Drinking hot liquids in the heat?

[Fish_Cheer]

It’s not a textbook, but at least it’s in German:

@http://de.wikipedia.org/wiki/Schluckakt

Beim Essen ist die Schluckdauer davon abhängig, wie gut der Bissen gekaut und mit Speichel vermischt wurde. Die Passagezeit durch die Speiseröhre beträgt etwa 8–20 Sekunden.

Says: When eating, the time it takes to swallow depends on how well the bite has been chewed and mixed with saliva. The passage time through the esophagus is about 8 to 20 seconds.

[Fish_Cheer]

And here’s a video: YouTube

[Quercus]

@constanze

Do you want a cite of where the sensor for core temp is in the human body, and what it tracks, or do you want a cite what behaviour affects it?

Well, it’s just that my understanding is that the main human core temperature sensor is in the hypothalamus, in the brain. [weak cite: “The hypothalmus contains not only the control mechanisms, but also the key temperature sensors.”] if that’s wrong, please correct me. And I find it hard to believe that something cold in the stomach or on the skin is going to affect the hypothalamus, and therefore the body’s thermoregulatory response, unless the body core temperature really is lowered. Any kind of link or explanation (in English, or possibly French) as to how that would work would be appreciated.

@constanze

[And of course, your body doesn’t heat up foods ‘because that’s how it can deal’; cold foods in contact with a warmer body are going to heat up no matter what the body does. That’s just how temperature works.

I’m not a doctor, so I don’t know if the body heating up food is a side-effect on the body being warm, or if it’s a deliberate effort to bring the food to the temp. where the enzymes will work. .

Again, I’m not sure what you’re saying about the body ‘heating up food’. Cold food in a warm stomach will heat up to the stomach temperature, just like cold food in a warm oven, or (below room temperature) cold food sitting on a table in the middle of a room. It’s not because of any process in the body; it’s just about temperature differences and the fact that the stomach wall isn’t a perfect insulator. Now, at the same time the body will cool down of course, but because the body is a lot bigger than the food, the body won’t cool down very much. And if somehow someone drank enough cold liquid to actually cool their core temperature, then it would certainly be a good thing if the body started trying to raise its temperature, right?
Anyway, I suspect the reason you feel warmer a little while after a cool shower on a hot day isn’t because your body’s thermostat has malfunctioned, but rather because your skin is better at detecting relative differences than absolute. So after being in the cool shower, the outside air feels much hotter, even though it hasn’t gotten any warmer outside.

[Irishman]

antonio107 said:

1. Is there any truth to hot liquids keeping you cool (or perhaps more simply, “comfortable”) in the heat?

2)If so, why is that so?

Thanks!

Coincidentally, I ran into this claim just this weekend. Also the claim that the warm water aids digestion because the body doesn’t have to strain to bring it to temperature.

Nava said:

@constanze

Apparently, the Egyptians used porous clay pots that kept water cool by evaporation, since the Nile river was close enough.

They don’t just keep water cool, they lower its temperature.

So they make it cooler than it started, and then keep it there.

Earl Snake-Hips Tucker said:

I also had a 3rd grade teacher who said that fanning yourself when it’s hot makes you hotter because “it evaporates your sweat, which is there to cool you down.”

Yes, sweat is there to cool you down – by evaporating! Unless you live in Houston, where the sweat is apparently there just to make you feel soggy, ‘cause the air is so wet already it can’t evaporate nuthin’.

constanze said:

Um, who said anything about heat stroke victim?? We were talking about normal persons! Heatstroke and Hypothermia are obviously extreme situations that require medical attention, not normal situations.

The point is that when cooling and heating the body really matter (affect your life and health), you cool with cold water and heat with warm water. Thus the principle is established that cold water cools and hot water heats. So if you think the situations of extreme cases are different than “normal situations”, it is incumbent upon you to explain and justify what the differences are and why the reverse makes more sense in those cases.

• Cold drinks do refresh for real, though. The effect on the body temp. is marginal, however. Even after enjoying ice cold drinks, doctors could measure a lowering of body temp. of only 0.4 C in their test persons. Moreover, this cooling effect lasts at best half an hour, according to scientists. Because the sensors in the inside of the body recognize this supposed temp. drop quickly and try to balance it out with more production of heat. With cold drinks you can therefore sometimes achieve exactly the opposite of what you want to achive with their consumption. Too cold can additionally damage the stomach. In contrast, warm drinks in summer can be quite sensible. Because the most effective against heat is the body’s own mechanism: sweating. The reason: it leads to a constant cooling via the skin. And with warm drinks the sweat production can be stimulated for a longer time than with cold (ones).*
  Translation by me

Trying to make sense of this, I can sort of see that if you spike cold, your body may try to adjust, which puts you in transition phases, rather than keeping homeostatic and thus more consistent cooling rate. But it seems dubious to want to stimulate more sweating. If your body isn’t trying to sweat, it’s because it is cool enough not to need to sweat. Ergo, the desired effect - being cool - is already taken care of. Sweating has undesirable properties to it (i.e. leaving you soggy, running in your eyes, etc), and is only moderately effective.

[Ice cream] starts out with 8 C, your mouth warms it to 12 C, the gullet to 15, and when it arrives (20 min. is the usual time from mouth to stomach for food!) in the stomach, it’s close to 20 C which is warm enough.

