is a bacterial species that can exist in your gut even when you’re totally healthy.

The trouble comes from the fact that it’s often resistant to antibiotics. So if you take an antibiotic when you already have C diff, the drugs can knock out competing bacteria, allowing it to take over. And that’s really bad because the bacteria produce a toxin that can cause severe diarrhea, and in some cases, even lead to kidney failure or tears in your intestines.

These aren’t small complications—the bug is associated with 29,000 deaths per year in the US alone. Luckily, FMT is amazing at treating it. When antibiotics fail, an FMT is usually effective in about 90% of cases.

But curing C diff infections is likely just the beginning. Some doctors think that many autoimmune diseases—conditions where the body basically attacks itself—may be triggered or worsened by an imbalanced microbiome. So getting a fresh batch of bacteria from someone with a healthy microbial community could help re-balance things.

And that seems to be the case with ulcerative colitis—a painful autoimmune condition where your bowels are prone to ulcers because they’re basically always inflamed. Though it wasn’t a perfect cure, a meta-analysis of 16 small trials found that FMT induced remission in about 30% of patients. Other studies in animal models have suggested that FMTs may be useful in treating or preventing all sorts of diseases, from Parkinson’s disease, to obesity, or even colon cancer.

But… some doctors — and many patients — have been slow to accept FMT as a viable treatment option. And…. I get it.

It does have a pretty big ick factor, and even with rigorous testing, it’s still possible that a pathogen could be transferred from one person to another. It would be great if we could just throw the right mix of microbes together to make a fake fecal microbiome of sorts—but this is no easy task. So far, scientists have identified over 2,000 species of microbes that live in our guts.

And for many, we’re still not sure whether they’re helpful or harmful or basically neutral. Luckily, doctors might not need to understand each and every species to create an artificial transplant mix—they’d just need to find the ones necessary to fix a microbiome that’s out of whack. And that’s exactly what the team behind rePOOPulate — which is an absolutely perfect name — are trying out.

Their stool substitute contains 33 species of bacteria which were originally cultured from a healthy person’s poop. And although RePOOPulate hasn’t been tested on humans yet, it did help protect mice against. C diff infection.

But, until it’s run through a battery of safety and efficacy tests, FMTs will continue to be done the old fashioned way. And while that’s a little gross, these transplants are worth further study, because the amazing microbes in your poop could hold the key to treating diseases in disorders that have doctors stumped. Though — as with any experimental treatment — you definitely don’t want to try this one at home.

Thanks for watching this episode of SciShow! If you want to learn more about your feces, you might like our episode on why your poop is sometimes green. [ ♩ OUTRO ♩ ].