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I believe this research is totally true-- I had a lot of memories come back after

1. I stopped drinking heavily and using other drugs, i.e. marijuana

2. managed my diet to avoid heartburn without medication

3. schedule my meals so it was easier to sleep at night (always eat something for breakfast when I wake up)

I did not need any "poo infusion" or anything.

I had a gal bladder removal that didn't fix the problems the doctors thought it would and got a lot smarter about the kinds and variety of food I eat.

I believe alcohol in particular was really screwing up my gut biome and entire digestive system.

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weird. gal bladder removal made me a lot smarter too. no, really. cuz it didn't fix my problems either. well, it did but in an unexpected way. because it forced me to ask myself the real questions. so i started fixing my life, bit by bit. trial and error.

theorem of indirection, i guess.

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> 1. I stopped drinking heavily and using other drugs, i.e. marijuana

Heavy alcohol use and marijuana are both known to impact memory and recall directly.

Discontinuing both of those explains changes in memory. Attributing this to microbiome changes does not follow.

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This paper actually surveys research on humans and not mice.

The association between gut microbiota and cognitive decline: A systematic review of the literature

https://www.sciencedirect.com/science/article/pii/S027153172...

It shows ”Gut microbiota modulation improves cognition in adults with early impairment. Diet, probiotics, and fecal microbiota transplantation share mechanistic pathways and that evidence clarifies how microbiota-targeted strategies support cognitive health.”

The action could be explained due to an anti inflammatory action by the gut biome.

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Yes, there are some interesting potential mild modulations that can occur with microbiome change.

That paper commits one of the major sins of many microbiome papers which is to attribute all benefits of diet change to the microbiome. Like the parent commenter it gets drawn to the idea that all changes in the body can be traced back to the microbiome and assumes that it explains everything, but that’s obviously not true.

However, when someone is taking two powerful substances with direct brain action and known modulators effects on memory, blaming anything else in the body is bad logic.

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>Heavy alcohol use and marijuana are both known to impact memory and recall directly.

And who said they don't do this (long term) exactly through their affecting the gut microbiome?

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I think the appropriate response here is some combination of Russell's Teapot and Occam's Razor: they might, but some kind of hard evidence is necessary before humouring that theory, particularly since there's a vastly simpler explanation on hand.
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Both alcohol and marijuana have direct actions on the brain. That’s why people consume them.

They do not exert their primary effects via microbiome modulation. This is obvious because the effects occur nearly immediately upon consumption, whereas microbiome change from what you consume is a gradual process.

The question I have is: Why has microbiome become the explanation for everything? What would lead you to believe that microbiome would be the explanation for this, when the direct action upon the brain is so much more direct and obvious? Microbiome is an interesting area of research but how did we get to this point where some are ignoring the obvious and trying to construct alternative microbiome based explanations for things like alcohol and marijuana impairing memory?

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>Both alcohol and marijuana have direct actions on the brain. That’s why people consume them.

Which is orthogonal as to whether those direct actions also affect long term memory.

>They do not exert their primary effects via microbiome modulation.

Who said anything about primary effects?

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Or by affecting the kidneys, or by affecting the enteric nervous system, or through some other pathway for which we have no substantial evidence of influencing memory (yet). It just seems like a baseless prioritization of a hypothesis. For some reason, people are specifically fascinated by the gut–brain axis.
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>For some reason, people are specifically fascinated by the gut–brain axis.

Might the reason be that we're constantly finding new important ways it affects things, or that we see major changes to seemingly orthogonal issues from targetting the gut microbiome directly?

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It has been well recognized that alcohol significantly disrupts the bacteria in your gut.
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Also, getting better sleep (by fixing heartburn and meals) will mean you're more rested, and improve functioning during the day.
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It could easily be both.
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Fascinating to hear. I am trying to cut alcohol - still not entirely successful.

But I've been able to cut for months at a time. Whenever the cut happens, I feel my brain sort of "return" roughly a week or two in.

I'm not sure how to explain it other than something like fog clearing. Obviously makes some intuitive sense when you read it.

However, as someone that has consumed alcohol somewhat regularly (sometimes more, sometimes less) since college, it's bizarre to think about that consumption in retrospect. In effect, years and years of "fog" - it makes me wonder how different or similar life would have been without that fog.

Can't change the past now, but a data point and strong signal for the future.

