If X had been proven good for your health with little room for doubt, it would have reached the ears of me or my peers, because I can't imagine something being definitely good for everyone and not being adopted into standard health practices.
You might be interested in Inadequate Equilibria, which is a book-length treatment of this sort of reasoning and when it is or isn't effective. While I think it does rule out, say, that Cheerios grant you immortality, I don't think it rules out things like "SAD can be effectively treated by more light" or "many people can get an extra hour a day by increasing their sleep quality with melatonin" or "you should sleep with a window open to have lower CO2 exposure."
I imagine that there are things that doctors know about, but don't actually try; The Last Psychiatrist's experience with Ramachandran's Mirror seems relevant here. The Epley Maneuver is taught in medical schools and the Reddit Tinnitus Cure isn't (as far as I know), and so even presented with a patient with tinnitus after having seen that video a doctor might not think of suggesting it. [Of course, people also comment that the Reddit Tinnitus Cure doesn't work for them, so who knows what the actual effect size is, or what other parts of the technique are essential and not adequately explained; one comment claims that you need your palms to actually have a tight seal with your ears, for example.]
I imagine there are even more things that doctors haven't heard of yet, either because they haven't been discovered or haven't been applied to that problem yet. (Like, even of currently approved drugs, do we have all the sensible off-label uses mapped out?)
Hmm, fairies and trolls are not at all like a "vitamin X". There are plenty of supplements that are known to have real positive effect in many cases. And we still know so little about human body and mind that there could be still plenty of low-hanging fruit waiting to be plucked. As for fairies and trolls, we know that these are artifacts of the human tendency to anthropomorphize everything, and there is not a single member of the reference class "not human but human-like in appearance and intelligence". We also understand enough of evolution to exclude, with high confidence, species like that. (Including humanoid aliens, whether in appearance or in a way of thinking.) But we cannot convincingly state that some extract of an exotic plant or animal from the depth of the rainforest or the ocean would not prove to have, say, a health boost on a human. The odds are not good, but immeasurably better than those of finding another intelligence, on this planet or elsewhere.
Of course, I didn't mean to group fairies and vitamin X in the same category and convey that their odds were comparable (the odds of the existence of fairies are surely many times lower than the odds of vitamin X being effective). I rather meant to showcase the heuristic by which I tend to group fairies and trolls into "artifacts of the human tendency to anthropomorphize everything" to dismiss them as imaginary, which I think is the same heuristic by which I tend to group vitamin X and Y into "sounds like bogus" to dismiss them as ineffective. Grouping these into "sounds like bogus" might be done with a lower level of confidence, but I think it still stands. If there were a line of people, each holding a branch of one of every exotic plant on Earth, waiting to ask me "should I try this? (without any further justification)," I would say no to all of them, even if there's a good chance that one of them could provide a health boost.
Right, that makes sense. One reference class is "does not exist except in a fantasy" and the other "do not try it on yourself until there is reliable published research".
If X had been proven good for your health with little room for doubt, it would have reached the ears of me or my peers,
There you made a slight of hand by exchanging good for health with "there's little room for doubt that it's good for health".
There were decades where people discussed smoking causing cancer and there was room for doubting that's the case. Your heuristics would have you finding no problem with smoking in the 50ies.
More recently it gets you to the former position of the WHO/FDA that the lack of studies showing effectiveness of cotton-based masks for non-medical personal is a valid reason not to get everyone to wear a mask.
Essesentially, you put wearing a mask in the US in April as non-medical personal into the same category as believing in Fairies.
There you made a slight of hand by exchanging good for health with "there's little room for doubt that it's good for health".
I guess it depends on how much that "room for doubt" translates into being adopted as standard practice (i.e. if doubting the efficacy of vitamin X leads to it not being widely adopted, I might not recommend it either), which leads to
Essesentially, you put wearing a mask in the US in April as non-medical personal into the same category as believing in Fairies.
Basically this - thanks for pointing this out because I agree that's where my heuristics would have landed me and what actually happened at first, and it's a big source of my discomfort with this reasoning. That said, why some things are widely adopted or not is generally not that clear-cut to me (e.g. was the reason the lack of evidence or to save masks for healthcare workers?), which is why I just "go with the mainstream flow" in many situations in which I don't know better. I feel I'm starting to reduce the confidence I put onto health organization/standard guideline statements just because they're standard, but I'm not sure if there's something else in heuristic-space I should use to anchor (e.g. believing in Z person?) before getting more information.
That said, why some things are widely adopted or not is generally not that clear-cut to me (e.g. was the reason the lack of evidence or to save masks for healthcare workers?)
There was a lack of evidence (in terms of how EBM sees evidence). There was good pathophysiological reasoning to believe that the masks are helpful. The sane thing to do would been to perscribe masks based on the pathophysiological reasoning. The motivation of saving masks for healthcare workers was one reason not to engage in the sane action.
Looking at more information was not the key to the mask issue. The key was to actually engage in pathophysiological reasoning. I don't think you can improve on the mainstream flow by simply looking at more sources of information without engaging in reasoning.
The problem with wisdom is that it often can't be reduced to simply heuristics.
Mentally it's important to distinguish questions that you can easily answer from questions where it's hard to know things. The question about whether or not Fearies or Trolls exist is a question for which is easy to answer. In medicine you have a lot of questions that aren't easy to answer and where there no conclusive evidence to answer them either way.
