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Hunger Is a Gatekeeper of Pain in the Brain (nature.com)
165 points by Semirhage 9 months ago | hide | past | web | favorite | 104 comments

Early comments make me think people didn't read the article. Short summary: hunger reduces long-term inflammatory pain but reduce short-term acute pain was not reduced.

When I first read the title I thought of my observation with the migraines I get. Personally, migraine pain only onsets when 'everything is ok,' in terms of safety, stress, food and hydration; but the other symptoms will start at any time.

For example, while rock climbing once, I was getting down from the top of a mountain, seeing those 'squirlly refractive light worms' in my vision that some people with severe migraines get. I had all the symptoms of having a migraine--and was lucky I didn't die on that mountain--but the debilitating pain only came when I was down, in the car, away from danger, with food and water. This is how it always is.

Given this experience, I believe there must be a lot more to the psychological-physical aspect if interpretations of pain than what is shown here, and personal experiences may be why others are jumping to conclusions.

Also: those poor mice

> For example, while rock climbing once, I was getting down from the top of a mountain, seeing those 'squirlly refractive light worms' in my vision that some people with severe migraines get. I had all the symptoms of having a migraine--and was lucky I didn't die on that mountain--but the debilitating pain only came when I was down, in the car, away from danger, with food and water. This is how it always is.

I also suffer from migraines and I've tried different "tricks" to get rid of them or stop getting them altogether. Thankfully, I only get them ~2-3 times a month. (How some people live with chronic migraines is beyond me.)

I just wanted to say that I've also noticed this pattern. I have never gotten a migraine in a high-stress or high-stakes situation -- for example, I often get them in the car (maybe attributed to some kind of motion sickness) but never while actually driving. As a side note, I started drinking green tea 2-3 times a day which has decreased attacks by ~60% (I keep a log).

I wonder if that's due to the coffein in the green tea? Too bad I'm very sensitive to coffein and often can't sleep at night when I take coffein too late during the day...

What kind of green tea do you drink? I've read that there are very different levels of coffein in the different green tea types.

For me the number one trigger was caffeine, but because I'd never had that much, doctors just said it was probably stress, so I didn't eliminate it. Also because this all happened when I was a kid, I didn't have the wherewithal / knowledge to try an elimination diet. I was an anxious kid so my parents just accepted this "diagnosis" of stress as the main trigger (it definitely is one factor). I cut out caffeine to help me sleep better (after about 14 years of migraines of varying frequency and severity), and found my baseline (monthly, moderate severity) migraines almost completely vanished. Now I only get them if my sleep or food schedule or amounts are seriously disturbed.

Not sure if it helps, but apparently tea, especially green tea contains more l-theanine. This counteracts the jitters you get from coffee. Maybe a supplement would help.

Since you seem to be German, just a note: "coffein" in German is "caffeine" in English.

For me it's definitly tied to food. Life hygiene in general, but 80% food.

> seeing those 'squirlly refractive light worms' in my vision that some people with severe migraines get

Those worms are simptom that the migraine is coming, I had terrible headache several hours after I saw this light worms.

The medical name for the light worms is "scintillating scotoma". The Wikipedia article includes some artist's impressions:


Same here. I get visual disturbances that alert me to take the sumatriptan right away. Sometimes there will be no immediate migrane but given how incapacitating they are when they do happen, I medicate whenever I experience the black and white mirror ball start spinning.

I get these about twice a month, but luckily never headaches afterwards like some. After some googling it seems to be: https://en.wikipedia.org/wiki/Acephalgic_migraine

I wonder if there are people who overeat because of chronic pain.

Anecdotally, I find the dopamine hit of eating (a lot unhealthy food) is a worth more to me to any dampening effects.

Because while I might be in slightly less discomfort, I'm still in discomfort but also hungry...

I am sorry I can't parse this. You rather eat and keep the pain?

My parsing is that full + more pain > hungry + less pain. That is, the marginal benefit of eating is of great enough value to offset whatever additional pain is experienced.

Yeah, exactly. I don't know why I worded my original comment so weirdly.

I have chronic pain triggered by/related to eating, tied to celiac, dysphagia and maybe gerd. The odd thing is the pain is relieved while eating and 5-10 minutes afterwards, and in the past the discomfort used to spur me to keep eating.

I can’t really say the pain is lessened by hunger, because I spend plenty of time hungry and also in pain (I’ve lost 45 lbs since Jan 1). Hunger is enough to spur me to eat, despite that it’s almost always miserable later after I eat. Desire to not starve, or eat when very hungry, is one of the strongest urges, though, which would seem to overcome pain. Perhaps that’s precisely what they mean. I’ll be observing my own sensations in relation to this.

it would be other way around, they will eat less to dampen chronic pain.

