Re: (re-submitted) Does drinking a hot beverage cool down body temperature?

Peter, 

In theory drinking a hot beverage might cool you down, but some cool water 
and a fan would do a much better job.

Your body seeks to maintain a constant core temperature (you can think of 
this as the temperture of your internal organs) of about 37.5 degrees 
Celsius. Temperature receptors are located throughout the body, in the 
skin, organs, and spinal cord. Other temperature receptors are found in the 
brain, in the anterior hypothalamus. The hypothalamus in large part 
coordinates the responses to temperature changes.

When your core temperature rises, the change is sensed by the hypothalamus. 
In response, your skin blood vessels dialate, and you begin to sweat. The 
output of your heart also increases to keep your blood pressure from 
falling.

The warm blood at your skin surface can give up its heat to your 
immediate surroundings, depending on the conditions. If its not too hot, 
you radiate more heat into the environment than you absorb, and so get 
cooler. You can also lose heat through conduction if you come in contact 
with something cold (for example, a tile floor), and through convection (if 
there is a little wind or you are moving around a bit). Most of the heat, 
however, is lost through evaporation of sweat. In fact, as the air 
temperture approaches body temperature, nearly all heat loss is through 
evaporative cooling.

So, how could a hot drink make cool you off? Well, theoretically, a hot 
drink could raise your core temperature beyond the level the environmental 
temperature would raise it. This would indicate to your hypothalamus that 
you are hotter than you actually are, and cause a stronger than normal 
response (stronger blood vessel dialation, more sweating). This line of 
reasoning predicts that drinking the drink would make you feel hot 
initially, but would cool you down more later. I haven't done this 
experiment myself, so I don't know if this actually happens. If it did 
work, I suspect the extra cooling effect would be brief.

In practice, drinking hot drinks to cool off doesn't seem a very smart idea 
to me. First, the MOST important thing you can do to maintain proper body 
temperature in hot conditions is to stay hydrated. Sweating is the most 
efficient cooling mechanism we have, and it uses up a lot of water. 
However, most hot drinks are things like coffee and tea, and caffeine acts 
to dehydrate you. Alcohol does the same, so no hot toddies. I suppose you 
could drink hot water, but why would you want to?

Secondly, it is not good practice to deliberately cause your body systems 
to overwork themselves. Overtaxing your temperture regulation system could 
have serious effects, particularly if you are not well hydrated, the 
conditions are extreme, you are overweight or in inadequate cardiovascular 
condition, or not acclimated to hot weather.

So, my advice would be to skip the hot water cocktail, and find some shade, 
a fan, and a glass of nice, cool lemonade the when you feel the heat.