What fluids should you drink when it's hot?

Hot or cold?

Also in this week's column:

What fluids should you drink when it's hot?

Asked by Andrew Wiseman of Cambridge, United Kingdom

The claim is that drinking a cold drink is better as the cold drink comes in contact with the tissues of the mouth, tongue, and throat thus soothing us, and it brings body temperature down since the body must warm up the drink to body temperature.

On the other hand, some say drinking a hot drink is better as the body has to use more energy to reduce the temperature of the drink to body temperature.

But this is contradicted by those who maintain that this body process only makes you hotter. People choose with their feet on this one (well, their mouths too).

People prefer cool drinks much more often than hot drinks during hot weather for sensory reasons rather than body temperature reasons. The same is true with hot drinks being more preferable during cold weather.

In fact, the temperature of the drink does not really matter unless a massive amount of liquid is being consumed or if the temperature of the liquid is extremely cold or extremely hot. If extremely cold, such an amount would probably make you sick and cause you to vomit and cramp. If extremely hot, it would burn your mouth.

The fact that fluid temperature, cooler or warmer, doesn't much matter is due to the much greater mass of the body compared to the drink. Cold or hot, the temperature of the drink is transformed to body temperature without much of a lowering of body temperature at all. The body's system of temperature regulation (homeostasis) is not so easily fooled.

The US Centres for Disease Control and Prevention in Atlanta stresses that during hot weather more fluids should be consumed. The CDC makes no recommendation as to the temperature of this fluid other than to "avoid very cold drinks" as these can cause stomach cramps.

The CDC says that besides water, salts, and minerals also need to be replaced in order to avoid heatstroke. It recommends avoiding caffeine, alcohol, and drinks with large amounts of sugar as these can "actually cause you to lose more body fluid".

Stephen Juan, Ph.D. is an anthropologist at the University of Sydney. Email your Odd Body questions to s.juan@edfac.usyd.edu.au

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