Ice cream starts at 8 C? :dubious: Ice cream is essentially frozen milk/cream - it has to be cooled below 0 C in order to freeze in the first place. That’s why homemade icecream freezers need salt to the ice. How is it 8 C to begin with?

http://pubs.acs.org/cen/whatstuff/stuff/8245icecream.html

This freezing-point depression is a colligative property arising from the sugars and salts in the ice-cream solution. As crystals of pure ice form, the solution’s sugar and salt concentration increases, depressing the freezing point further. Goff says that, even at the typical ice-cream serving temperature of –16 °C, only about 72% of the water is frozen.

What is the temperature of ice cream? - Answers

the temperature of ice cream is -23.15 degrees celsius

Yahoo | Mail, Weather, Search, Politics, News, Finance, Sports & Videos

The best temperature to store ice cream is between -5°F and 0°F. For serving, the temperature is between 6°F and 10°F (both are freezer temperatures, of course).

Those are deg F, or store ice cream between -20.6 C and -17.8 C, serve -11.8 C to -7.8 C.

I grant you there is some variance in the numbers, but they are in the ballpark for each other, and none agree with the numbers from your newspaper article.

Now I will concede that ice cream typically begins to melt a bit as it is being eaten, so the typical spoonful/tongue full (from a cone) is partially melted. I could see that bit being above 0 C. But spoonfuls typically also contain frozen ice cream. 8 C seems high - that is 46.4 °F.

But why are cold drinks a problem, then, you ask? First, dumping a load of ice cubes into a drink (maybe even with alcohol) can make it significantly colder than ice-cream.

:dubious: Adding ice into, say, a glass of water, can at most cool the glass to 0 C. It will not freeze the liquid. Ice cream, being frozen, will be colder.

Secondly, a drink can be guzzled down far quicker than ice-cream, so it has less chance on warming up on the way. Once down and still cold, you can cause “freeze burn” damage to the walls of the stomach, because the body doesn’t expect cold down there.

I will grant you that ice water flows down slightly quicker than ice cream gets swallowed. I don’t buy, though, that the difference is on the order of 20 minutes. I also have a hard time believing you can “freeze burn” your stomach from ice intake. While the cold temp may be in place longer than passing through the mouth, there is a mucuous lining in the stomach to protect from the digestive acid.

Thunderstorm moving in. Will submit now and continue in future post.

[Irishman]

Quercus said:

For that matter, I’m a bit dubious about the last two paragraphs, and would love to see cites. My dim recollection is that the primary core-temperature sensor in humans is in the brain, and of course basically tracks blood temperature. Cooling the skin or stomach isn’t going to directly affect that (And the core-temp monitor is not the same thing as the skin temperature sensations).

Body temp is regulated by the hypothalmus in the brain.

Hypothalamus

The hypothalamus functions as a type of thermostat for the body.[3] It sets a desired body temperature, and stimulates either heat production and retention to raise the blood temperature to a higher setting, or sweating and vasodilation to cool the blood to a lower temperature.

I’m having trouble turning up the level of detail in description of how the body temp sensors work. Apparently nerve cells in the skin and body sense temp and send that information to the hypthalmus, which then adjusts and regulates they body’s response through hormones.

[weak cite: “The hypothalmus contains not only the control mechanisms, but also the key temperature sensors.”] if that’s wrong, please correct me.

Saw that one, also saw this one
http://www.biologyreference.com/Ta-Va/Temperature-Regulation.html

Body temperature is regulated by a system of sensors and controllers across the body. The brain receives signals regarding body temperature from the nerves in the skin and the blood.

The and confused me a bit, but if I parse it right, it says temp signals from nerves in the skin, and from blood (not nerves in the skin and nerves in the blood).

http://optimalhealth.cia.com.au/homeo.html

The regulatory center for body temperature, located in the hypothalamus, is sensitive to temperature changes in arterial blood flowing through it.

Oooh, but pdf
http://www.biologymad.com/resources/A2%20Homeostasis.pdf

In humans, body temperature is controlled by the thermoregulatory centre in the hypothalmus. It receives input from two sets of thermoreceptors: receptors in the hypthalmus itself monitor the temperature of the blood as it passes through the brain (the core temperature), and receptors in the skin (especially on the trunk) monitor the external temperature. Both sets of information are needed so that the body can make appropriate adjustments.

Quercus said:

And I find it hard to believe that something cold in the stomach or on the skin is going to affect the hypothalamus,

Okay, so as pointed out, the skin has temp sensors that the hypothalmus uses to determine what it needs to do. The temp from the stomach is conveyed by the blood in the stomach wall getting cooled, and that cooling being conveyed through cool blood to the hypothalmus. So what is in question is how much a bowl of ice cream or a liter of ice water is going to cool the blood and thus affect “core temperature” readings.

Anyway, I suspect the reason you feel warmer a little while after a cool shower on a hot day isn’t because your body’s thermostat has malfunctioned, but rather because your skin is better at detecting relative differences than absolute. So after being in the cool shower, the outside air feels much hotter, even though it hasn’t gotten any warmer outside.

If you take a cold shower, you are dramatically cooling the body. This will trigger the hypothalmus that you need to conserve body temp, so it will trigger things like vasoconstriction, ATP release, etc. “Ramping up the metabolism” is a descriptor of the muscles becoming more active and trying to put out more heat. Then you step out of the shower and back to the hot air conditions, your body is trying to keep warm and is suddenly surrounded by heat, and has to adjust back the other way. The alternative is to use warm water - it cools by evaporation and convection, but is warm enough not to trigger the body to start heating but rather to keep cooling processes active. Ergo, you stay cooler.