A cup of hot tea does not cool you down

nice-cup-of-teaAt 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.

14 thoughts on “A cup of hot tea does not cool you down

  1. I think the “hot tea cooling you down” is a particularly English myth. One might imagine a bustling person heading home after an active and hot day shopping. First thing they do on entering theor home and putting down their bags is to “pop the kettle on ” for a “nice cuppa”. By the time the kettle has boiled (obviously, it’s the water in the kettle) their heart rate and sweating have already subsided a little. Sitting down to drink their cuppa then enhances that effect. However, thermodynamically adding a small volume of liquid at 50-60 Celsius to the contents of the stomach does not reduce body temperature. I think it’s purely the psychological effects of relaxation…

  2. A quick look at PubMed (in response to a conversation overheard on twitter that ice cream in winter will warm you and hot tea will cool you) gave very little indication that a hot drink will cool you faster. In fact, at least one exercise physiology study indicated that cold drinks improve performance in athletes (and isn’t that what we are looking for?). “Cold drink ingestion improves exercise endurance capacity in the heat” http://www.ncbi.nlm.nih.gov/pubmed/18685527 Not sure how the hot tea works with South American soccer players given that study. (A review of similar studies was somewhat inconclusive. None of the included studies showed increase performance and cooling with a hot drink, they just questioned whether the cool drink was a significant factor as the first study indicated).

    I found a study titled “Skin temperatures during sunbathing and some observations on the effect of hot and cold drinks on these temperatures [proceedings”] from 1977.
    http://jp.physoc.org/content/267/supplement/1P.full.pdf
    This study did seem to indicate a decrease in skin temperature after the hot drink but not the cold.
    However, there is a significant problem with this study: they used ONE subject.
    This study cannot possibly stand with such a low sample size. Without further peer reviewed studies, I expect most of the evidence is anecdotal and I would go with hydrating yourself in a way that feels most comfortable and refreshing assuming you are not suffering heatstroke or hypothermia, in which cases there are prescribed first aid treatments that should be followed.

    And yay for you, David, for liking peach iced tea, too! It’s my favorite!

  3. @Ryan Science, you say? Is that the same sport that consults psychics and homeopaths? More money does not equate to more brains, just look at the state of the world economy.

    Yes, drinking something hot will make you sweat, especially if you’re overheated already, but sweating is not 100% efficient and the fundamental physics means that it cannot offset the rise in stomach temperature caused by pouring in what you describe as a “steaming hot tea”.

  4. I’m sorry, but I have to be the voice of reason here: Hot tea does cool you down. It’s not an instant fix-all remedy, but it does. It opens your pores.

    If it didn’t, why then do they give soccer players in South American, African and Middle Eastern countries steaming hot tea at half time? It’s not because of the culture (well maybe partly), but because it cools you down. Do you really think the biggest sport on earth, with more money, science and etc invested into it than most other things in life, would be doing this if it didn’t help? I will take it from professional sports scientists and doctors, thank you very much (speaking to you, David Bradley), rather than trust some pseudo-physician online.

  5. 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.

  6. 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.

  7. 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.

  8. 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.

  9. It’s not a closed system.

    Sweating has done it’s job, as have other physiological functions to expose the body’s heat to the environment where it will radiate away more efficiently and continue to do so – because it’s not a closed system.

    The same conclusions are to be drawn from experiments in extreme cold. Those with wet skin (either from sweat or falling into icy water for example) will lose body heat, far faster than the same person with dry skin.

  10. Anon, yes sweating does cool you down. But, there is a limit and wrt to the whole “tea cooling” issue, you still haven’t accounted for the fact that you’re adding heat to the system…

  11. Sweating cools you down, as water against the skin, which radiates heat away from the body, 20 times more quickly than if it were dry. It is particularly cooling in front of a fan for the same reason.

    This is one of the reasons why it is better to take off wet clothes in extreme cold. You’ll survive longer with no clothes!

  12. Yes, sweating does cool you down. But, it’s not 100% efficient and adding a volume of hot liquid to a system with such an evaporative cooling system will cause the temperature of the system to rise regardless. Moreover, as the level of sweating rises it becomes more and more inefficient at cooling you down if there is no effective way to allow the sweat to evaporate.

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