Does drinking tea on a hot day cool you down? written 10 years ago

Cup of tea

Summary

Using a simple model it is easy to come to the conclusion that drinking a hot cup of tea on a warm day will not cause any beneficial cooling. The human body however is a complicated machine, and using a more refined model we can show that although one specific part of the body may heat up, the majority of the body will cool down — below 37°c.

Introduction

“have a cup of tea, it’ll cool you down”

The first time I heard this was a million years ago at one of my primary school’s sports days. All the kids were getting small cups of incredibly sugar filled orange juice¹, whilst the teachers and parents were drinking cups of tea. I quizzed a random teacher about this apparent fallacy and was told that drinking a hot drink cools you down more than a cold one.

Leaving this statement unquestioned until my more senior years I began to ask colleagues and friends if they had heard of the same mystical properties of hot tea as I had all those years ago. All of them had heard this at some point, some questioned it, some were firm believers and some others thought it quite absurd.

The UK Tea Council even promotes this magical property of tea!

I therefore sat myself down and set myself the challenge of finding out once and for all the answer to the question:

Does drinking tea on a hot day cool you down?

Theory

  1. Hot drinks cause your body to sweat, and by sweating it causes your body to cool down;

Assumptions

When we make these two points, the proof we need to answer our question is quite simple…

Proof that drinking hot tea does not cool you down on a hot day

  1. As stated above the body sweats if and only if the temperature of the body is above 37°.

  2. Once the hot drink has been consumed, the internal temperature will rise (above 37°), and sweating will begin.

  3. As the person sweats, the temperature will be reduced, until it is at 37°.

  4. At 37°, sweating will stop.

  5. The temperature of the person will remain at this temperature.

The key point is that if you’re not already sweating, then your body is doing a good job of keeping you cool without needing to sweat — the energy being created inside you is being dispersed adequately by convection. Adding heat to your body in the form of tea worsens the situation, and forces the body to remove the new heat by sweating. Your body is clever however, and will only sweat enough to remove the additional heat added by the tea, and won’t just start sweating indefinitely².

Conclusion

Drinking a hot drink on a hot day is not going to cool you down. It will make you warmer for a while, then you’ll return to your normal 37°.

Further Investigations

For the proof above we’ve taken quite a simple model of the human body — Assuming that the heat from the tea is dispersed all over the body. In reality though, the heat will be localised to the body’s core — the important bit. The brain worries quite a lot if the core of the body gets too warm, and so, what if under this situation the brain goes nuts and demands that everyone sweats until the core is back at a proper temperature? This might just cause a net temperature loss throughout the entire body.

To explore this option, I invented some random guesstimates and came up with a new model with some more complexity:

Facts and Figures

Amount of tea250ml
Specific Heat capacity4.186
Tea temperature60°c
Body Temperature37°c
Net Temperature Gain23°c
Total Energy (heat) in tea24069.5cal
Water loss per hour1 litre
heat loss per gram of water580cal/gm
Heat loss per minute9666cal
Core Body Weight10kg
Entire Body Weight80kg
Specific Heat capacity3.5(guess)
1 cal raises CORE body heat by0.0000286°c
1 cal raises ENTIRE body heat by0.0000036°c

The facts and figures depicted here are based on best guesses and although they won’t be too far off, they shouldn’t be used for proving things³.

The values have been used to create the graph pictures below.



In this model we assume that the “core” (10kg) of the human gets all of the heat from the tea, and thus in the example given above will raise in temperature by 0.68°c. (Not much, but enough to get the body worried). This then causes the body to go into sweating mode, pumping 1l of water to the skin every hour. Assuming all of this gets evaporated, this will consume 9666 calories of body heat every minute.

This is where we differ from the above example though. Although only the “core” of the body is at a heightened temperature, the only way to dissipate this heat is to cool off the entire body, meaning that the 9666 calories of heat are removed from the entire body, and not just the core (since it’s hidden within 4 inches of blubber). This means that 0.0000036°c is removed from the entire body (including the core) every minute. Thus, since the majority of the body was already at a reasonable temperature, it will actually start to feel cooler, as it will have dropped below it’s optimum 37°c.

Body/Core temperature After drinking a hot cup of tea on a Sunny day. Showing that as the core cools off to 37 degrees, the majority of the body is at 36.4 degrees.
Body/Core temperature After drinking a hot cup of tea on a Sunny day

Conclusion 2

So, assuming that the above assumptions are correct, it seems that there might be a shred of truth to the tale that drinking a hot drink will cool you down on a warm day.

Links


¹ The kind of orange juice that can only be served at schools, from gigantic beaten up aluminium jugs.

² This is a Good Thing, since you would probably die of dehydration otherwise.

³ Read into this what you will.

← previous entry | next entry → Sun 26th Aug 2007 - 17:13 | 17 comments | tagged with Random, Essays

 Comments 17 comments made

Ah ha! So using your logic I was right when I mentioned this before!

