This article was first published in The Skeptical Inquirer.
Nothing pairs better with hot summer weather than an ice-cold drink, right? Well, as the old saying goes, a hot drink on a hot day will cool you down faster.
It might seem counterintuitive to drink a hot drink when you’re already feeling overheated, but recent studies have shown why this favorite advice of my nana is actually scientifically sound.
Dr. Ollie Jay, a researcher at the University of Ottawa, tested this concept in the laboratory. First, his team set up cyclists with skin temperature sensors and a mouthpiece to measure O2 and CO2. Then, while keeping the temperature and humidity in the lab constant, they had the cyclists consume either hot or cold drinks while cycling. Their data showed that those drinking hot water (roughly 122 degrees F) stored less heat in their bodies than the others.
However, there is a critical caveat to this finding and it has to do with how our bodies dissipate heat: by sweating. As Jay put it, “If you drink a hot drink, it does result in a lower amount of heat stored inside your body, provided the additional sweat produced when you drink the hot drink can evaporate.” So, if you are in a highly humid environment, say a sauna or a rain forest, or submerged in water, where your sweat already can’t evaporate well, an increase in your sweating rate won’t have a cooling effect. Under these circumstances, drinking a hot drink will not help you cool down. But, in dry heat conditions, the ones we mostly encounter, a hot cup of tea will indeed have better long-term cooling effects than a glass of iced tea. For me, however, nothing will ever beat an ice-cold Stella Artois on a hot summer day.
