Some gut bacteria appear to communicate with the brain
bbc.com
bbc.com
The microbes that live in the gut can influence the way we feel in a bunch of positive and negative ways (could give sources but just google it).
Microbes are just little machines programmed by evolution. They're designed to optimally survive in a specific environment and get better at it over time. Most of the microbes in the gut have been with us for a long time so they've done some evolving.
Microbes don't actively think but their behavior and metabolism are still optimized by evolution. They can react to avoid being killed, to eat and to reproduce all without "thinking".
Each microbe also has a pretty specific diet. The microbes that enjoy greek yogurt don't often like chicken nuggets.
Microbes that could influence their host to consume food the microbes liked would be more fit to survive. Same thing for influencing their host to consume less food they dislike (or a competing microbe likes).
Influencing the host sounds complicated but it could be as simple as increasing the concentration of a byproduct when food concentrations of the environment are low. That byproduct could make the host tired or give them a stomachache or whatever else. With the brain connection, the possible range of these effects is broad.
If this trait was developed at anytime, it most likely got passed down to present day microbes.
Unfortunately the mainstream medical system has been completely unable to investigate or explain what is going on with my body, but anecdotally, the theory that there is a two way street between gut bacteria and the brain completely aligns with my experience.
I'm feeling better now, though my stomach still feels sensitive and I can no longer tolerate gluten.
I don't know what the cause was, but the gut-brain theory fits all of my experience and treatments aimed at improving my gut bacteria helped the most, and there has definitely been a strong connection between how my gut is feeling and how my mind is feeling.
Since you've had some luck with traditional medicines, I can share my $0.02 about the traditional system I'm somewhat familiar with. In traditional Indian folk medicine, the focus for practically everything seems to revolve around improving gut health. It's a common belief that tongue health is a reflection of gut health, so for example a coated tongue suggests a sluggish digestive system, and the physician will seek to address that before anything else. A lot of treatments also include required dietary changes (like avoiding certain vegetables).
I've never heard of this. Western medicine says "all the vegetables, all the time". What are some of the vegetables people told to avoid? Genuinely curious.
There is some evidence (in the sense of evidence-based medicine) that a low-FODMAP (fermentable *saccharides) diet reduces symptoms in patients with irritable bowel syndrome. [1]
As far as vegetables go, according to one site high-FODMAP vegetables include alliums and artichokes. [2]
It is worth noting that the authors of the linked review paper caution that it is unknown whether a low-FODMAP diet may have long-term adverse effects.
[1] doi:10.2147/CEG.S86798
[2] https://www.monashfodmap.com/about-fodmap-and-ibs/high-and-l...
Tried 100% only Chicken green veggies and sweet potatoes. A Month later I was out kayaking twice a week. No need for painkillers.
-- someone who tested positive for a hydrogen/methane breath test and just finished a 2 week course of Xifaxan
Just went to their site and it sketched me out a bit to read this.
https://www.visbiome.com/blogs/visbiome-vs-vsl-3/exegi-wins-...
($6.2/day without insurance coverage)
-----
Thanks! For anyone in Canada or USA wondering, I just searched and apparently you can buy it online now. About $2 a day: https://www.visbiome.com/collections/all/products/visbiome-c...
I had looked years ago and found it hard to get. Going to check with my doctor, might be something prescribable, which would either make it covered by insurance or at the least a tax deductible health expense.
Here's the Canadian link: https://www.visbiome.ca/collections/all
I want at least the name of each of the bacteria. Even better would be exact substrains. But if it doesn't tell me whether the main ingredient is a strain that produces histamine (bad for me personally - lots of headaches) or doesn't, this is not going into me.
I haven’t had it and can’t vouch for it but it’s not exactly some random probiotic.
https://scholar.google.com/scholar?hl=en&as_sdt=0%2C5&q=vsl+...
In case anyone is interested, link #3 finally has a list of what's allegedly in there without having to pay to read the 'study':
Four strains of Lactobacillus (Lactobacillus acidophilus, Lactobacillus plantarum, Lactobacillus casei, and Lactobacillus delbrueckii subspecies bulgaricus), three strains of Bifidobacterium (Bifidobacterium breve, Bifidobacterium longum, and Bifidobacterium infantis), and one strain of Streptococcus (Streptococcus salivarius subspecies thermophilus).
