How Microbiomes Affect Fear | Hacker News Reader

How Microbiomes Affect Fear

quantamagazine.org

146 pointsohjeez40 comments

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.

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

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

[3] https://www.nature.com/news/microbiology-microbiome-science-...

[4] https://www.irishtimes.com/news/science/hyping-the-microbiom...

It's interesting how much of our personalities relate to our fear responses. For example, 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.

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...

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

The "for the human perspective" link is to

Parasites as causative agents of human affective disorders? The impact of anti-psychotic, mood-stabilizer and anti-parasite medication on Toxoplasma gondii's ability to alter host behaviour (Proceedings Biological Sciences, 2006)

Download links: http://gen.lib.rus.ec/scimag/?q=Parasites%20as%20Causative%2...

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.

> 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.

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

Inhibits its patterned formation and continuation; doesn’t inhibit it from forming at all.

I'd be open to that but a lot of literature on the internet basically says something to the effect of it prevents dreaming

I’m not sure what literature on the Internet says, but its not what I learned in my sleep medicine rotation. shrug

Watch this Joe Rogan interview with Matthew Walker - a sleep expert - for answer that doesn't counter science on alcohol: https://www.youtube.com/watch?v=pwaWilO_Pig

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.

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

Based only on what you wrote, I see two possible factors: taking a break from weed, or being on a school trip to the U.S.

I get weird, vivid dreams after drinking some wines. After a lot of experimentation, I narrowed it down to Lodi Zinfandels, which raises an interesting puzzle: Is it something in the soil, or are the local winemakers in some sort of competition to hotrod their wines?

I’ve always heard that it inhibits REM (dream) sleep, but as it wears off, your body tries to make up for the lost dream sleep and you get the flood of crazy dreams right before you wake up.

Interesting I hadn’t heard the follow on part

What do you mean by movie like? I periodically have dreams in which I do not show up with characters, sometimes voice over narrative, and plots - is this what you mean. An ex-girlfriend of mine called them epic dreams.

How does one regenerate their micro biome?

Fecal matter transplant.

Prebiotic and probiotic food.

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.

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.

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-...

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...

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.

Damn, are caffeine and coffee associated with bad gut health? Is that anecdotal, or do you know of any research?

Not gut health, but IBS (see my other comment here).

Anecdotally, post antibiotics this winter I had some yogurt and my gut started acting more normal within the day. Not data but definitely seemed to help me.

Alternatively maybe I was already moving past the hump and would have felt better regardless but after antibiotics I’m not sure how I’d get back to a good baseline easier than yogurt or sauerkraut.

It's hard to know without doing a placebo controlled trial. I eat Activia every day, but even I'm not sure it's having any effect and I don't trust Danone's own research. Overall, research seems to be mixed:

https://badgut.org/information-centre/a-z-digestive-topics/p...

Still, I think it's worth using probiotics, as there don't seem to be any negative effects.

Very off topic, but.. did you explain how you recovered from CFS somewhere?

Healthy balanced diet over time, with a side of exercise.

At least when it comes to diet: sauerkraut, kefir, vegetables/leafy greens (dirt has good bacteria and some of it always remains on vegetables).

For me, it helps to cut out sugar. I cannot say that I suddenly feel like a new person or anything after a while without sugar, but there is definitely a lift of my my baseline mental stamina, when it comes to handling everyday situations.

Sleep also improves without sugar. That may be the cause also.

> 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.

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

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

Havok-wreaking or not, that microbiome is effectively part of the gut/brain.

Thought experiment: What would Dawkins say about gut/brain memetics? How do those "ventremes" propagate?

Being on long term antibiotics is a big issue.

Nice read!

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