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I feel that same way you described with the "fog" clearing. I don't know exactly what it is, but I'm imagining it being the fact I _finally_ get some good, restful sleep (with it taking about 2 weeks give or take for that clear headed feeling to regenerate).
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The really crazy thing that happened to me when I changed diet to a more gut-biome friendly* is that (like I craved sweets before) I started craving vegetables and oatmeal. Like there was a regime change in my gut and the new guys pushed the buttons to get more of their food.

(less/no simple sugars, much more vegetables and starches/fibers, regularly eating 4 corn/20 plant oatmeal few times a week)

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> 4 corn/20 plant oatmeal

What does this mean?

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It's my own idea for a super oatmeal. Working on the idea that it's not just about having fiber in your diet, but more so about variated fiber. Each kind of fiber is preferred by a different type of gut bacteria (I'm just repeating after some hippy that most likely made that up). And the best gut biome is the most variated one. Usually pathologies stem from monocultures. Look at the most of the society. Bread, cookies, pretzels, even pizza etc. - it's all made of wheat. Sometimes you'll get oat cookies. But other grains show up in people's diets very rarely.

Here's the recipe. I'm using norwegian 5-grain oatmeal that has oats, wheat, barley, rye and spelt:

Recipe: Use two parts oatmeal (either 4-korn or 5-korn). Add one part nut mix and one part seed mix. So for 50 g of oats, add 25 g of nuts and 25 g of seeds.

Seeds: 30% flaxseed 30% chia 20% pumpkin seeds 20% sesame

Nuts: 4 parts walnuts 2 parts pecans 1 part Brazil nuts

P.S.: since most of these ingredients are pretty cheap (oatmeal used to be poor mans food), you can upgrade to Eco versions of these and get much better taste, without going that much up in price. Especially nuts.

Also, I have the nutmix and seed mix pre blended in 2 liter jars, so that I only have to mix them once a month or two.

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What did you do for heartburn? Just looking for ideas. I noticed reducing gluten helped me personally a lot
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I stopped taking esomeprazole after being on it for 4 years, and frequently had to supplement with famotidine and tums anyway.

I had an infection and was prescribed antibiotics, and needed to pause the esomeprazole. I asked gemini about it and it suggested I take two probiotics while on the antibiotics, Saccharomyces boulardii and Lactobacillus rhamnosus GG. I noticed after a few days that I wasn't getting heartburn, and started putting the pieces together.

After the antibiotics ended, with still no heartburn, it recommend I add rhamnosus gg to the mix. So now I take all three daily and rarely get heartburn. It's been quiet a shock

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There is a weak association with use of PPIs and memory loss. I myself noticed a difference once I stopped taking omeprazole regularly.
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Most doctors will say avoid long term use of PPIs for a variety of reasons. Famotidine is much easier on the body, albeit less effective than PPIs.
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thank you going to try this. I noticed my heartburn got a lot worse after having to take a few courses of antibiotics.
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Some good notes on heartburn, a fiber regime, some combination of wheat dextrin, psyllium husk, inulin. All 3 are different and serve a somewhat different function.

Foods to eat, oatmeal, lentils.

Ginger tea, activated charcoal tabs.

Most all of that works very well to support gut bacteria so throwing some probiotics in as well can help. The gummy kind available in generic or Digestive Advantage work well!

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Im not saying to live this way, but a super restrictive test diet may open your eyes to some thing and then you can add back.

I even once read that someone noticed an issue they tried to clear up for years with doctors went away on day 3 of a water fast. No, he wasn't going to fast forever. But he was shocked the first relief he ever had was that day. From there he solved his problem once his eyes were opened a bit.

I'd personally try all ground beef for a week or two. It won't kill you. Is it ideal? Probably not. But you will not have any problems from that short trial. Then add things slowly until you have a whole good diet you like.

