The current heatwave in England has had countless old wives, and a few elderly husbands, calling for a nice cup of tea to cool them down. And, when I say tea, I’m not talking none of that chilled variety that comes in peach and lemon and all sorts of other gawdy flavours, I mean a nice cup pored from a cosy-covered pot, with a splash of semi-skimmed milk and a couple of lumps of sugar (ten if you’re a builder or plumber, of course). So, what’s going on? Why drink a hot drink when it’s hot and you want to cool down.
Physically, it’s an illogical thing to do, Captain. Add something hot to a body at a lower temperature and the cooler body will absorb heat energy from that hot something and its temperature will rise, surely?
Physiologically, things might not be so clear-cut. Drink a hot drink, and yes, the temperature of your stomach’s contents will rise, but this will also cause a slight hastening of the heart, expanding blood vessels across the skin, and an increase in sweating as the brain switches on the various feedback-controlled temperature regulators.
It’s that word “feedback” that provides a possible clue as to why a cup of hot tea might have gained its reputation among English old wives as a good coolant. Feedback loops always have a time delay. So, the instant burst of heat that comes from sipping on a nice cup of tea will inevitably bring you out in a bit of a sweat, raise your heart rate etc, but those compensatory measures take time to be reversed, possibly more time than it takes for the contents of your gut to reach “body temperature” again. So, their cooling effect may just last a little longer than is actually needed to get you back to normal temperature and so you may end up a little cooler than when you started.
All that said, I don’t think our temperature feedback systems are that tardy. The real reason that old wives perceive a hot cup of tea to have a cooling effect is probably more to do with interrupting whatever activity it was that made them hot in the first place, partaking of the cup-of-tea creation ceremony, and sitting down in a darkened room with their feet up to drink it.
I could be wrong, and now that the storms are on their way this atypical English weather is likely to be replaced with the more usual wet and grey with which visitors become so familiar.
Now, where did I put those teabags…?