The thing is, with health, if the effect of you action are not immediat, you are much less likely to do the right thing.

E.g : i know that if a drink a lot of raw milk i generally get a migraine. But it happens 24 to 48 h later. So i still drink milk from time to time because i'm not punished immediatly. It's future me's problem.

I imagine they'd put off eating as long as they could, and then give into the hunger.

I am a chronic sufferer, and in attempt to reduce my dependancy to opiates and opioids I put myself through a constant cycle of withdrawal. When I'm coming down I often have a craving for sugars and over eat. When high, I can go days without eating if not checked by a loved one. Overall I have lots a great deal of weight (including muscle mass), but I am very diligent about my diet. Others my find a craving of the sugars (in combination with a less than optimal diet), will result in a weight gain of fat and a reduction in lean mass. That is of coarse, if they go through times of withdrawal...

The article says hunger damps pain, not satiation.

Would you consider depression or lack of affection a kind of chronic pain ;) ?

Ah, the old causey-effecty switcheroo.

"The body’s basic needs include a timely supply of nutrients and the avoidance of tissue damage, which are signalled in the brain by hunger and pain, respectively. But these needs cannot be fulfilled simultaneously, because their resolution involves mutually exclusive behaviours."

Hold up. Why are these mutually-exclusive? Is nutrient intake not a subset of tissue damage avoidance?

I think I get the gist of what these sentences are trying to say (acute pain takes precedence over hunger, which takes precedence over chronic pain), but that's not what "mutually exclusive" means.

I took it to be in more evolutionary terms:

* If you’re hungry you need to move to find food

* If you’re in chronic pain you need to rest to heal

Consuming food is an inherently inflammatory process. Could this not explain the results?

What does it mean for eating to be an inflammatory process? Is a specific part of the body being inflamed? I keep reading news about inflammation but it's never been clear to me what it's meant when articles say that such and such activities reduce/increase inflammation.

Fasting is known to reduce inflammation

If you have persistent stomach pain not eating can sometimes do the trick if you suffer from digestive inflammation. The inflammation can be triggered by eating the wrong combination and or quantities of certain foods.

When I eat certain foods I have to blow my nose. Is that an immune response? Dad also had this problem.

Source / support?

I'm curious if the word, "hunger" is a poor choice in comparison of using "lack of food" and because I rarely eat in comparison to most people. I've become accustomed to not having hunger overtime as a result of fasting and otherwise one meal per day. I do believe the gateway of pain is true.

I've done the same over many years, and can confirm being accustomed.

I have very different sensations now signalling "lack of food" and "craving for stuff I don't need", and the latter isn't as persuasive anymore.

Great point, fasting over a period of time lowers Ghrelin

Nice that the very old natural medicine knowledge of starving and chronic pain reduction is confirmed. Unfortunately the exploration of old natural medicine knowledge is not well funded because there is no money to earn.

so incoming pain signal is filtered through low-pass and high-pass filters, the intermediate output from the low-pass is modulated by hunger and then added to the unmodified high-pass signal. this sum is the effective or subjective pain signal.

perhaps this could be used for online learning neural networks (with neural plasticity): goals are eventual and dont need to be accutely achieved upon the moment of forming the goal (i.e. feeding can be postponed), while punishment of the neural network should be accute in order to focus on the problem while any information related to the problem is still present in the brain.

I think low-pass/high-pass is sort of a misleading simplification. When they say "chronic" pain they're referring to inflammatory pain, which is distinguished from "acute" pain by its source, not its time course. (I think. Not a biologist.)

Different sources might use different time codes. Anyway, inflammation likely attacks all kinds of sensors and perhaps nerves directly, so the signal is noisy, and the high frequency constituents very unstable. Whereas functioning receptor networks likely fire in ensemble, so that signal should be kind of clear. The functionally intact rim of an inflammation is a comparably large area, so that would correspond to a low frequency signal. Although, it's much more complicated, surely, I wouldn't know.

Also, hunger after a long time becomes a dull feeling, too. Less energy -> longer time to light a synapse.

"Our minds are like our stomachs; they are whetted by the change of their food, and variety supplies both with fresh appetites" --Quintilian

This is expected: if you get very hungry then food acquisition is more important than avoiding relatively minor bodily damage. If damage is severe, then it can override the need to get food.

If it were not this way we'd be pretty rubbish at surviving.