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It may not work for you but I had years of chronic heartburn. While sick with covid in 2020, I stopped consuming coffee and alcohol. It took a few months and for the long covid symptoms to subside, and then no more heartburn. At all. I felt really dumb that I never connected it to coffee before. I didn’t experience direct symptoms from coffee and I didn’t consume an excess amount. But it definitely was the cause.
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The kind of coffee you drink can make a huge difference as well. Filter coffee is typically larger in volume so there’s more acidic liquids going in to trigger your heartburn. Compared to espresso which is usually a smaller volume. It can be a huge difference in heartburn between coffee types.
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I can confirm that eliminating coffee can make a big difference.
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I'm a couple weeks into giving up coffee because of heartburn, and yeah, this tracks... unfortunately. I've replaced heartburn with heartache (having given up a beverage I've enjoyed daily for over 20 years).
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What kind of coffee were you drinking? I replaced filter coffee with espresso and my heartburn went away.
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Good luck, my friend. I’m right there with you. It’s not the physical effects but the rituals and the social connections that I miss. I felt the same with coffee as I did with smoking, which I quit about 20 years ago. It’s remarkable how much these simple vice shape our daily lives.
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Yup. Discovered me and my dad have ADHD at pretty much the same time. In our case (very stimulant sensitive) we had to quit coffee to use ADHD meds. While I eventually switched to Inka (a roasted grain coffee substitute) when I saw how my heart results get better without coffee, he still struggles. He recently quit meds for some time due to unwanted symptoms and told me how he was away with some friends and deeply relished being able to normally drink coffee again.
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not the commenter but I bake my own soda bread and found that i was getting heartburn from the salt that was in the recipe. once i eliminated that i could eat as much as i wanted. I also cannot eat salt preserved potato chips on consecutive days.
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I kind of wonder if sometimes acid reflux happens more than we realize, but we just notice it when spicy food comes up.
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Pretty sure this is correct. You only notice it when it comes right out of the top. Other days it may be 25%, 50%, or 75% of the way up. And that's still bad for your oesophagus over the long term. My dad got cancer right at the bottom and one potential cause was chronic acid reflux (GERD leading to Barrett's eosophagus).
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It might not be gluten (protein) that is affecting you, but the fructans (carbohydrates) that are found in wheat, rye, and barely which are high in FODMAPs.

Look into low-FODMAP diets if you haven't already.

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My "chronic" acid reflux disappeared at USMC boot camp so...exercise, no snacking, no alcohol, and rigid sleep schedule?
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There are many resources online on which foods trigger gerd and reflux. Also, try the whole30 anti inflammation diet, and don't eat at least 2, preferably 4h before bed.
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Your hypothesis here though is full of complicating factors.

For example

>I stopped drinking heavily and using other drugs, i.e. marijuana

Like the primary change you made was to cut out using a whole bunch of drugs with known, significant neurological effects.

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I think the "and" is for "stopped (both) A and B"
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Yes, that's what they're pointing out. Changing multiple variables at once means you can't attribute changes to any one of those variables in particular.
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So, you stopped being an alcoholic and pothead, and your memory improved?

Wow, it must be those gut microbes!

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What unnecessary snark. Is a little civility too much to ask for?
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Ridiculous claims deserve to be ridiculed.
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In my opinion, gut microbiome stuff is massively overhyped.

Here's a study that tried fecal transplants to treat mental illness (and found no effect): https://pubmed.ncbi.nlm.nih.gov/41785480/

The pattern with this stuff is that, when a blinded study is carried out, there's usually no effect.

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Here's a meta analysis of 12 studies showing that FMT has a significant effect in reducing depression:

https://pmc.ncbi.nlm.nih.gov/articles/PMC12536323/

It also found the effect was greater in people with IBS.

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This meta-analysis isn’t very convincing. Most of the studies included were primarily about other measures like IBS, COVID-related GI symptoms, or Fibromyalgia. Improving GI problems would be expected to improve mood.

The positive result is heavily driven by an outlier study on Fibromyalgia that has results that look a little too suspicious relative to the other studies.

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I wonder how that study would fare against a double blind where some people get FMT and others do not, but they are both given the same attention and care otherwise over the course of the study?
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I think mainstream is mostly looking at the microbiome stuff wrong. Your microbiome is the downstream proxy of good lifestyle habits, not generally something to directly manage. Good diet, exercise, reducing stress, and sleeping well will improve digestion and all the downstream variables like microbiome, physical health, and mental health.

This is basic ecology, the bacterial population dynamics in your colon are a direct result of substrate availability. If it’s primarily fiber, polyphenols, and other indigestible plant compounds reaching the colon you’ll likely have a healthy microbiome. If instead you malabsorb food from poor lifestyle factors and have macronutrients reaching the colon they’ll probably fuel blooms of pathogens. I think microbiome researchers need to talk with ecologists more to help advance the field out of the myopia it’s in.

FMT does appear useful for special cases of infection like c-diff, but I think that’s led people to believe it’s a generally health promoting practice, when the research simply does not show it.

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I like this measured take, but I think we can also expect it to be a virtuous cycle.

Sure, you have to put in a lot of effort to get the system starting, but eventually the feedback loop pays dividends that outweigh the principal.

Everything else about the human body seems to be this way, adaptation or maladaptation.

