While conventional wisdom says a cold drink will help cool the body, research now suggests that hot beverages are the way to go.
According to University of Cambridge neuroscientist Peter McNaughton, there are nerves in the tongue and mouth that have special molecules in them called receptors. As the name suggests, these receptors receive signals from the world outside the nerve.
There are all sorts of receptors in all sorts of nerves, but the nerves in the tongue have a lot of one particular receptor that responds to heat, so when you eat or drink something hot, these receptors get that heat signal and that tells the nerve to let the brain know what’s going on.
When the brain gets the message “It’s hot in here,” it turns on the mechanism we have to cool ourselves off: sweating.
“The hot drink somehow has an effect on your systemic cooling mechanisms, which exceeds its actual effect in terms of heating your body,” McNaughton said.
Ollie Jay, a researcher at University of Ottawa’s School of Human Kinetics also found truth in the counterintuitive cooling technique after conducting a study that was released earlier this year.
“What we found is that when you ingest a hot drink, you actually have a disproportionate increase in the amount that you sweat,” Jay says. “Yes, the hot drink is hotter than your body temperature, so you are adding heat to the body, but the amount that you increase your sweating by—if that can all evaporate—more than compensates for the added heat to the body from the fluid.”
The increased rate of perspiration is 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, he adds that the catch is that the extra sweat produced as a result of the hot drink actually has to evaporate for it to have a cooling effect.
“On a very hot and humid day, if you’re wearing a lot of clothing, or if you’re having so much sweat that it starts to drip on the ground and doesn’t evaporate from the skin’s surface, then drinking a hot drink is a bad thing,” Jay said. “The hot drink still does add a little heat to the body, so if the sweat’s not going to assist in evaporation, go for a cold drink.”