Somewhat related recommended read: Hunger (Knut Hamsun)

[1] https://www.goodreads.com/book/show/32585.Hunger

Is it possible the particular rat-food causes inflammation? I'd imagine whatever they're being fed isn't their natural diet (i.e. organic raw meat etc)

After reading Peter Singer's Animal Liberation, I can't help but recoil in disgust at what it must have taken to produce the results for such a paper. Sure, this is interesting, but is it really worth the cost? Did the researchers or those who funded the research even reflect on it?

It's a one-time cost for knowledge that will have benefits indefinitely. I don't eat or wear animals, but I'd holocaust a million rats to solve the opioid epidemic.

Is the barrier for you species difference?

For example, medical insights provided by Nazi scientists, and to a lesser extent Japanese ones, were provided by tests on human subjects with often fatal results.

> Is the barrier for you species difference?

I haven't met a person for which this isn't true.

From my conversations with other people, the hierarchy of care is roughly:

Humans > large mammals > small mammals / cephlopods > birds / large reptiles > small reptiles / fish > large insects / trees > small insects / spiders / plants > yeast / fungi / bacteria

For me personally it's:

Humans > tool-and-reason-using animals (certain primates, corvids, cephalopods, cetaceans, etc.) > other animals in descending order of perceived capacity to suffer > bivalves > non-animal kingdoms.

Same here, it's why I cannot justify getting offended by people eating dogs when I eat pigs which are about as smart.

That classification also made me stop eating octopus even though it's one of my favorite dish.

Dogs and cats were domesticated as companions.

Pigs and cattle were domesticated for food.

I think most people's feelings toward these animals have deep evolutionary roots.

I don't think it's evolutionary at all - people who associate with some animal types convince themselves they're in a bilateral open relationship (the animal is choosing to be their friend), or even adopt a mental attitude where they use the animal as a proxy for a human infant.

This seems the result of socialisation in to that behaviour.

In the UK, outside food chain fraud, we don't eat horse, but plenty of other countries do - I don't think that's because we evolved differently.

I don't believe it's entirely a trick of the mind. There is a difference between animals which have been selectively bred to perform social roles and ones bred for food. They actually do display more social traits because they've been bred that way.

Not generally, however it's possible to buy horse meat from some butchers and in fancy restaurants. It's not as taboo as eating cats/dogs.

I didn't think horse was even legal, I've never seen it on sale in UK.

Totally legal though:


Yeah, although a life long vegetarian I've done a small amount of work with systems for butchers. Personally, I agree with others in this thread that eating pig is really no different than dog, cat etc. looking at things objectively. Being a soppy old Buddhist I try hard not to hurt any living creature.

I'd agree that from a position of inferred intelligence implying a mind is present then the morality is similar.

I think there are moral implications of dogs and cats having been bred as domestic animals; probably also there are tertiary implications through the differences in resources and methods needed to farm them (though these would presumably reduce as the animals were adapted to be cattle).

Meta: I know self-deprecation is a common pastime for us Brits but standing by your moral convictions to preserve all life is a noble endeavour, not soppy, and probably the greater for the wisdom that usually follows age.

Thank you for your comment, spot on about our British reservations. Also interesting point about cats and dogs being domesticated. I'd say to a large degree most animals farmed are in some way domesticated and wouldn't be able to survive in the wild as well as you would think. I know scrub bulls and other 'estranged' animals can thrive if the environment allows, but most pigs say wouldn't survive as well as wild boar do.

Doesn’t it make more sense to be upset at people eating pigs and dogs? Same here about octopus too, although it was never my favorite, I won’t touch the stuff. Pigs, dogs, cats... I try to avoid eating anything that can out-think a toddler.

This is more the line I was going down - I think in the future it will be difficult to justify, morally, the killing of any mammal for its meats. Especially when grown meat alternatives become affordable.

I say this as a staunch carnivore. I just don't see how it's morally sustainable. What if we develop methods of chemically induced greater intelligence, and a Peta activist goes to a farm and injects it into all the cows? Shit like that are what I think will eventually drive the world to vegetarianism. That or species extinction...

People don't preference other people who have higher intelligence. I find it hard to imagine they will forgo eating in order to preference other species of higher intelligence.

There's a simple moral justification for atheists - morality is a human construct, we can ignore it when we find that useful.

What makes you a staunch carnivore, if I may ask?

1. I love the taste of meat

2. Cooking is my primary hobby. I am fascinated by the history and culture of it, much of which is based around meat

3. I lift a lot and can't hit my macros at reasonable calorie to protein to dollar ratio without chicken and eggs

4. I have worked on a farm and as a result, as long as I'm buying properly sourced meat (pasture raised, not factory shit) I don't feel much guilt as I have confidence the animal had a comfortable life by the normal metrics of animal life, and was killed quickly and with little pain.