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It certainly anecdotal, but feels like you can positively effect your gut microbiome for example by riding a horse. Ive read research about how other mammals can share their microbiomes with humans, if its not the horses biome then what is it that so satisfingly calming post ride. Would love to be enlightened. Ride a horse if you need to destress, amazing creatures.
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It certainly anecdotal, but feels like you can positively effect your gut microbiome for example by riding a bicycle. If its not the bike's biome then what is it that so satisfingly calming post ride. Would love to be enlightened. Ride a bike if you need to destress, amazing machines.
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https://www.frontiersin.org/journals/cellular-and-infection-... https://www.cell.com/iscience/fulltext/S2589-0042(25)02209-6 https://www.sciencedirect.com/science/article/pii/S235277142...

im talking about impacting your microbiome through another animal, not the short term effects from aerobic exercise or BDNF and what that feels like. this experience didnt hit quite like other typical metabolic functions.

great to hear you like BDNF. we all could use more of that.

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These articles talk about subtle changes to one's microbiome by cohabiting with animals and trading microbes with them. That's a process that takes place over months if not years.

Meanwhile, you suggest that such microbial influence must be reason you feel calm right after riding your horse.

I don't think I need to further explain why it's a ridiculous claim.

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i guess in that case, washing woth soap everyday is probably a negative factor?
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Washing with soap everyday unless you are very dirty is indeed negative and can dry your skin. Especially as most of what is called soap now is not soap but a very complex collection of synthetic organic chemicals.

Exactly how negative it is though is difficult to determine and probably varies from person to person.

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Replying to slibhb, while the research involving mental illness is not conclusive, fecal transplants are a known and accepted treatment for persistent C. diff (Clostridioides difficile) infection. Just for the record.
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This seems like it makes way, way more sense
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>The pattern with this stuff is that, when a blinded study is carried out, there's usually no effect.

It must be the case that these microbes need the subject to be aware of their presence! Maybe the microbes have consciousness, and for the treatment to work, the microbes' consciousness has to entangle (via quantum mechanisms) with the subject's consciousness? Blind studies prevent this quantum entanglement to form, that's why the treatment stops working. We definitely need more research in this direction!

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They found a 15 point MADRS change in the placebo group, that's huge, it's only a 60 point scale, and more than the average SSRI produces. Either the procedure itself is doing something or something isn't right with the study.

Also one issue with all of these studies is they only look at averages and don't do subgroup analysis. It may be that a few patients have an underlying condition causing depression that is highly responsive to these interventions, while it has no effect on the others.

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You are probably right on the specifics, but serotonin is produced/located in the gut, and its an incredibly important neurotransmitter.

One day people will figure out how to use these correctly.

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> but serotonin is produced/located in the gut, and its an incredibly important neurotransmitter.

Serotonin in the gut doesn’t go to your brain. It serves a different function in the gut.

The brain synthesizes serotonin inside of the brain. It doesn’t come from your gut.

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Thanks for following up with a correction. This is a myth that simply refuses to die. I cannot even count the number of times I’ve heard people repeating it.
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There are a lot of HN users that think they are better at science because they know about p-hacking and the limitations of animal models.
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There was a South Park episode about this years ago where everyone was trying to get it from Tom Brady.
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The Spice Melange
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I would recommend the site https://gutbrainaxistherapeutics.com for learning more about Microbiota Transplant Therapy (MTT) and its opportunities, especially for Autism and Pitt-Hopkins Syndrome.
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Fecal transplants...people will do anything to avoid eating a balanced, largely/wholly plant-based diet with a wide variety of fruits and vegetables.
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I think the idea is that the biome is built up over time and you can't always just eat your way to certain bacteria growing in your gut.

I think the fecal transplants help to essentially seed your gut with healthy bacteria, which makes adapting to the proper diet easier when your body isn't constantly fighting you.

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I’ll dig in more but my first question when I see this: who are the donors exactly? Like who decides what the ideal gut microbiome is and that John Doe is the guy to provide his fecal matter to the masses?
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More importantly: are there places that will pay me to make regular donations?
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You either need a lab to test donor samples first, or when this was more of a craze, a popular source of 'donations' for the DIY crowd was young children.

If you're interested in digging into the people that were doing this, they had a website dedicated to everyone telling their stories of how they went about their own individual journeys.

The website was called thepowerofpoop.com and looks like it's gone now, but is available on the wayback machine including individual articles and images.

I would go back to at least 2022 .. I think they possibly got in legal trouble at some point and started taking things down.