Mine's got:
Sachharomyces Boulardii, Lactobacillus plantarum, Bacillus Subtilis, Lactobacillus lactis, Bifidobacterium bifidum, Lactorbacillus rhamnosus, Bifidobacterium breve, Lactobacillus casei, Lactobacillus salivarius, Lactobacillus acidophilos, Bifidobacterium brevis, Bifidobacterium longum, Lactobacillus paracasei
I'm sure there's a study I can pay for that tells me what's in those, because they don't print it on the package either...
I put her on a prebiotic + probiotic diet (kaffir, yogurt, whole grains, dark leafy greens, etc) along with a basic probiotic supplement every night and now according to her, at least 95% of the symptoms have gone away. She’s able to sleep through the night now, better mood, better energy, better everything.
Not saying it will work for everyone, but it worked for her. I feel like so little is understood about the gut microbiome and modern medicine is letting people suffer needlessly.
Edit: just realized this sounds exactly like a paid infomercial lol
I check my B12 levels from time to time and they seem ok.
My hemoglobin is always a bit low and iron supplements don't seem to help.
What other things are common with long-term PPI use?
PPIs don't really treat GERD, imho it's one of those medicines to be used perpetually (good only for shareholders).
https://www.youtube.com/watch?v=qTzxfoL82n8 - good explanation why/how ACV works and why PPIs don't, iirc
I've seen vinegar recommended for GERD online before, but was curious whether there's much medical know-how behind it (studies or at least a clear theory of why it would help me vs. PPIs).
With a weak LES (lower esophageal sphincter) a lot of "just do this" GERD folk remedies don't work.
If you have low acid your digestion will be slower and if it's low enough you will develop bacterial infections. PPIs lower your stomach acid and can cause long term issues.
1/2 tablespoon in a large glass of water. Do not drink cider vinegar straight up. It will burn you. Literally.
I'm not overweight by more than a kilo or two, and I sleep on my back or side, so this doesn't match my case as much.
This condition is called https://en.wikipedia.org/wiki/Achlorhydria , and one of known side-effects of that is gastroesophageal reflux disease.
"The ideal pH for the stomach can approach 1 but should be below 3, where most pathogens cannot survive. When the pH rises above 5, several dangerous bacterial species are able to survive. Acid-blockers can increase the stomach’s pH ..."[4]
For lower esophageal sphincter to properly work, you in fact need normal levels of acid and proper acidity.[0][1][2][3] If you have the oposite, the sphincter does not fully close and boom, there's your heart burn.
The real mechanism of gerd is more complicated than "too much acid" or "acid too strong". I don't suggest you start drinking unwatered vinegar. I suggest you study the sources I've linked and only then decide for youself.
> I've seen vinegar recommended for GERD online before, but was curious whether there's much medical know-how behind it (studies or at least a clear theory of why it would help me vs. PPIs).
[0] https://www.youtube.com/watch?v=qTzxfoL82n8
[1] https://www.youtube.com/watch?v=HhUTAw6wcK8
[2] https://www.youtube.com/watch?v=nkRrlJFDFdA
[3] https://www.youtube.com/watch?v=i_UWDPrDR40
[4] https://chriskresser.com/how-to-cure-gerd-without-medication...
Did she at least tell the doctor "hey no worries my kid fixed it"? What did they say?
> Did she at least tell the doctor "hey no worries my kid fixed it"? What did they say?
The answer is no: I told her not to tell her doctor under any circumstances that she got armchair advice from her “kid” that actually worked because if I was a doctor who went through 10 years of med school + training, I would definitely be rolling my eyes if some senior came in and told me this story.
The point is, I haven’t dropped any probiotic brand names, I’m not hawking anything, I don’t gain anything by posting my little anecdotal experience. I’m just happy that I found a solution to a problem that has been torturing someone I care about for 10-15 years and wanted to share it so that it might help others in the same situation.
