Everyone's "poo-pooing" the article because the title doesn't mention mice, but, FWIW, stories of gut biota affecting humans behavior have been documented for a while.

Memory gain is noteworthy, which is the article's "wow" factor, but everyone's just knee-jerk smirking so ... here's a few random articles to gross you out about the wild world of trading microbiota and, for better or worse, changing your personality:

  * "My butt made me crave candy."[1]
  * "Gee, I'm not bipolar anymore thanks to my husband's butt juice infusion."[2]

Crazy, right?

   [1] https://www.psychologytoday.com/us/blog/the-behavioral-microbiome/202404/hacking-an-individuals-personality-through-their-gut-contents

   [2] https://www.abc.net.au/news/2025-07-28/faecal-microbiota-transplant-credited-with-curing-bipolar/105541522

Yeah, it's a mouse study, but there are tons of human studies backing the whole gut-brain connection. There are even a bunch of books on it [1][2].

What's really cool is that the paper used low-dose capsaicin (just 5 μg/kg injected), and it completely restored hippocampal FOS activity and memory in older mice. Basically, that's the same stuff you get in cayenne pepper supplements - pretty easy to get your hands on.

[1] https://www.goodreads.com/book/show/28837738-the-mind-gut-co...

[2] https://www.goodreads.com/book/show/35210457-the-psychobioti...

IMO people should eat more fiber. A lot more fiber. It cleans the gut, the liver, absorbs cholesterol, slows insulin response and makes you feel full longer. The microbes in our guts need it to function.

Rather than jumping from one fad diet to another, just eat what you like and be sure to get a lot of fiber each day.

For those who may be interested in learning more about the gut and how it affects your body and brain, this is a great, accessible, read

https://www.amazon.com/Gut-inside-story-bodys-under-rated/dp...

Also, while we're on the topic, if you ever find your self at the other end of the world in Tasmania, I highly recommend a visit to the MONA museum, which houses the Poo Machine.

https://www.abc.net.au/news/2017-11-07/mona-poo-machine-join...

Say the line HN!

The book

"Why Isn't My Brain Working?"

by Datis Kharrazian

published in 2014 talked about this over a decade ago.

i like how this research (and others related) kind of supports the idea that free will might be lacking. I still keep a pinch of skepticism about this idea, understanding that it's just a concept. But personally i like it, because it even fells a bit relieving... not to say that it helps you abandon responsibility, but it makes your stance on life easier, and pushes you not to blame yourself too much for your weaknesses.

> They showed that colonizing the guts of young mice with this bacterial species inhibited their performance on the object recognition and maze escape tasks, and that this deficit correlated with a reduction of activity in the hippocampus.

Great info. This is one of those things that it is much faster for an individual to take into their own hands to prove out, rather than waiting for the system to provide us with an answer. Too many decision makers who are unlikely to all be aligned with our own individual interests.

I got into bicycle touring a few years ago, and it’s an ultra-endurance activity which means burning 3- 4 times as many calories as I would on a sedentary day. My training rides were all local weekend overnighters in preparation for the big 1000 mile challenge ride, and they were no big deal.

On the big ride, about 3 days in I started experiencing bouts of intestinal distress which would put me into some of the blackest moods I can recall experiencing as an adult. My whole thought process broke down and I became ruthlessly nihilistic about everything. I was ready to tell my partner to go fuck himself, chuck my bike off a bridge and take an uber to the nearest airport.

But then when the intestinal distress subsided I came back to my senses and I was like “WTH was that all about?” It happened several times, to varying degrees of intensity over the 10 day tour. My eating strategy improved and I bought some cannabis which helped my manage the issue and I was able to complete the tour.

That was a few years ago and I’ve never experienced the black mood again. It has prompted me to believe that the mind-gut connection is much stronger than we might have been giving it credit for, and if you suffer from mood or cognition issues, big or small, you may want to investigate whether your guts and gut flora might be playing an influential role.

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... in mice. So if any of this held in humans, I think you'd see reversal of old-age memory problems in people treated with antibiotics that kill Parabacteroides goldsteinii.

As far as I know, no such effect has been observed.

And this article claims inflamation from that strain, the NIH claims otherwise: "Parabacteroides goldsteinii is a next-generation probiotic gut bacterium with significant anti-inflammatory and metabolic benefits, often reduced in obese or diseased states. "

Mice mice mice. Tell me when you test on humans

I smell bad data. This sounds too good to be true and most studies of this kind have turned out to be false a few years down the line.

Edit: one of many examples: https://www.science.org/content/article/journal-retracts-inf...