Pushing back on the definition of normal body temperature | Hacker News Reader

Pushing back on the definition of normal body temperature

wired.com

62 pointssndean42 comments

I had heard that 98.6 °F was the result of rounding to 37 °C before converting, and that maybe the actual temperature is a bit lower.

This article mentions 97.7 °F, 99.5 °F, and 100.4 °F, which also look like they were rounded to the nearest half-degree Celsius. Some numbers might not have as much precision as it looks like.

Probably, although I don't understand why 37.

In Europe (at least in post-soviet countries I can speak of), _everyone knows_ (c) that the body temperature should be 36.6, which is 97.9 F. 37-to-37.5 is kinda beginning of a fever already.

I remember it as 36.4 but .6 could also be. Indeed, my mom at least always considered 37-38 elevated and 38.0 and above is a fever.

I read something about how the european temp is based on different testing, under the arm rather than under the tounge.

My dog's vet has a very cool toy. IR temp through the eye. Temp of the optic nerves, close to the brain.

The wikiepdia article on body temperature is interesting. You can get different numbers depending on the language:

- Arabic/French/Polish/Turkish: 37 °C

- Chinese: 36.8±0.4℃

- English: 36.5–37.5 °C

- Italian: 36.5 °C

From my own experience, people say:

- France: 37 °C

- Korea: 36.5 °C

source: https://en.wikipedia.org/wiki/Human_body_temperature

In my experience in France everyone © says 37,5°

Spain: 37°C

Polish version doesn't say 37°C is normal. It says that "latest research shows that average temperature of a healthy adult is 36.8°C". However it also notes that in Poland and Russia the ideal temperature was considered to be 36.6°C, which is what I remember too.

A great podcast on the subject:

http://freakonomics.com/podcast/bad-medicine-part-1-story-98...

TL;DL: The guy who came up with 98.6 was using inaccurate equipment.

My normal temperature has always been 97.9, since childhood. I usually feel a little sick at 98.6. When I tell doctors and nurses this, most are unsurprised.

It's interesting that the medical profession won't revisit this issue in a scientific way.

Well normal tempature has always been known to have a range. My normal temp is always 96.8 almost around the clock.

The BIG issue is when a fever begins which was always 101.5. My son had chemo with a port. Any fevers was a automatic 48 hours in the hospital getting cultures and antibiotics. I would start packing my bag when his hit 100. I knew it was going to be 101.5 within the hour. Now this means we can have people going in to the hospital sooner for fevers.

Medical professions have known for a while that body temperature varies greatly. It's the layman that are stuck on the 98.6° thing.

The same person can be 97° at 8am, then 100° at 8pm and feel totally fine. But the next day they are 100° at 8am and feel awful. There are a lot of factors that go into determining a good body temperature.

How often are you taking your temperature?

In my country, the pediatricians almost uniformly recommend lowering sick child's fever with cold towels or lukewarm showers. I never understood what is the point of lowering the fever below 103F. What is the evidence for this? What is the evidence for lowering fever below 104F or 105F?

Can someone knowledgeable comment?

I think that trying to lower a fever with cold towels is pointless. If your body decides it wants to be 40°C / 104F then it's going to do everything to maintain that. So by trying to cool the body with wet towels, you are just making it work harder, and you exhaust the kid even more.

Anti inflammatory drugs like Ibuprofen are the most effective way of lowering fever, it will actually cause the body to cool down on its own, and no wet towels will be necessary. Unless you have a really severe infection, in which case you should go to the hospital.

The only time when wet towels make sense if your kid can't regulate body temperature on its own anymore (eg. because of severe dehydration), but then you should really take them to the hospital as well.

Cold towels on the head is to lower brain temperature while allowing the fever to run elsewhere. Brain tissue is much more susceptible to thermal damage than the rest of the body.

Does putting a towel on the head really lower brain temperature? I thought that the brain is part of the body "core" that always has the same temperature.

Well, it’s the intent, I don’t know how effective it really is. But that’s where cold-towel-on-forehead comes from.

I'd think it'd be better to cool the neck to cool off the blood in the carotid arteries on the way to the brain.

Surface cooling of the scalp seems like it'd have a very limited effect on cooling the brain when body temperature blood is being pumped directly into the brain.

Your thought is in line with traditional thinking, but a 2015 study in the Wilderness & Emergency Medicine Journal found that cold packs applied to capillary-dense surfaces (cheeks, palms, soles) caused a greater reduction in body temperature that the traditional core/artery surfaces (groin, armpits, neck).

Source: https://www.wemjournal.org/article/S1080-6032(14)00405-0/abs...

I can believe that's true for lowering core body temperature due to the larger surface area of capillary blood, but the post I was replying to said that cooling the head is specifically supposed to target just the brain and not the rest of the body:

Cold towels on the head is to lower brain temperature while allowing the fever to run elsewhere

It still seems that if the goal is to cool the brain and not the entire body, cooling the blood on its way to the brain is better than surface cooling blood in the scalp that's going to soon leave the head through veins.

I think in the same way, however I never confirmed it. It also feels good, or less miserable, while you allow your fever to help fighting.

In italy "normal" is considered 36.5 C[1], but anything up to 36.9 C is OK, over 37 C it starts to be called "small fever" (febbriciattola), when over 37.5 then it becomes properly a "fever", nothing to really worry however unless it is 38 or over.

Personally I am always on the 36.8/36.9, whilst my wife is always on the 36.3/36.4 (we do a good average together).

The real issue is that (thanks to the ban of good ol' mercury based thermometers) I doubt the reliability of both the new "mercury free" glass thermometers (that in my experience tend to get "stuck") and the new electronic ones (possibly it is just that the common ones are cheap devices).