Edit: to be clear, there were other things too that helped clear up her symptoms that I omitted because my post was getting too long and because out of everything, probiotics seemed to be the biggest gamechanger. For example: first few months she also took DGL (Deglycyrrhizinated Licorice, to promote mucus secretion) 15 minutes before every meal, followed by a digestive enzyme taken with the meal (she doesn’t actually need these anymore and only takes it as a precaution if the meal is particularly starchy or high protein). Cutting out LES relaxers like caffeine, mint and chocolate helped. Also lifestyle changes were made in terms of physical activity. She still needs to sleep at an incline on a wedge block, but at least she’s not vomiting all over the carpet anymore.
Turns out it was Familial Mediterranean Fever and it just goes away in your early 20s. I was never diagnosed until many years later and I even thought a lot of my remedies maybe worked until then.
Digestive and autoimmune both are labyrinthine in potential problems and misdiagnoses.
No argument there, and I appreciate the warning. It definitely gives me no pleasure playing doctor and I’m very conscious of the risk of giving misleading medical advice.
The reason why I’m confident enough to post this is that it has already been more than a year now since the major symptoms went away. The effect of the probiotics was/is pretty definitive (she recently stopped taking them for about a week while on vacation and the symptoms started slowly creeping back, and disappeared again shortly after resuming). Also, there is pretty much no real alternative treatment aside from PPIs or physical LES surgery anyway. If there is indeed an underlying autoimmune condition though, I can’t see how this diet could hurt too much. But maybe that’s due to ignorance.
I’m so happy you overcame that hell.
It’s pretty clear that this (like 99% of internet advice) is all anecdotal evidence and again, I’ve made it clear it may not work for everyone. I’ve also mentioned elsewhere that I’m not a healthcare professional. But if my comment is able to help even one person escape the nightmare of not being able to hold food down and the sleep deprivation and depression that comes with severe GERD… then that’s worth one snarky linux systems guy yelling at me on HN.
:)
Interestingly, the body of research around fermented foods (kefir [sic], yogurt, kimchi, etc) seems to show more robust benefits than probiotic supplements[1].
[1] https://www.cell.com/cell/fulltext/S0092-8674(21)00754-6
You'd have to know what's already in your intestines, and the best we have are poop tests, one of which (uBiome, YC S14) famously failed and is being prosecuted as insurance fraud, so doctors probably don't want to get into that. (There are still going ones like Viome that might give you interesting results.)
Fermented foods aren't all the same too; yogurt is milder than kimchi for sure.
In other words, changing to what appears to be a more healthy diet (fermented food, high fibre and high nutrient vegetables etc) might have worked with or without the probiotic side of things.
I definitely agree that the connection between our gut and our health/behavior is going to be a very fruitful area of reasearch over the next 5-10 years.
I was suffering from reflux, switched to mostly carnivore diet and only get heartburn now when I eat or drink the wrong things. Tea does that to me, or the occasional piece of bread.
Also Depression went away, haven't done any gut micro biota testing, because it's expensive and I'm not rich.
My girlfriend suffers from similar symptoms (but less severe).
@myshpa posted a link above which I hadn’t seen before, that actually confirms many of my own independent observations: https://chriskresser.com/how-to-cure-gerd-without-medication...
What worked for her:
- 10-15 minutes before every meal, suck on a DGL (Deglycyrrhizinated Licorice) tablet. This will interact with saliva and cause the GI system to secrete mucus to protect itself from acid.
- During the meal, take a digestive enzyme that contains at least Betaine HCL, Bromelain and Papain which will help break down carbs and proteins and stop food from entering the gut half digested, which can cause gas production from fermentation.
- Take a probiotic supplement every night before bed (we’ve found 15 billion to be sufficient, but you can try ones that are less/more potent). If you need water to swallow, squirt a tiny bit of lemon juice into it first.
Diet-wise: Avoid things that will relax the LES such as caffeine, mint, chocolate, etc. Avoid anything with tomato skins and certain types of legumes (if you want to eat these, remove the skins). It can be difficult, but reduce sugar intake as much as possible. Try not to drink water while eating (it will dilute stomach acid) but if she needs to, its been my observation that a tiny squirt of lemon juice with water helps.
