upvote
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.

reply
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.

reply
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?
reply
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.

reply
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.

reply
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.
reply
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.
reply
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.

reply
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.

reply
i guess in that case, washing woth soap everyday is probably a negative factor?
reply
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.

reply
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.
reply
This seems like it makes way, way more sense
reply
>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!

reply
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.

reply
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.

reply
> 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.

reply
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.
reply