I just woke up and saw this, going to briefly touch on these points but please don't take it as trying to argue or push my beliefs ^_^

1. Do you love the taste of meat or is it the texture of the meat + the taste of the (plant) seasonings?

2. If it is your primary hobby, you should dive more into cuisines that don't focus heavily on meat as a personal challenge (as well as trying to make plant-based versions of things), I think you'd find it a lot of fun.

3. You can, that is a common misconception but there are a lot of resources on the internet about this–on phone and precaffeinated but I can look later if you'd like.

4. This is a classic reasoning I hear, I think it is honorable that you try to eat humanely killed animals, but there are other issues (factory farming is more environmentally friendly, selective breeding causes health issues, can't be sure all farms are as ethical as the one you worked on, eating meat at basically any restaurant goes against your defense, etc.)

Need to walk my dog, make breakfast, and go to work but I am down to continue this discourse at both of our leisures–hope you have a lovely day :)

I agree. The only animal products I eat are bivalves, though I was vegan for three years prior and vegetarian on and off for a decade prior to that. I'm finally at a place where I feel I'm eating in line with my morals, which helps stave off depression.

If this is true then why does non consenting human experimentation happen ever?

In any case, hierarchies like that are almost totally arbitrary, like anything about a culture.

I'm just poking the bear here and seeing what comes out. Let's play with this more.

Yup, totally arbitrary. That's why I prefer the poetry yeast writes about the beauty of the universe and the pain of existence to that written by humans.

Is your point that only humans have culture? There is evidence of culture and learned behaviors in animals as simple as birds.

My point is that the hierarchy is ordered by increasingly sophisticated internal conscious experience. This is the least arbitrary thing ever when it comes to concern around suffering.

My argument was more that there is no association between a theoretical "hierarchy of care" and actual, real brain sophistication. If there were, people would for example eat cats before they ate pigs.

Cats don't have much meat, I imagine larger mammals are farmed because they're large. But inhibition to eating pigs would be larger than that for eating cats, I'd agree on that.

Sorry edit: I disagree strongly that there is no association, it's an 80-20 thing. 80% can be explained by real brain sophistication, with 20% explained by cultural baggage.

I didn't realize that was your argument. I'd agree with that.

"As simple as"--are you placing birds in a hierarchy?

Sure, a hierarchy of complexity. You don't think such a thing would exist?

Why are you trying to seek out a hypocrisy angle in my arguments? I feel like that's a somewhat boring way to go about this.

> why does human experimentation happen ever?

There are a lot of drugs that pass animal testing only to fail human testing. Ethics review boards are a pretty good, but imperfect way to moderate the harm of human experimentation.

> hierarchies like that are almost totally arbitrary

This hierarchy corresponds roughly to some mix of genetic, morphological and behavioral similarity. It's obviously not arbitrary.

> like anything about a culture


You seem to be amused by my assertion that culture traits like this are arbitrary. I'm guessing you also believe in universal morality.

Anthropologists that argue against universal morality are used to being derised and mocked, but I don't mind being a punching bag - please, feel free to present your evidence that the hierarchy of care is the result of perceived similarities, and how this must apply rigidly and universally across all cultures. That, for example, there was never a culture in all of human history that placed a less-human-appearing animal's value over a more-human-appearing animal... or even over other humans.

Because expiraments on humans can provide information that expiraments on other animals can't, and the information in question is information that we care about.

In addition, humans can consent to things.

Consent is interesting, usually poor people will get paid for it, in which case it's a sort of coerced consent.

"medical insights".

Japanese and Nazi human experiments were hardly scientific. Torture disguised as science does not produce reliable results.

Unfortunately not.

E.g. most of what we know about reactions of human body to extreme cold was found by Nazi scientists in quite unethical, but reasonably scientific ways, for entirely practical military purposes.

NB: I'm not finding a source with a summary of total Nazi human experimentation subjects, though eyeballing totals, it seems that both Germany and Imperial Japan had several thousands of victims in ttheir respective programmes.

Triggers: pretty much all of them.



There are other states too - USA did live human subject experiments with nuclear weapons, for example. Also they did biological experiments with people having some diseases, not curing them in order to watch what happened. Also non-consented administration of drugs.

I'm sure we, the public, don't know the half of it.

Tuskeegee, St. George, San Francisco, and elsewhere.

Modern ethics requirements were established for reasons.

Only as a matter of degree I suppose. For valuable enough knowledge, I'd support medical experiments on unconsenting human subjects too if it were the only option. But this is a very hypothetical situation; the former bar and the latter constraint are extraordinarily unlikely ever to coincide (they are very rarely met even separately).