Eat fermented foods regularly like Kefir, Kimchi, Sauerkraut, yogurt, etc. These probiotics will need to consume fibre from prebiotics in order to not starve in the gut. Increase your intake of all kinds of high fibre whole foods. Kale, beans, broccoli, whole grains, potatoes, whole almonds, etc. Google “low FODMAP diet”.
Regular exercise is important. It can be something low intensity like walking. It helps stimulate the digestive system and gut activity. Do it before meals, preferably.
It can be counterintuitive, but I think the root cause of a lot of GERD symptoms is actually weak stomach acid. That article linked above summarizes it pretty nicely. If that’s the case, make sure your girlfriend is at least supplementing with vitamins C and D, plus a B-complex with Methylcobalamine. Low stomach acid can cause malabsorption of these nutrients and others.
Keep a log book. Every body is different, so every time there is an episode, be sure to record what was specifically eaten that day and then avoid that food.
Any other questions feel free to ask.
I don't need coffee any more to function and I finally feel full after eating - strongly so even.
If it's really the probiotics, then I regret never taking them before - especially after antibiotics.
Mmm. The root for the word “masticate” (the resin is used like chewing gum), and the “piney” flavour in Greek halva (among other things). Notably, a collection of trees on one Greek islands (Chios) were under threat from forest fire a few years ago[0].
For many of these gut health related issues, I think most people would be better off seeing a dietitian or even as you say functional medicine doctors. As Tim Spector has been saying, so many ailments resulting from the gut can be fixed through eating a more organic/wholefoods diet. This takes time and isn't easy to do.
The sad reality is that many doctors are operating with what data scientists would reject as missing or bad data, the solution (ignoring the money side) is to get them into a pattern of collecting more data and being better at analysing it.
Each microbiome is different, and I think until sequenced and analyzed, it is simply guessing on the part of patient and doctor.
Honestly if you have a typical software engineer's salary and no dependents, just fund some studies yourself. Do them in South America or some other place with lower compliance requirements.
Autoimmune protocol diet is amazing for resolving from food triggers.
I think your story has a lot of weight and I personally am very curious as I've had my own suspicions personally. Thank you!
An episode of extreme stress during the pandemic has left me with IBS-C.
Apologize for TMI.
Before: I ate anything, whenever, in whatever quantity body requested and was consistent 2-3x/day.
Now: my body just does not pass stool on its own anymore and I require a prescription for Linzess (highest dosage). Without it, I will bloat to the point of a visibly distended stomach and pass rock hard stool once every 3ish days. Being so bloated causes me to eat less and I shed 15lbs (145lb@6ft). Tried no fodmap diet, heavy on fermented foods for a while, xifaxan (in case of SIBO), prebiotics previously mentioned on HN. I've settled on Linzess daily + a heavy meat diet, with oats for breakfast. Too many vegetables and I get bloated. Most breads as well. Carbonated beverages make me into a balloon.
My symptoms were similar to yours. I discovered on my own that digestive enzymes blends with every meal kept things flowing for me. Abdominal massage helped too. But I didn't make real progress until I started working with functional medicine doctors and trying different regimens of supplements with their direction.
Thanks for sharing! Here comes mine.
> pass rock hard stool once every 3ish days.
I go once every 3 days, sometimes even 4, without any drama. I quite like the schedule and think it saves me a lot of time. I believe what makes it work is that I drink ~1.5 liters of tea every day, on top of the water I get from one meal per day plus some snacks here and there.
I used to be constantly bloated and extremely gassy. But no longer since I stopped going to restaurants and started eating home-cooked meals made from fresh ingredients. Turns out my stomach is just allergic to crappy ingredients restaurants like to put into our food.
I take zero medication.
Hope you find your way soon to better gut health!
Yes, "big pharma" has a lot of control, but medical research is not entirely driven by them, particularly outside of the US.
