Jun 20, 2005
Tea Cools You Down
At the time of writing, the UK was in the middle of a rare heatwave, and my mother, as usual, suffers when the mercury rises about 25 or so (it’s 33 here today!) and, as usual, is suggesting everyone has a nice cup of hot tea to help them cool down.
Of course, it is easy to mock the underlying physics of such a suggestion (Does Hot Tea Really Cool You Down?), and I have explained to my mother that it’s a myth, but such conventional wisdom seems to persist and someone only this morning visited the sciencebase site searching for an answer to the question, does hot tea cool you down? Or more generally “does a hot drink cool you down?” Someone, even asked the presumptuous question: “Why does drinking hot drinks cool you down?”
Bluntly, no.
However, even as a hot drink, it can make you feel refreshed even when the air is still and humid and as long as you don’t gulp it down too quickly it won’t make you even more sweaty. I guess there may be a psychological effect, if the air is warm and humid and you drink something hot, that will heat you up more and make you sweat, sweat evaporates from your skin cooling your skin, so maybe you end up feeling slightly cooler, but I’m still not convinced. In fact, sweating inflames the skin in some ways as capillaries open up and you actually feel hotter when you sweat more, unless you’ve got a very strong fan. Anyway, from the thermodynamics point of view adding a hot liquid to a cooler container (your body) will raise the temperature of the container.
Now, iced tea is a different matter – make mine a peach one! And, plenty of ice!
Of course, there’s also this well-known 19th century quotation from Gladstone
If you are cold, tea will warm you. If you are too heated, it will cool you. If you are depressed, it will cheer you. If you are excited, it will calm you.
For more on teatime etiquette, check out this item.
Doesn’t your body lose it’s heat trying to cool it down?
Mr/Ms “Cures Like” All I can say is “bullsht”. Like does not cure like. If you hit your thumb with a hammer, then hitting it again “a little bit will” not stop it hurting. Catch a virus and exposure to a little bit more virus will not cure you. Likewise warming something that is hot will not cause it to cool.
We do mention the idea that the hot tea causes the body’s temperature controls to kick in and because these are not perfect, they could overshoot the mark. But, I just ran up the stairs to my office and am not drinking a hot cup of tea, which has left me feeling slightly flushed, and certainly warmer inside than before.
Seeing as you’re such a stickler for the science, why not provide us with a reference or two for this legendary experiment? If it was carried out on a statistically significant cohort and shows actual temperatures of the subjects before and after hot and cold drinks…then we might be closer to being convinced.
Many years ago I remember this legend being put to the test by experiment, like every good scientist should do rather than pontificate without any direct knowledge.
The assertion that they tested was the one that stated that drinking a hot tea after exercising would cool you off faster than drinking a cold drink. So what they did was have a test subject exercise for some minutes and then drink a hot or cold drink and then record the results with a relatively new invention, the thermal imaging camera.
The thermal images clearly showed that the person who drank a hot tea after being hot from exercise was lowering his body temperatures faster than someone that drank a cold liquid after exercising. The principle that causes this is know as “Like cures like.” Where a specific condition is changed by administration of a similar condition. The heat of the tea informs the body that it is hot and the body response is to cool itself off.
I don’t think it has anything to do with the Chinese. My grandmother used to make the claim about a nice cup of tea. Ultimately, it’s about *when* you drink that cup of hot tea. It’s often after you’ve been running around the shops or slaving over a vacuum cleaner, you finally get to sit down kettled boiled, tea bag in the pot, and relax, it’s that that cools you down, the ritual of drinking the tea just enhances the relaxation effect by association. But, the physics tells the truth about the actual temperature differentials.
I’m guessing this whole “hot tea cools you down” thing comes from the Chinese concept that all foods either warm or cool the body. Some obvious warming foods are ginger and garlic. It may seem counter intuitive, but most black teas are believe to have cooling properties, even though they are served hot. Just as cold ginger ale is still a warming drink, because ginger itself warms the body.