
How Microbiomes Affect Fear - ohjeez
https://www.quantamagazine.org/how-microbiomes-affect-fear-20191204/
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sebastianconcpt
_The researchers performed classical behavioral training on mice, some of
which had been given antibiotics to dramatically diminish their microbiomes
and some of which had been raised in isolation so that they had no microbiome
at all. All the mice learned equally well to fear the sound of a tone that was
followed by an electric shock. When the scientists discontinued the shocks,
the ordinary mice gradually learned not to fear the sound. But in the mice
with depleted or nonexistent microbiomes, the fear persisted — they remained
more likely to freeze at the sound of the tone than the untreated mice did._

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moh_maya
So, interesting as the article is, there are two layers of caution one must
exercise in interpreting the results.

#1. The experiments were conducted in mouse models. Mouse models are
remarkably useful, but are NOT human equivalents. It's dangerous to draw a
straight line between human behaviour and behaviour in mice. [1]

#2. Gut microbiome is the latest in the hype train. It may be important, but
again, drawing such a straight (even speculative) line between gut microbiomes
and behaviour is.. a reach [2,3,4].

Basically, I am, in general, very wary of any reports or articles that attempt
to map results in mice to human behaviour and reports of the gut microbiomes
driving autism / Alzheimer's / fear / what have you. This report combines
both, so it gets extra red flags, IMO.

Just my 2 cents.. not saying this isn't possible, but the bar for assuming
this is true is very very high. And the results in the paper are a small first
step in a very very long process required to substantiate this hypothesis.

[1]
[https://www.medicalnewstoday.com/articles/325255.php#1](https://www.medicalnewstoday.com/articles/325255.php#1)

[2]
[https://www.nature.com/articles/s41579-019-0283-5](https://www.nature.com/articles/s41579-019-0283-5)

[3] [https://www.nature.com/news/microbiology-microbiome-
science-...](https://www.nature.com/news/microbiology-microbiome-science-
needs-a-healthy-dose-of-scepticism-1.15730)

[4] [https://www.irishtimes.com/news/science/hyping-the-
microbiom...](https://www.irishtimes.com/news/science/hyping-the-microbiome-
may-have-unpleasant-side-effects-1.3839334?mode=amp)

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rbanffy
It's interesting how much of our personalities relate to our fear responses.
For example,
[https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5793824/](https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5793824/)
notes that the size of the amygdala correlates with economic conservatism.

I now wonder if changes in gut flora can predict political changes.

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crmrc114
I would argue this is not completely new. But still a fascinating look into
how the cities of microorganisms on/in us influence our behavior.

Toxoplasma gondii, an interesting topic if you want to read about how
something in the gut can affect complex behavior in a mammal. Rodents are
actually atracted to the smell of cat pee after being infected with T. Gondii.
[https://www.sciencedaily.com/releases/2011/08/110817175920.h...](https://www.sciencedaily.com/releases/2011/08/110817175920.htm)

For the human perspective;
[https://www.jstor.org/stable/25223400?seq=1](https://www.jstor.org/stable/25223400?seq=1)

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phkahler
Someone suggested to me that some STDs increase sex drive in humans, but I
have not seen any research findings on that. It wouldn't surprise me.

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tsomctl
> The team speculated that the microbiome might produce certain substances in
> abundance, with some molecules making their way into the brain.

I thought this was already well established with sodium butyrate. Eating hi
maize resistant starch is a guaranteed way to give me super vivid, movie like
dreams.

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rolltiide
I get extremely vivid, coherent, controllable dreams after being drunk despite
the accepted science saying drinking/alcohol inhibits dreams of the sleep
state necessary

I’ve met a few other people that said the same thing

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grawprog
I get these if I stop smoking weed. Couldn't smoke during a school trip to the
States years ago, two of the other people I shared a room with also smoked
regularly, all three of us had fucked up vivid dreams for the entire week. I
still remember the one on the first night all these years later. I remember
vividly watching myself disintegrate while a nuke went off nearby while I was
working on something at school.

My dad's also said nicotine patches do the same thing while you're on them.

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loceng
Joe Rogan interview with Matthew Walker - a sleep expert - where they talk
about this:
[https://www.youtube.com/watch?v=pwaWilO_Pig](https://www.youtube.com/watch?v=pwaWilO_Pig)

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idclip
How does one regenerate their micro biome?

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cpncrunch
Prebiotic and probiotic food.

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keyle
There are no scientific evidence that probiotics work or don't work. It's a
50-50 unproven by science. The ones that prove it are sponsored and none
disprove it either. My 50c as a long term IBS patient.

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cpncrunch
As a mostly controlled IBS patient, I find having a good diet works best.
Fruit, veg, whole grains. Avoid sugary soda drinks, caffeine, coffee and too
much alcohol. I think all of those things promote good gut bacteria.
Prebiotics fall into that category.

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jlavine
Out of curiosity, did you get a microbiome test (e.g. from Viome) before and
after removing each one of these elements from your diet, or did you make
conclusions based on how you felt? Of course everyone is different, but I
think published research supports your suggestion that sugar and alcohol are
"bad" and fruits, vegetables, and resistant starch are "good", but disagrees
on coffee. Here's a recent study showing association between high coffee
intake and "good" gut microbiome [1]. I put good and bad in scare quotes
because it seems the science around this is still pretty weak, mostly based on
associations rather than clear and verified mechanisms. [1]
[https://gi.org/media/press-info-scientific-
meeting/featured-...](https://gi.org/media/press-info-scientific-
meeting/featured-science/p1916-caffeine-consumption-and-the-colonic-mucosa-
associated-gut-microbiota/)

~~~
cpncrunch
Sorry for the confusion. When I mentioned coffee I was referring to IBS
symptoms, not microbiome. Caffeine increases digestive secretions and causes
colonic motor activity. Even decaf coffee increases secretions. For a review,
see:

[https://www.tandfonline.com/doi/abs/10.1080/0036552997500255...](https://www.tandfonline.com/doi/abs/10.1080/003655299750025525)

If coffee is causing IBS symptoms (diarrhea), I would imagine that isn't good
for your microbiome.

I haven't had any microbiome tests, and it's very difficult to robustly test
for the effects of individual foods without doing a placebo controlled trial.
However, after removing fizzy HFCS soda drinks, I seem to not have any
symptoms that I would associate with an abnormal microbiome in the past year
(smelly farts, followed by urgent need to poop, followed by large amount of
soft poop after eating, during a period of long-term zero stress). I've made a
number of other changes to my diet, such as not drinking tap water, but I
suspect HFCS was the main culprit, as the scientific evidence strongly backs
that up.

Stress is another main cause of IBS, due to its effects on gut motility.

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yellow_lead
> _The researchers performed classical behavioral training on mice, some of
> which had been given antibiotics to dramatically diminish their microbiomes
> and some of which had been raised in isolation so that they had no
> microbiome at all._

As someone who is currently on antibiotics, I wonder what effect different
antibiotics have on human brains. It would probably not be too hard to setup a
similar study, antibiotics are currently thought to be mostly harmless AFAIK.

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johnsimer
FWIW the gut is often referred to as the "second brain", and the microbiome
wrecks havoc on the gut

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taneq
I apologise in advance for being super-pedantic here but it's "wreaks"
(meaning "spreads/imposes") rather than "wrecks" (meaning "destroys").

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krishsai
Nice read!