It sounds like you remade your gut biota via various paths. "Traditional" medicines are "medicines" when they get through a set of actual medical clinical trials, after which they are called "medicine".
The fact that you have given yourself some form of gluten intolerance/allergy does not exactly imply "success" in what you've done so far.
To be fair, Tylenol almost certainly wouldn't pass clinical trials today. Selling a drug OTC that so easily causes organ(liver) damage? Ridiculous. So would most NSAIDS-- as those cause stomach bleeding even in regular clinical doses. That also would imply that companies had an interest in testing natural treatments that may not sell well
The WHO on the other hand has been investing heavily in traditional and complementary medicine (T&CM) in developing countries as they offer "care that is close to homes, accessible and affordable. It is also culturally acceptable and trusted by large numbers of people". Interestingly, the use and research into traditional medicine is actually increasing worldwide. The US seems to be pretty unique, even compared to developed nations, in how little it values TM. The WHO report linked below points out that 100 million Europeans, 76% of Singapore, and 86% of South Koreans commonly use TM. It also points out interesting research like:
> Another recent study indicates that patients whose general practitioner has additional complementary and alternative medicine training have lower health care costs and mortality rates than those who do not. Reduced costs were the outcome of fewer hospital stays and fewer prescription drugs (31)
Interestingly, they differentiate TM from CM. TM being a country's actual traditional medicine system and the knowledge passed down across many generations (e.g. Unani, Ayurveda, TCM, etc) and CM being more like "alternative medicine" that is not part of a country's traditional system (anthroposophic medicine, chiropractic, homeopathy, naturopathy, osteopathy, etc; think your aunt trying to sell you essential oils)
Whatever medicine whoever is using at the end the best way to stay healthy is exercise, good clean living conditions and a healthy diet.
No need for medicine unless you are ill
I've heard that said before. Is it really true? I'd like to think we'd pull it off the shelves if it were really that bad. Looks like about 250 people are killed per year from overdose (accidents only, not suicides).
NSAIDs cause quite a lot more deaths than that, but it's possible they're used more heavily than acetaminophen, I'm not sure on the usage stats.
The best indicators of gut health are:
Minimum flatulence and burping, or at least being aware of what you put in contributes to what you off-gas; stools should be well formed, easy to pass, mid to dark brown, about the size of your index fingers and thumbs on both hands touching to form an elongated, and not malodorous.
"By definition," I begin, "Alternative medicine," I continue, "Has either not been proved to work, or been proved not to work. Do you know what they call Alternative medicine that's been proved to work? Medicine."
Chronic condition that has subjective symptoms at best? Doctors couldn’t care less.
There always is a gap between medical research and application which people have different opinions on. For example when it was found out that high cholesterol was bad for you, doctors recommend patients with high cholesterol to eat less cholesterol. Later it turned out that there was little correlation between eating cholesterol and having high cholesterol. The correct opinion supported by scientific evidence was considered alternative medicine for decades.
[1] https://www.dccv.de/aktuelles/nachricht/teuer-und-sinnlos-dg...
We know that a diverse microbiome might be healthier than a non-diverse one. Exercise, eat your fibers, legumes, fruit and whole grains. Avoid processed food. Enjoy some fermented condiments. Avoid alcohol.
In my opinion there being no evidence in either direction does not mean that you should not try it, especially if there is no downside and you have a chronic condition.
I assumed lack of evidence + non mainstream opinion = alternative medicine. Maybe there is a better word for cases like this where there is some evidence but no clear indication of causality.
[1] https://www.asianscientist.com/2017/10/health/liver-cancer-h...
Yes, I probably remade my gut biota. Yes, I was shooting in the dark, because the medical system flat out refused to help me. I had doctors laugh in my face and tell me I was making things up because I was too young to be unhealthy. Is that science?
Yeah, clinical trials are needed to evaluate some traditional medicines. But why aren't those clinical trials being done? It's not like Ayahuasca was discovered yesterday. And it's not like it's hard to access. You can literally make it in your own home. I'm struggling to understand why so many people these days insist that "not doing science" is actually "science" as if science is static and we don't need to investigate anything new because we already know everything.