I am very impressed by your level of boredness to research this on the only sunny weekend of the year.

Paul’s GravatarPaul 0 day later

Very scientific! Whilst I remain sceptical, my Mum’s a biology teacher and she seems to agree with your second conclusion.

PS:
<css-pedantry>
Your “facts and figures” box renders wrongly in Firefox due to a lack of non-floating content within it…
</css-pedantry>

originally posted by Paul

Your “facts and figures” box renders wrongly in Firefox due to a lack of non-floating content within it…

How do you mean renders wrongly? Looks fine to me.

Rob 0 day later

And for god’s sake, the relative dates code is broken again.

Paul’s GravatarPaul 0 day later

originally posted by Rob

How do you mean renders wrongly? Looks fine to me.

Hmm it did have the blue box contracting to not contain the the tables when I looked earlier, but I’ve just refreshed and it looks fine now. Odd… but never mind.

originally posted by Rob

And for god’s sake, the relative dates code is broken again.

Ha ha!

originally posted by Paul

Hmm it did have the blue box contracting to not contain the the tables when I looked earlier, but I’ve just refreshed and it looks fine now. Odd… but never mind.

Yeah I realised I had made some changes to the stylesheet to fix just this. It was probably just cached…

Angela’s GravatarAngela 0 day later

As a biologist and also a great tea - drinker, I’d like to agree with your second conclusion. Your first assumption is I’m afraid biologically flawed in that it’s too simplistic. However your second line of reasoning is much closer to what actually happens, with the hypothalamus region of the brain continually monitoring blood temperature, and making adjustments as necessary, to maintain a constant body temp. It’s true that hot tea causes blood temp to rise in the core of the body, and the hypothalamus puts corrective actions into place - like increasing sweat production, to bring body temp down. It really does work - as anyone who is a tea drinker will tell you! It doesn’t work so well with other hot liquids - that’s the magic of tea!!

originally posted by Angela

It doesn’t work so well with other hot liquids - that’s the magic of tea!!

Thanks Angela, it’s good to have the opinion of a real Scientist, rather than the mumbo jumbo I spiel out!

I do however think the only true way to resolve this is a large group of people taking a trip to a beach, and a very big tea urn :)

originally posted by Rob

I do however think the only true way to resolve this is a large group of people taking a trip to a beach, and a very big tea urn :)

I volunteer!! And I’ll be drinking tea no matter what the weather, I am a devoted DIsciple of the Gaffer :D

Antoxa Gray Ocheviduous Guy’s GravatarAntoxa Gray Ocheviduous Guy 2 years later

Well, I just drink 2 cups of hot tea, and then found your article. Actually feel better. I didn’t knew about that myth, I just like tea, and don’t have cold liquid right now. That’s why I drink tea.

jensen’s Gravatarjensen 2 years later

anyone that thinks a HOT liquid on a HOT day will cool you down should give your head a shake, NOT TRUE, retards

Calum Matheson’s GravatarCalum Matheson 3 years later

Cheers Rob - I really enjoyed reading this article. I say article, as I’m sure I’m sure it took significantly more effort to produce than the average blog post.

You must thank your dodgy blog software for bringing it to my attention. I clicked as it said it was posted 0 days ago. Seems the truth is closer to 3 years!! :)

Paul T’s GravatarPaul T 3 years later

Brilliant! Humourous and logical too. A good read.

osman torlak’s Gravatarosman torlak 3 years later

way a.q. harbi çay insanın harareti alıyormuş … Allah sizi top etsin emi üşenmeden araştırmışlar.

Mimi’s GravatarMimi 4 years later

Riiiiight, and a freezing milkshake on a freezing day will warm me up.

Alan Budge’s GravatarAlan Budge 4 years later

I feel that your theories are flawed in many ways. But before we get onto that, I would like to know a couple of things. First of all I would like to know what type of seat you were sitting in when you sat yourself down? This is a very important question and one which should be answered in full detail as sitting in an uncomfortable seat could alter the results of your investigations. Secondly, I would like to know what words you muttered to yourself before sitting YOURSELF down. Onto the main points - Where did you get your assumptions from? You can’t just assume that the body sweats at 37 degrees. This is a disgusting assumptions. Its both narrow minded and naïve. As EVERYBODY knows everybodies body is there bodies body and nobodies body but there’s. I will simplify this for you, everybodies body reacts differently to heat. Therefore, somebody who sweats at 37 degrees may not be the same as someone who sweats at 37.5 degrees. To summarise and conclude - tea does cool you down and it tastes swell.

Jenni4’s GravatarJenni4 4 years later

It doesn’t matter to me what experiments tell you. When I’m hot, I feel MUCH more comfortable when I drink cold water than drinking hot tea. That’s all I care about.

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