At 06:46 PM 1/4/01 EST, you wrote:
>The International Meteor Org states on their website
><http://www.imodot net/visual/major01.html>
>"do not have hot drinks -- they dilute the blood vessels and make you feel
>colder"
>
>This is really true? Everyone that I've ever observed with has always
>advacated "Drink some hot chocolate, or do you want something hot to drink?"
>
Reading this thread I was struck by the lack of any quantitative estimates
of the benefits of hot drinks.
assuming you drink a large mug of hot coffee. How much heat are you going to
absorb.
The temperature of the coffee as it is consumed. Not brewing or in Thermos
temperature.
Probably around 70 degrees centigrade would be a reasonable estimate for
sippable hot drinks. However tea at 55 degree centigrade was about as hot as
I could comfortably drink fast. With slow consumption continuous body heat
loss will mask any effects.
Assuming about 500 ml, nearly a pint, is drunk quickly the calories of heat
input is 500 X the temperature difference tea and body temperature 18
degrees. Obviously this is a variable if you drink hotter drinks the heat
imput goes up.
500 X 18 = 9000 calories or 9
kilocalories ( the calories of diets etc.)
Assuming an 80 kilogramme person
transient rise in body temperature = 9/80 degrees centigrade
= 0.1 degrees.
The energy input to the body from this large amount of hot drink is less
than you would get from eating a square from a chocolate bar. I vaguely
recall a figure of 200 Calories for the energy input from a Mars bar.
So all you get from the hot drink is a short lived but comforting feeling of
warmth but the actual heat taken in will be rapidly dissipated. For the
longer term the sugar you have in the coffee will be far more important.
The actual physiology though is more complex as if you raise your core body
temperature too much the body will react by dilating peripheral blood
vessels to dissipate excess heat and lower the core temperature. The extra
flow of cool blood will probably offset the heat gain from the drink. If
this does not happen a small increase in core temperature may produce a
small increase in metabolic rate and therefore heat generation. This ignores
an pharmacological effects from caffeine etc in the drink.
Probably you would best to regard the drink as a way of supplying fluids
without chilling the body. The feeling of warmth is a bonus rather than a
physiologicaly important benefit.
Nick
Nick Martin, Bonnyton House, By Ayr, Ayrshire KA6 7EW ,Scotland, UK.
Latitude 55 24'56" Longitude 4 26' 00".
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