Gut-Brain-Penis Axis
A bizarre new perspective on erectile dysfunction.
“A hard man is good to find” —Mae West
Spare a thought for the grad student whose job is to monitor erections in rats. And yet, that dedication may pay off with better, if weirder, treatments. A new scientific review from China has looked into fecal transplants to improve erections and finds that they show potential.
China has a problem, with some studies showing that 40% of Chinese men have erectile dysfunction (ED), which only gets worse with age. America is close behind, with some 20-40% of men over 40 afflicted by ED.
ED can be caused by both psychological and physical problems. Some of those physical problems include diabetes, hypertension, and obesity. According to the Lancet, over half of the Chinese population is overweight or obese, which may provide some hints for solving their ED problem.
Dysbiosis
To these issues, you can now add gut dysbiosis, which is a term used to describe a gut microbiome that is out of balance. People with ED have more disease-causing pathogens like Actinomyces dominating, and certain healthy species of Coprococcus and Ruminococcus diminishing.
Perhaps not shockingly, obesity is also related to dysbiosis. In rat experiments, it is easy to induce dysbiosis by feeding a high-fat diet, which causes ED to increase along with overweight.
The idea that diet could cause ED is intriguing, which led some researchers to take an extra step. In order to see if the ED problem is related to gut microbes, they transferred the poop of the ED rats to normal rats. This is called a fecal transplant, and it would be more disgusting if rodents didn’t regularly eat each other’s feces anyway.
Amazingly, the microbes from ED rats transferred their ED to normal rats. Moreover, transferring healthy microbes to rats with ED helped them to lose weight and gain back erectile function. Microbiology is full of loose correlations, but fecal transplants demonstrate causality. There may be other factors involved, but at least some of the ED story looks to be microbial.
How does it work?
But how can tiny microbes affect sexuality and arousal?
The answer lies in how the microbiome works. As soon as animals popped on to the planetary scene, they had microbes, simply because the planet is awash in them. There is no escape. And they would devour us all if we didn’t recruit some friendly microbes to work on our side in return for a warm wet home with regular meals.
This is the primary appeal of a microbiome: it fights off pathogens before our immune system even knows they’ve landed. As a bonus, microbes also create nutritious fatty acids from substances we can’t otherwise digest, like fiber.
But animals have an immune system that is designed to attack microbes, so how does that work? It’s a tricky balance, but early in our lives our immune system goes into learning mode. It assumes that mother’s milk contains good microbes and therefore gives them a life-long pass. When we are weaned and have an established microbiome, our immune system stiffens into a microbe killer that makes exceptions for these “old friends”.
This locks both the immune system and the microbiome into an amazing interkingdom alliance. Between microbes killing pathogens and the immune system repelling strangers, it is very difficult to change your microbiome. Any microbe looking to make our gut their home faces a daunting gauntlet of defenses.
Changing your diet affects your microbes but mostly rearranges their ratios. That is certainly good enough to improve a dysbiotic gut, but it may not cure it. And thus, the recent interest in fecal transplants, which completely reboot your system with a healthier microbiome from a donor super-pooper. The effects can last for years. Biologists call it repoopulation.
Fecal transplants can stop inflammation
The FDA approved use for fecal transplants is to deal with a bad side-effect of antibiotics. As well as diet, antibiotics can change your microbiome, but usually not for the better.
Most antibiotics are indiscriminate killers, knocking out all but the most resilient microbes. Among those is the microbe known as C. diff, that can encapsulate itself into tough spores to survive almost any antibiotic. It triggers a nasty, deadly inflammatory response. C. diff kills 30,000 people a year, almost all of them from hospital-administered antibiotics.
Since these infections are caused by antibiotics, they are hard to fix with antibiotics. And thus, in the 1950s, a human fecal transplant was attempted, and happily, it worked to clear the infection. To this day fecal transplants remain a powerful and singular cure for C. diff. It may seem icky, but to a person suffering from this terrible sickness, it is a godsend.
Getting a new microbiome
For diseases involving the microbiome, fecal transplants hold a lot of promise. And that extends to ED as well. Both obesity and diabetes, sometimes lumped together as “diabesity”, can lead to dysbiosis. Low level inflammation caused by the dysbiosis can lead to cellular damage in the cavernosum of the penis, the structure that fills with blood to produce an erection. This, along with other symptoms of dysbiosis like depression (via the gut-brain axis), lowers the libido significantly.
Short of fecal transplants to replace a dysbiotic gut with a healthy gut, we have some personal leverage. We can ameliorate gut problems with diets high in fiber-containing veggies like beans and onions. We can lower the consumption of sugar that favors pathogens. We can exercise more, which has an unexpected benefit to our microbiome, and may thus help ED.
This research shows one way to make a real impact on our sexual health. It can’t be much fun to do these rat studies — and rat microbes aren’t exactly the same as human microbes — but the knowledge gained can help to make us healthier and sexier. The next step is clinical studies, and I’ll keep you posted when we know more.
References
Chen, Junyi, Chenfeng Bu, Xia Li, Lei Wu, and Xingxiang He. “Therapeutic Potential of Fecal Microbiota Transplantation for Male Sexual Dysfunction: Evidence and Clinical Perspectives.” Microbiota Medicine Research n/a, no. n/a (n.d.). https://doi.org/10.1002/mmr3.70003.
Xu, Zhunan, Shangren Wang, Chunxiang Liu, et al. “The Role of Gut Microbiota in Male Erectile Dysfunction of Rats.” The World Journal of Men’s Health 43, no. 1 (2025): 213–27. https://doi.org/10.5534/wjmh.230337.
Thank you for this engaging and thought-provoking piece! I love how you took a concept that might initially sound provocative and grounded it in a broader physiological framework. Framing the gut, brain, and sexual function as interconnected systems reflects an important shift in medicine from organ-specific thinking toward network biology and bidirectional signaling. What stood out to me most was the implicit recognition that pathways like inflammation, vascular function, hormonal signaling, and the microbiome don’t operate in isolation. The gut–brain axis is already well established, and extending that conversation to include sexual health highlights how systemic processes, such as metabolic health, endothelial function, and neurochemical signaling, can converge in ways that are clinically meaningful. One aspect that might further strengthen the piece would be to more clearly distinguish between well-established mechanisms and areas that are still more hypothesis-generating, particularly around the microbiome’s role in sexual function. This might help readers and patients better calibrate where the science is most robust versus still emerging.
Such a compelling and memorable read. Thank you for pushing the conversation beyond traditional silos and encouraging a more integrated view of physiology!
Equal parts fascinating and disturbing… but so well written that I actually understood it — and was even able to explain it to my 23-year-old son, who has not stopped wanting to puke. 🤢😂