And as far as me giving myself gluten intolerance, fuck off. I've been gluten intolerant since these issues began, before I ever considered anything outside of mainstream medicine. I didn't do this to myself. And in fact, it's another thing that mainstream medical doctors refused to investigate. I had to order my own lab tests to confirm.
https://en.m.wikipedia.org/wiki/Vagus_nerve
Also good to learn some self-massage for the abdomen, and diaphragmatic breathing too.
Ultimately the odds are that it's masking the symptoms in one way or another. Much like my cousin who went full into traditional medicine and claimed it solved all of her issues that she still has after downing a cocktail of 50 essential oils and whisky.
A few mainstream doctors prescribed medicines to relieve my symptoms without addressing the underlying root causes. You seem to think that's a feature of traditional medicine, but it's actually quite common in mainstream medicine as well.
Something is going on with the brain and my gut.
It's possible that it's endorphins being released to stop any pain ... but this is about 24 hours before the crippling cramps start, and it's more a mood shift than pain killing. Before this great 24 hour, I'm normal baseline okay state.
Some might say that you got it backwards and this would be preferably your "normal".
First thing I'd do would probably be to document in detail what you're eating on those days and if any pattern emerges. Try eliminating things, if there is any pattern. Sounds a lot like lactose intolerance to me. I used to have it, but managed to get rid off it.
What I did for a while was intermittent fasting (restricting caloric intake to a 6-8 hour window each day.) I did this unrelated to my lactose intolerace, because I hadn't considered that it might be 'curable'. After doing this for a month or so, I somehow forgot taking my lactase supplement for a while (I didn't even notice until some time later.), and curiously I did not get those lactose-intolerance symptoms anymore.
I'm not an expert on these things by any matter, but from my amateur-readings of the literature there are two forms of lactose intolerance: the first, and most common, is a genetic one where your stomach just doesn't produce enough (or any) lactase anymore, starting at a certain age. The second one is more controversial, but might be related to bacteria living in the gut, which populate on the stomach lining and prevent the gut from releasing lactase; and it - to me - seems like my calorie restricted diet has starved those bacteria out.
So I can't say for certain if the month of intermittent fasting resolved the issue of lactose intolerance for me (since n=1), but it sure seems so because I hadn't made any other major changes to my diet then (except perhaps that I reduced carbs, in particular refined sugars.)
You can make them by just blending ginger with citrus juice and tumeric, then filtering with a cheese cloth.
How do you feel the day after the pain? Feeling utterly exhausted afterwards is also a common symptom.
I usually get the migraine pain in my head, but I've had a few abdominal migraines and they sound very similar to your symptoms. Maybe something to look into.
Today's world of commercialized food (a few major foods/culprits in particular) throws inflammation at us in spades, and eating well has honestly made a huge difference in my life -- the most noticeable parts by far being cognition, energy, and mood. Every time I deviate from clean cooking and eating mainly whole foods, it's painfully obvious since my microbiome loves the new, healthier norm.
I would highly recommend this podcast (neuroscientist Andrew Huberman) if anyone wants to learn more about improving their gut health and the science and research that we know so far. https://www.youtube.com/watch?v=15R2pMqU2ok&t=4500s
True. But it doesn't cancel the fact that most preachers of detoxication and such are cranks.
The section in the book about fecal matter transplants (FMTs) and how they work blew my mind.
(Edit typo)
Obviously this could also become a population-level attack vector.
....I've enjoyed the first two episodes.
The notion that gut health impacts mental wellbeing is obvious. The specifics of it are less so.
Source on Ayurveda posits that palm reading is legitimate medicine?
Not really, they're more astrology based, not medicine, and no one is claiming astrology is factual in this thread. Also, they're clinics, not a source of any kind which is what was asked for.
But the podcast I watched, was here: https://www.youtube.com/watch?v=66hWntvp0_4
My impression is that there isn't a very good way currently of knowing ahead of time what if any probiotics might work well for any particular person.
My wife has done the same, and has discovered that the one that works for her is a completely different sort.