That is the problem with these hypotheticals, yea. In what circumstance do we absolutely need to perform human experimentation on unconsenting humans to get results?

But because these are my favorite too-drunk-at-a-bar conversations I wanna give it a crack. Here's a couple things I think require human experimentation

1. Creative a definitive best-practice guide to child rearing. I.e., hitting yes/no? Shouting at yes/no?

2. Fully understanding primitive/baseline human psychology absent of culture, which could help us understand if there is for example biological morality, how to teach language, how languages form. Can't see how to do this without abandoning a child in the wilderness.

3. Determining best-case formula for human tribal organization. I.e. what's the most effective leadership traits, organizational schemes, rule enforcement mechanisms... Could be figured out with Vaults ;)

4. Is post-death ressurection possible and at what point? I suppose you can get consent before death, but does that count when that individual terminates?

Can you think of any more? What are your thoughts on what would be "worth it?"

Your first two examples don't even seem scientific, or at least incredibly difficult to structure as a study in a truly scientific way.

Reduce for simplification:

How do we scientifically demonstrate effective means of raising children without experimentation on children?

I was watching on YouTube a talk by someone on AI intuitions coming from brain research, and the presenter was casually speaking about an experiment where a cat was sitting there with it's skull open and electrodes inserted into the brain and how the cat did this and that and what they measured.

It is interesting to read people's views on animal testing. Some are very empathetic while others view every other species as inferior and worth nothing compared to a human life. Obviously the advancement of our species is important but we definitely think far too highly of ourselves when we consider how destructive we are to this planet and all its inhabitants.

This is no surprise when you have people think like that about other humans.

In what dimension do you measure hight of thought? I guess on the one hand this could be linked to the architecture of the brain, directly translating to some topological notion. On the other hand, you might simply argue that others and self are on two different planes of existence and that higher consciousness is not concerned with just self and emotions, but with thoughts of thoughts ... per se, on very high levels of abstractions. And as those thought models are, if the bayesian crowd is to be any judge, highly probabilistic, those thoughts are just hypothetical. So, you are just saying they harbour wrong thoughts. They (we) are painfully aware of the possibility, but not very precisely. Then, in absence of other viable theories, they run with it.

In effect, I guess, if they have a low opinion of other creatures, they might not have a high opinion of themselves.

Hardly surprising when you consider that, historically, people considered other human beings worth nothing compared to their tribe, race, or religion.

If this sounds "too painful for the animals" to you, then other things done routinely in medical research would be 100x times beyond "pure torture" or "hellish" to you, meaning your cruelty threshold is waaaaay dis-calibrated.

Thankfully researchers have learned to "forget describing" the painful effects or use "over-technical description of procedures avoiding the perceived pain by animal subjects", so they can actually not be noticed by people like you, and carry on working on things like curing cancer and other important stuff. Also, the "is it really worth" question is the dumbest thing to do in science - most scientific discoveries are valuable because of their unforseen and unintended consequence, so saving cures can come from a 10th level consequence of "pointless research" (that could have gone unfounded because someone like you might've said "but is it really worth the cost [in animal suffering]?").

Better wake up and see the cruelty that is all around us first, including abundant human-to-human cruelty everywhere, and adjust your cruelty-tolerance threshold accordingly!

What is the alternative?

Performing such experiments only on humans, who are capable of consent, or not performing the experiment at all, and finding other ways of understanding the world that don’t involve doing things to animals that we consider ourselves too civilized to do to humans.

If you see it as a sacrifice, yes.

This can help a lot of people for a long time.

by the time you've gotten thru grad school, you've most likely have accepted the dogma of animal research. then there's little time for pause as its a mad dash for collecting good data, grants/funding, publishing. of course some funding agencies (NIH) have lab inspections but these can be real or a farce depending.

If you keep reading on the topic, you might reach the conclusion not that you should sacrifice your incremental well-being for the sake of animals', but that you should stop sacrificing your well-being for the sake of other humans'. Utilitarianism is internally consistent but inconsistent with most humans' (and animals', but they are instinctive not thoughtful about it) deepest sense of self.

That is a really creepy, skeevy thing to say when we're talking about painful medical experiments.

Eating disorders and self-harm seem to go together a lot so it make sense that there’s an underlying connection between pain and hunger.

Even those with eating disorders who don’t directly self-harm often state that their behaviors are motivated out of a desire to harm the self. This is very relevant.

Except that the paper seems to find the reverse connection - self-harm is typically acute, and this is not inhibited by hunger.

Reverse that a bit more: self-inflicted acute pain overrides/inhibits hunger.

Not all self-harm is acute. For example, eating junk because you hate yourself is not acute.

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