For the reasons EY layed out in Inadequate Equilibria there's good reason to believe that it's often possible to improve on standard guidelines for medical questions.
Hueristical decision-making is quick and practical. Experts tend to have better hueristics, and are usually in a better position to speculate about unfamiliar or uncertain treatments than laypeople. One good reason to be a fantasy-forbidding expert is that there are massive asymmetries in unvalidated medicine. The potential upside of taking vitamin X is probably small and bounded. The potential downside is unbounded.
That said, given the long history of traditional medicine, there are probably some effective treatments in the alternative medicine canon that just aren't yet well understood. Intellectual modesty is important.
"Why don't you believe in fairies?" I ask.
Because I haven't seen them. (This might be fairly extreme, and rule out komodo dragons as well as dragons.* This can get more complicated easily: micro-organisms and people who say 'I believe in X because I saw it even if I couldn't touch it or take a picture of ti.')
*This has the benefit of protection against impersonal deepfakes if actually followed.
I believe in fairies! I do! I do!
...Except I don't, and neither do you.
"Why don't you believe in fairies?" I ask.
"What an absurd question," you retort, "it's because fairies don't exist." However, the many times when you thought something so-obviously-didn't-exist and were proven absolutely wrong suddenly pop into your mind. "Okay, let's do this exercise then. Why do I believe fairies do not exist?" For the sake of argument, let's equate fairies to diminutive humanoids with insect-like wings that can fly, and leave magic and wonder and weird golden powder out of the equation.
There are certain beliefs you hold about the real world that you deem incompatible with the existence of fairies. For instance,
The widespread knowledge of the existence of another species different from humans but with equal cognitive capabilities would mean that everybody would know about them and whole institutions would be built around them (maybe even countries).
If fairies existed but there was not widespread knowledge about them, it wouldn't take long for them to gain worldwide recognition after their discovery. The only way that would not happen is for the existence of fairies to be intentionally shrouded in secrecy, or for them to not have been discovered at all.
Even if the existence of fairies could be kept secret, it would be extremely rare for nature to spontaneously generate humans AND fairies. Given the extreme likeness and cognitive abilities of fairies and humans, humans would likely be closer to fairies than to any other primate. The divergence would have likely happened very recently, after nature invented big smart human brain, so you cannot help but wonder what selective pressures and coincident random mutations could have led to such a drastic reduction in size and change in function (wings) in such a short time.
"Whew," you think, "I can say for sure now that fairies don't exist." Your belief in the nonexistence of fairies actually paid rent. "But, did I really have to go through all of this just to prove to myself that fairies didn't exist?" Never in your life did you need to go through this tedious exercise to actually believe fairies didn't exist. This is the first time you had even thought of these arguments. Why exactly, then, did you believe that fairies do not exist?
I would place my bet on two reasons:
Everyone else seems to think that fairies don't exist, with extremely high confidence. You're pretty sure everyone around you would be willing to bet $100,000 that fairies don't exist, so you would be willing to bet as well. It would be extremely surprising for you if someone with a sound mind would be unironically willing to bet a large sum of money in favor of fairies existing.
You do not believe in fantasy mumbo-jumbo. Fairies, along with wizards, dragons, mermaids, gnomes, elves, half-elves, half-elf-half-gnomes, quarter-elf-quarter-gnome-quarter-elephant-you-get-the-idea's are all children of fantasy stories, and it seems to you many times more likely that they were invented by some buddy with a florid imagination than Mother Nature herself.
This last point strikes you as especially convenient. If someone comes in and asks you, "Hey, I know you don't believe in fairies, but what about trolls?", you would have to do that exercise all over again but now specifically for trolls, and the arguments for fairies do not necessarily apply for trolls (trolls might be non-primates, for example). That is, if you couldn't invoke the "it's all fantasy" card and be done with all those possibilities in one swoop.
I'm a medical graduate, and recently many people have come to me to ask if "taking X is good for my health" or if "I should eat Y in the mornings." Maybe the ideal response is "I don't know, but let me get back to you after going through the available evidence." Unfortunately, scholarship is a time and effort-wise costly endeavor, and there are other topics I would rather prioritize being scholarly on. So I start crafting my fantasy card with:
If X had been proven good for your health with little room for doubt, it would have reached the ears of me or my peers, because I can't imagine something being definitely good for everyone and not being adopted into standard health practices. The same applies if huge effect sizes had been seen for X, even if they did not apply to everyone.
X strikes me as more likely invented by a tradition not sufficiently grounded on empirical observation.
And then I slam that card on the table and proclaim "I don't think it's going to do any good," whether you ask me about vitamin X, fairies, or trolls. But then I come across topics like these getting good evidence reviews and signal-boosts, and I get confused because "what supplements should I take" was exactly the kind of question that would make my fantasy detection alarm go "ding".
I can always increase the precision of my fantasy detection (with the aforementioned scholarly costs), but I'm left wondering if having that fantasy detection boundary is even justified enough. I think it is. Not everything is worth investigating without enough of an intuition that it can be useful or promising. But I suspect this fantasy card is also why physicians can often come off as fantasy-forbidding grumps who say "no" to every sufficiently nonstandard treatment suggestion.