[0] https://www.goodreads.com/book/show/49088685-this-is-your-br...
There was an experiment in mice that showed some mice devoid of any gut bacteria had better bone density than the other experiment group.
This is interesting and might suggest some bacteria can cause bone issues.
There is a nervous system in the digestive system that is connected to the brain.
Therefore it is possible for a bacteria to evolve to influence the brain.
If it was possible for a bacteria to evolve to control their host then they would do so.
Therefore, they have done so.
For me it's a common knowledge and I use it quite often.
https://www.hopkinsmedicine.org/health/wellness-and-preventi...
This is, in fact, old hat
A Multidisciplinary Hypothesis about Serotonergic Psychedelics. Is it Possible that a Portion of Brain Serotonin Comes From the Gut? https://pubmed.ncbi.nlm.nih.gov/36137971/
Seeking the Psilocybiome: Psychedelics meet the microbiota-gut-brain axis https://www.sciencedirect.com/science/article/pii/S169726002...
Serotonin Reuptake Inhibitors and the Gut Microbiome: Significance of the Gut Microbiome in Relation to Mechanism of Action, Treatment Response, Side Effects, and Tachyphylaxis https://www.frontiersin.org/articles/10.3389/fpsyt.2021.6828...
I'll never think of my gut bacteria in the same way again.
Since we do not know much about how the brain works to begin with I guess that is as close as we can get.
I say we dont know much about how the brain works as a I take medication for depression.
The way that works most often is that you are given a pill that may work. You take it for between 2 - 26 weeks, depending on results. (some may have a fast negative effect) and then you tell your doc if you feel better. (Sometimes complicated surveys)
if it didn't work, you get to do it over again. and again and again. until you find something that works, give up or die.
then sometimes it stops working.
One place I know does a cool, I forget the proper name. They take a "video" of how your brain is "working" (at an extremely low resolution). then they compare what they find to knowledge about what parts of the brain should be active, not active etc. From this they hope to establish a delta between "normal" and you.
Then you get to take pills and you come back (after some times) they do the whole thing over again, to see if you are now closer to "normal" or not.
The goal then being to find a chemical that brings you as close to normal as can be.
It is highly appealing in that it would offer -some- scientific basis for evaluating the drugs aside from "How do you feel".
If it -actually works- I have no idea. It was far too expensive for me, and to qualify you have to not have taken any medication already. (that would mess up the "virgin" recording).
An interesting research project would be recording tens of thousands of people who self-reported no depression in the hope that some would develop clinical depression and comparisons could be made.
If we now mix in gut bacteria into the equation, I can imagine you somehow "insert" new gut bacteria into a person and then you wait for some time and tell the doc if it worked or not. If not you can get a different psychobiotics and enter the loop. Add in regular medication for depression the number of possible permutation would become huge.
(I like to include this link to a Standford lecture on the difference between "being sad" and clinical depression https://www.youtube.com/watch?v=NOAgplgTxfc)
If the point of your post is to say that the boundary is larger than that of the brain itself, but extends to the nervous system, gut bacteria, etc. then I think one could counter that all those things are relatively easily replaced by simulations and therefore don't need to be part of the brain in the vat to make the thought experiment work. A person can lose arms and legs and intestines and still be perfectly conscious.
If you say that the brain itself could be replaced by a simulation and not lose any qualities, then the brain-in-a-vat thought experiment doesn't really mean anything for you because there would be nothing special about a brain anyway, and the scenario is vacuous.
You can also lose parts of your brain and be totally fine!
I'm not sure this proves as much as you think, though I do tend to agree.
key word :)
In caveman days you had to wake up, triage the current environment for threats(weather, animals etc) and then once that was done you would go out and try to find food.
It makes sense that your stomach would take a back seat till the above had been taken care of. It would then trigger the hunger feeling to motivate you to focus on food.
https://www.youtube.com/watch?v=2mG7DbMQ_gM
Censor, downvote and otherwise dismiss without any intellectual pursuit. If that's what you did then it's an identity for you and evidence to the contrary won't matter.
If we are discussing gut/brain connection in one way why not in others?