The Science of Fecal Transplants for Pain

What if poop could treat chronic pain? I'm not joking. As much as that question might sound comedic, it's very serious and scientifically legitimate. Pain comes in many different flavors. Obviously, if you smash your hand in a car door, or stub your toe, or burn your finger in a campfire, or get bitten by a parrot, which has happened to me on at least 3 occasions, it hurts. But there's another more mysterious type of pain, called nociplastic pain. Nociplastic pain isn't caused by tissue damage. It comes from dysfunctional nerve signaling. It's like the boy who cried wolf of pain, only in this circumstance, the body keeps reacting to every false or exaggerated cry of pain, over and over again. Just chronic exaggerated pain. Now, the most common nociplastic pain condition is called fibromyalgia. Maybe that's a term you've heard, but can you define it? Can you define fibromyalgia? Probably not. In fact, nobody can. It's one of those fluffy diagnoses that doctors sometimes assign when they can't pinpoint exactly what's wrong with a patient, but they want to give them some label. In fact, when I asked ChatGPT about fibromyalgia, Here's what I had to say. The running joke in medicine is that fibromyalgia is a diagnosis you give when you don't know what's wrong. It's often said half-seriously because fibromyalgia lacks definitive lab tests or imaging findings, leading some, some doctors to view it as a wastebasket diagnosis. But new research is flipping that joke on its head. It turns out there might be a potential pathophysiology and a potential solution for patients dealing with fibromyalgia and other chronic pain disorders. And it all starts in the gut. In a study published in the journal Neuron, researchers built on earlier reports that fibromyalgia patients have a distinct microbiome and metabolic signature. So to explore whether there's a causal connection between the microbiome and chronic pain, they transplanted microbiomes using poop samples from patients with fibromyalgia or from healthy control patients into mice. And here's where things get really wild. The mice adopted not just the microbiomes of their human donors, but also their pain profiles. Mice that received fibromyalgia microbiomes showed heightened pain responses to mechanical stress, heat, cold, and even displayed spontaneous out-of-the-blue pain. Now, if you're curious, and I hope you are, you may be wondering how they measured pain in mice. They used many different validated tests, but to give you just a flavor of how scientists go about measuring what's truly a subjective experience, let me explain one test they used called the Von Frey test, also called the Von Frey Filament Assay. It's a classic method used to measure mechanical pain sensitivity in animal models. In simple terms, it tests how much force it takes for a mouse or other animal, actually including humans, to react to a touch stimulus. Here's how it works. Mice are placed on a mesh floor, and researchers approach the mice from below. And a series of fine calibrated nylon filaments called Von Frey hairs are used. Each filament applies a different a precisely known amount of force when it's bent. A filament is gently pressed against the underside of the mouse's paw until it bends, and researchers watch for withdrawal of the paw or flicking or licking or some rapid jerk, all signs that the mouse felt the stimulus as painful or irritating. And a lower threshold means the mouse is more sensitive to touch. It feels more pain. It has higher pain. So you can see here in the graph below the Von Frey test results from mice given fibromyalgia microbiomes, FM in red, versus healthy control microbiomes, HC in blue. Those given the fibromyalgia microbiomes had a much lower pain threshold. They felt more pain. Hopefully that makes sense, and you can tell me in the comments if this methodological aside was worth your time. Anyway, back to our main story. To reiterate, the mice that received the fibromyalgia microbiomes showed heightened pain responses to mechanical stress, heat, cold, and even displayed this spontaneous pain. And at first, the mice didn't show any anxiety or depression-like behaviors over the course of 4 weeks. But by 4 months, they did. They showed depressive-like behaviors. Now, I bring this up, this is informative, because around 40% of human patients with fibromyalgia experience depression. Raising an important question: Does mental health decline trigger a pain disorder, or does the pain disorder fuel mental health problems? It is a little bit of a chicken and egg scenario, but these preclinical data suggest that chronic microbiome-driven pain can pave the way for depression over time. No surprise there, really. For people living with fibromyalgia and other chronic pain conditions, Life can feel like a constant battle against an invisible fire, a fire others can't see. Pain with no clear cause, treatments that don't work. Hope tends to fade in that scenario. Hope fades a little more each day. But here's the good news. There is hope. The researchers then attempted a microbiome rescue, transferring healthy donor microbiomes into fibromyalgia mice to see if they could rescue their pain. And guess what? It did. It did rescue their pain. The mice's pain responses dropped significantly after the microbiome swap, where the fibromyalgia microbiome was swapped for a healthy microbiome. Remember the Von Frey test from just a moment ago? You can see here fibromyalgia mice who then received antibiotic wipeout and were treated with a healthy control microbiome. They exhibited an increase in their pain threshold, the blue line, so a decrease in pain. And this success in animal models laid the groundwork for a small human pilot trial, which was also reported on in this paper. 