When it’s really hot outside you might want to just to close the curtains and keep cool in front of the fan. But when you have no choice but to face the heat you might be hankering for a tall glass of cool water or a glass of Coca-Cola with ice. But, traditional wisdom from around the world maintains that drinking a hot drink on a hot day is actually the way to cool your body off. So what’s behind this custom and does it work?
If the thought of drinking a hot drink when it’s scorching outside makes you feel warm then you’re not wrong. As it turns out it can make you feel hotter, but if the humidity is low enough then your body can sweat more in response to the rise in internal temperature.
But, this aspect of the phenomenon isn’t an old wives’ tale. A 2012 study from the University of Ottawa’s School of Human Kinetics and researcher Ollie Jay showed that drinking different temperatures of liquids changed how the body processed heat. Participants in the study were given fluids of various temperatures and then asked to exercise. They were given drinks at a range of temperatures, the warmest being at 50˚C (that’s 122˚F). This is cooler than tea or coffee that’s just been made, but is still quite warm.
What researchers found was that during exercise in the lab on stationary bikes those who had consumed warm liquids were found to have a higher rate of evaporative sweat than those who drank cool drinks. Because of this they also stored less heat in their bodies.
The researchers theorized that this change in how the body sweats after drinking warm liquids is due to thermosensors that are found in the stomach and esophagus and which are sensitive to warm temperatures.
According to a Smithsonian interview with Jay, if it’s too humid then drinking hot drinks becomes counterproductive. Jay said that, “What we found is that when you ingest a hot drink, you actually have a disproportionate increase in the amount that you sweat” and continued by saying “…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 the added heat to the body from the fluid.”
Jay also added that if it’s too humid then drinking a hot drink will only make you feel hotter and you might want to stick to cool beverages instead.
To recap if it’s a hot day with low humidity (and you’re not wearing too many clothes to allow to sweat to evaporate properly) then drinking a warm drink can help you cool off by forcing you to sweat more. And, if it’s a hot day that’s also humid go ahead have yourself a cold drink instead.