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I would not recommend that site as a good resource.

Microbiome transplant therapy is a domain full of grifters right now who will push it to vulnerable populations desperate for hope, like parents of autistic children. The real research results are much less promising for difficult conditions.

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There is zero evidence that poop transplants have any effect on autism, let's be clear here.
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Not true; their clinical trials[1] finds Improvements in GI symptoms, ASD symptoms, and the microbiome all persisted for at least 8 weeks after treatment ended, suggesting a long-term impact[2]

More recently, a study finds The modulation of the gut microbiota using MTT in ASD has shown beneficial and long-term effects on GI symptoms and core symptoms of autism[3]

[1] https://gutbrainaxistherapeutics.com/pipeline/#clinical-tria...

[2] https://link.springer.com/article/10.1186/s40168-016-0225-7

[3] https://www.tandfonline.com/doi/abs/10.1080/19490976.2025.24...

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"Reversing memory loss in mice via gut-brain communication"

And nobody is bothered by the story. And it gets less clicks. People get cranky when they have been suckered.

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"butt juice infusion" xD
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Not only are there tons of papers, there are off-label treatments (some that have improved more than 80% of the folks I'm about to mention), and this isn't just about age related decline, but cognitive impairment in general. Long COVID, ME/CFS, TBIs, and other conditions are widely considered to have a similar origin. If you are interested in this stuff, I encourage you to look up all the scientific papers on this. It is fascinating stuff.
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Most of the serotonin we produce comes from our gut.
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Serotonin produced in the gut doesn’t get into your brain.

This factoid is repeated everywhere but it’s misleading without knowing that gut serotonin is a different pool than brain serotonin and they have different functions.

The brain synthesizes its serotonin locally within the brain.

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Serotonin from the gut affects vagal neurons. They carry that signal directly to the brain. That has a significant effect on up and down regulation of mood and arousal.
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Okay that’s like my company that uses Salesforce that sends an invoice to another company that also uses Salesforce.

The fact that we both use Salesforce does not matter. It’s internal and doesn’t mean anything outside the company. Both the brain and gut re-used the molecule for their own internal signaling. Evolutionarily it was cheaper to use an existing molecule.

To the brain, the invoice is just “I’m full” or “I’m hangry.” It doesn’t care how much serotonin the gut had to produce internally to issue that “invoice.” The brain will produce its own serotonin from the signal of satiety but it won’t give you any more than you can from just feeling full.

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It is a powerful neuron hormone. The mechanisms are different. It is still important to recognize the rather dramatic influence this has on the brain. That was what this article was about. This pathway can easily lead to depression and significant broad down regulation in the brain. Serotonin inside of the brain works very specifically. The vagus nerve signal has a very broad impact and should not be hand waved. If your vasovagal system has dysregulation it can lead to all sorts of specific brain internal negative outcomes systemically. I think your model of how this works is not very accurate regarding how broadly connected the vagal signaling pathway is and how that impacts how your brain functions.
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The blood brain barrier is a deny by default firewall. If there is no transporter configured for a particular molecule, it doesn't get through. There is no transporter for serotonin
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Your nervous system extends over your entire body, the brain doesn't live in a firewalled jar.
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To extend the metaphor, the brain may have a robust firewall, but it also transacts with millions of clients over a separate (electric rather than chemical) network.
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See: vagal neurons and vagus nerve. Serotonin from gut directly impacts those. Your brain still directly interprets that signal from the vagus nerve and uses that to up and down regulate mood and arousal. Impact is still significant
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This seems to be a recent anti-science meme to dismiss studies that use mouse models. I'm sure there is an interesting line of discussion about the strengths and limits of those models, but that's probably a complex, nuanced thread to pull, not something you blow off with a hand-waving internet comment.
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To some degree the other posts are just pointing out the misleading "assumed protagonist" of the title (which doesn't mention mice) but I was surprised to see that the majority of posts boiled down to "eek! mice!"
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I wish I could filter the word mice or mouse out of hn comments because as you say every single one are low effort gotcha's that I will never get my time back from.

It is like these armchair scientists don't understand that the actual scientists know the limits of the model system better than they do.

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It's not anti-science, it's anti-science-journalism-hype.

Science depends on accurately reporting facts, being clear about the limits of your findings, and seeking explanations that survive scrutiny. Science journalism has other priorities that are often in conflict with those of science.

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I bet it started with people trying to 1-up other commenters via the usual “achtually…” and then proceeding with the “in mice” notice.
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