It may sound counter intuitive but in many countries around the world, conventional wisdom says that you can cool down on a hot day by having a hot drink. When the weather is hot in Turkey, the hot drink believed to cool you down is, of course, a glass of black tea.
There have been several scientific research projects on this subject that make interesting reading but even then the answer is not so clear-cut.
Briefly, some say that a hot drink can cool you down, but only in specific circumstances, while others say this is nothing more than wishing thinking and several variables must also be taken into account.
If the assumption that tea can be cooling is correct, how did the idea first originate?
If a glass or mug of tea cools down the drinker this is said to be because it lowers the amount of heat stored inside your body by causing perspiration.
Researchers found is that when a hot drink is consumed, there is a significant increase in perspiration.
This is because the hot drink is hotter than the body’s temperature, thereby adding heat to the body.
But the amount of increased sweating —assuming it can all evaporate — more than compensates for the added heat to the body from the fluid.
The ‘hot drink’ theory was tested on cyclists in laboratory conditions. Each cyclist was equipped with skin temperature sensors and a mouthpiece measuring the amount of oxygen consumed and carbon dioxide produced, which indicated the amount of heat produced by the body’s metabolism.
The researchers also carefully tracked the air temperature and humidity, among other factors.
The data yielded an overall picture of how much heat each cyclist produced and how much each released to the environment, and those drinking hot water (roughly 50°C) stored less heat in their bodies than the others.
Hot drinks lead the body to produce more sweat, but many scientists now reject the common belief that the hot drinks raises the body’s core temperature.
Instead they think is that it’s thermosensors that line the throat and mouth that elicit the additional sweating response.
Whatever the case, the increased rate of perspiration appears to be the key.
Although sweat may seem like a nuisance, the body perspires for a very good reason. When sweat evaporates from the skin, energy is absorbed into the air as part of the reaction, thereby cooling the body.
A larger amount of sweat means more cooling, which more than counteracts the small amount of heat contained in a hot beverage relative to the entire body.
However, the sceptics only believe that this theory works in very specific circumstances: a hot, dry day, where you’re not wearing so many clothes that the sweat is prevented from easily evaporating.
In other words, if it’s hot and you’re in a dry desert, a cup of hot tea might actually be the trick to help cool you down.
But if the location is humid, hot tea may not have the desired effect, especially if your body is covered with too many layers of clothes, reducing the ability of the sweat the body produces to evaporate.
Another reason given is that when you drink a hot cuppa or eat spicy food like curry or chillies, it triggers the central nervous system, causing heat in the mouth that will cause the skin temperature to increase resulting in vasodilation [a dilating of the blood vessels] and sweating.
This in turn will move the heat away from the body to the skin and then to the air surrounding the body.
For people living in cooler parts of the world, opting for a cool refreshing drink on a hot day or eating ice cream can cause blood vessels to tighten, making you feel much hotter, rather than cooler.
Some scientists reject the ‘hot/cold drink’ hypotheses completely, saying that although hot tea will make you sweat more, and increase your cooling, the extra cooling won’t be enough to offset the heating-up from the tea.
In the end, all of this advice comes with a warning: not drinking enough fluids (and this doesn’t include beer or wine) can cause dehydration, which has very dangerous consequences if not remedied.
Doctors say that by the time you feel thirsty, you are already dehydrated. So just keep drinking water and forget the tea or other drinks.
It contains no calories and is great for your health in other ways.
Having said that, there is still a fierce medical debate about what constitutes enough water.