[1] normally "armpit" temperature measuring is used

> The real issue is that (thanks to the ban of good ol' mercury based thermometers) I doubt the reliability of both the new "mercury free" glass thermometers (that in my experience tend to get "stuck") and the new electronic ones (possibly it is just that the common ones are cheap devices).

Same here. Everyone I know hoards the old mercury thermometers. I don't particularly trust the electronic ones, because in my experience, cheap electronic sensors are mostly crap, and I have no reason to believe that whatever I buy at my local pharmacy will be more accurate than +/- 1 degree. And I trust the "contactless" ones even less.

Maybe this is why I have such a different experience : I've always heard of 37.5C as standard and fever starts around 38.5/39C, but rectal thermometers are very common here.

That explains it, temperature is going to be slightly higher if measured rectally than orally.

If anyone working at Feverprints sees this, please for the love of all things, disable your scrolljacker.

I feel hypothyroidism is more prevalent today than at any other point in human history. Everyone needs to check their body temperature regularly, it's a great metric.

Why do you think that?

there was a guy here on HN just a few days ago who said something I'd never heard before: "after losing 50+ pounds my metabolism is ruined forever, I cannot eat more than 1600 calories without gaining weight". I didn't know how it's possible without his body temp being permanently lower than normal.

I wonder what happened that caused those changes. Like, lots of people lose that much weight (myself included) and experience no changes. I see lots of pseudoscience on this I'd be interested in seeing what changes, what the contributing factors were, and how long it changes (is it permanent? Just a slow bounce back from the weight loss?). That's a drastic shift, and I imagine being cold is probably the tip of the iceberg in how a person changes if their metabolism drops that much.

> I didn't know how it's possible without his body temp being permanently lower than normal.

Pretty simple explanation. It's not possible.

If a person's body burns 1,600 calories a day, yes they will gain weight if they consistently eat more than that. If this person exercises more they will absolutely burn more calories.

Well, it's totally normal for your metabolic rate to drop as you lose weight. Think about climbing a set of stairs: when you're 50lbs heavier, you're doing a lot more work than you are after you've lost the 50.

He is obviously not properly counting calories.

It's hormones.

https://www.nutritionaction.com/daily/diet-and-weight-loss/a...

Look for the "Losing Weight" section.

The easiest way to look at this is to look at the cooling rate of a corpse. The slope of the cooling is pretty much linear as long as the ambient temperature is much lower than body temperature (for example 20 C vs 37 C). This allows you to calculate the amount of energy necessary to maintain body temperature. Convert that to kcal and this gives you the minimum number of kcal you must eat.

I've actually done it before (and even wrote a comment in HN with the results -- though it was a long time ago and I don't know if there is a way to search comments), but it takes more time than I have now. Unless my memory is incorrect or my calculations faulty, the answer is that it's very, very unlikely that a person who is over about 50 kg would be maintaining their weight with 1600, even if they were doing no exercise at all. Unless they are living in a very hot climate, it appears to be thermodynamically impossible.

Fun fact: I just searched my gmail for the word "corpse" to see if I emailed that calculation to anyone. I got 19 unrelated results. What the heck do I talk about in email???

There is actually one other variable (that I'm aware of) that's unaccounted for: the amount of nutrient absorption from the food. "Calories" in food are measured by burning the food and measuring the amount of heat given off. This value is multiplied by a kind of fudge factor to approximate how much of the nutrients are absorbed. According to a quick Google search, 98% of carbs, 95% of fat and 92% of protein is absorbed by the gut. So if we imagined that someone became super absorbent, they might require up to 8% less calories. But not enough to significantly alter calorie counting.

I considered replying to the original poster of that comment, but decided that they probably weren't in the mood to receive the news. Almost certainly they are missing things in their calorie counting. On the plus side, if they are getting 1600 calories consistently and maintaining their weight, then their error is systemic and might not matter (i.e. the actual value is meaningless as long as it is consistent -- they can still go down to 1400 calories and lose weight).

I've helped quite a few people lose weight before and it's pretty easy to overlook calories -- especially from fat. I had one friend who ate a really modest amount of food every day: typically a bran muffin (with butter) and coffee (with cream) in the morning. Half a subway sandwich (the kind with lots of different kinds of salami and mayonaise), a small bag of potato chips, and a bottle of sweetened ice tea for lunch. Pasta (with a cream sauce) and a salad (with dressing) in the evening. No desert, but the grand total number of calories was astounding -- pushing 3000 kcal per day. It's really, really easy to do.

It seems you keep your corpse related conversation mostly to email: https://hn.algolia.com/?query=mikekchar%20corpse&sort=byPopu...

As someone who's quirked the odd sceptical eyebrow at base metabolic rate charts, that's a helpful way of looking at it. Thanks!

> there was a guy here on HN just a few days ago who said something I'd never heard before: "after losing 50+ pounds my metabolism is ruined forever, I cannot eat more than 1600 calories without gaining weight". I didn't know how it's possible without his body temp being permanently lower than normal.

Whether or not your diagnosis is correct, how does that justify YinglingLight's claim (https://news.ycombinator.com/item?id=17910631) "I feel hypothyroidism is more prevalent today than at any other point in human history."?

> "hypothyroidism is more prevalent today than at any other point in human history"

Possibly because it was only discovered a century and a half ago and it's easily measured in the modern era? Plus, two hundred years ago it would have been "cold and tired all the time", which I kind of think was the default state for humanity.

Sounds like what would have been called a “weak constitution”.

Which was everything from hypothyroidism to depression to coughing up blood.

> I feel hypothyroidism is more prevalent today than at any other point in human history.

What makes you feel this way?

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