14 women with fibromyalgia, all of whom had failed standard treatments including multiple medications and lifestyle interventions, underwent a fecal microbiome transplant, an FMT, from healthy human donors. First, their existing microbiomes were wiped out with antibiotics, and then over 10 weeks, they received 5 doses of the healthy donor microbiome. Within just 1 week, signs of pain improved. And by the end of the study, 12 out of 14 women experienced statistically significant reductions in pain intensity, along with notable improvements in mental health, sleep quality, and overall quality of life. And crucially, the patients' microbiomes also adopted the microbiome signatures of their respective donors, along with changes in bile acid and amino acid pathways believed to modulate pain. This supports the idea of a causal microbiome effect, although admittedly, because this study wasn't blinded and lacked a control group, we can't entirely rule out a placebo effect. So no, this wasn't the be-all end-all human study, but it was a fascinating and important first step towards proving that the fecal microbiome transplants, and microbiome modification in general, might one day be powerful tools for treating chronic pain. And while I didn't dive too deep into the immunological and neurobiological nitty-gritty in this video, the researchers did begin to decode mechanisms. For example, they found shifts in certain signaling molecules like bile acids, reduced inflammation, and changes in reactive microglia. The immune cells in the spinal cord and the brain that help control pain signal transmission from the body to the brain. So, in other words, your gut might be talking directly to your brain, and sometimes it's screaming. So, what if poop could treat chronic pain? Well, based on this early but exciting research, it just might. We are in the early days, and bigger, better controlled trials are definitely needed, But for the millions suffering with mysterious and debilitating real conditions, like fibromyalgia, the idea that a microbiome makeover could ease their pain and even lift their mental health is both groundbreaking and full of hope. So I'm sure you're wondering, what can you do today if you're someone who struggles with chronic pain, or what can a loved one do if they struggle? Well, I wouldn't suggest performing an at-home fecal transplant just yet. Because without proper support, it's difficult and probably kind of messy. But if the microbiome does play a key role in mediating pain as these data suggests, then it makes sense to treat it well. Fermented foods like kimchi, sauerkraut, and kefir might provide some benefits, and I have a whole video on that topic if you'd like to learn more. But truthfully, and in my opinion, gut health is just as much about what you don't eat as what you do. So reducing sugar and unhealthy ultra-processed foods filled with ingredients so obscure they might as well be written in another language should be your first stop in treating your microbiome right and potentially helping to manage or prevent nociplastic pain. So the takeaway here, the big picture, the gut-brain axis isn't just some buzz phrase. It's a real, powerful, and still largely untapped frontier of medicine. And sometimes the key to healing what hurts most might just start with a little crap. Now, if you really want to learn more about the microbiome, please check out my recent Microbiome Masterclass video. And don't forget to join the movement, and I'm not talking about peristalsis. Please subscribe for more gut health and metabolic health science. Your support sends a signal to the algorithm that The world wants more health science breakdowns. Now I have a treat for you, an exclusive clip just for you from the first author of this study, Dr. Cai. I asked her, what are the next steps for this line of research? And based on these results, are there safe and actionable steps that people can take, you can take today to potentially help improve their fibromyalgia symptoms? Here's what she had to say.

Thanks, Nick Norwitz, for featuring our work. The immediate next step is to investigate the underlying mechanisms driving the effects of gut microbiota. In other words, how the gut microbiota is actually influencing fibromyalgia. We have shown that fecal microbiota transplantation, or FMT, can both induce and relieve fibromyalgia symptoms. It would be better to identify specific bacterial strains or taxa responsible for both effects. We could eventually help to design more targeted and precise treatment. Now, the mechanisms behind this are not simple. Our current findings point to a few possibilities. These include the changes in immunofunction or reduction in the nerve fibers in the skin and shifts in certain bacterial byproducts, especially metabolites like secondary bile acids, which have also been strongly linked to fibromyalgia symptoms in patients, as you can check in previous work by Dr. Amir Manerbi in 2023. While we don't yet fully understand how these pieces fit together, those observations provide a promising direction for future study. One of our goals is to track what happens biologically after FMT, things like changes in metabolites, immune signals, and chemicals that affect the nerve systems. If we can figure out which of these actually helping with symptom relief, we might be able to employ them in a more controlled way to help patients. In our preclinical work, we showed that Transferring gut microbiota from fibromyalgia patients into mice led to increased pain sensitivity. This supports the idea that the gut microbiota may play a causal role in the disease. But we also recognize that this relationship is likely two-way. Factors like stress, infections, diet, and physical activities can influence both symptoms and the microbiota itself. To answer your, the other question, based on these results, are there safe and actionable steps people can take today to potentially improve their fibromyalgia? I am not a clinician myself, but I worked closely with Dr. Manerbi on this study who brings the clinical perspective. And the answer is yes. Based on these results and what we have seen in past studies, there are a few safe, practical steps people can take right now that might help with fibromyalgia symptoms. Um, they are divided into two groups. First, specific actions that directly improve symptoms, and second, general habits that support a healthy gut. First, diet. Trying a low FODMAP or a low gluten diet can help reduce symptoms in some people and shift the gut microbiome in a good direction. Next, exercise. Doing 30 to 60 minutes of aerobic or mixed activity 3 or more times a week has been linked to increase in butyrate gut metabolites that may help relieve symptoms. And of course, sleep. Getting enough good quality sleep is really important for managing pain and staying well overall. For general gut health, eating more fibers is key. It feeds the helpful gut bacteria that are often low in people with fibromyalgia. Additionally, fermented food like yogurt, kefir, kimchi, or, um, sauerkraut can also help keep your microbiome diverse and healthy. And finally, cutting back on processed foods can support better gut balance and make you feel better overall. So to sum it up, diet, exercise, sleep, fiber, fermented foods, and fewer processed foods. It's not a cure, but some changes like these can make a real difference. Thank you.