A few years ago I woke up drenched in sweat in a small riverine village in the Brazilian Amazon. My guide handed me a plastic cup of steaming hot acai porridge. At about 8 in the morning, it was already over 90 degrees outside, but she urged me to drink it. “It will give you strength and cool you down,” she said. I was skeptical–but she might have been on to something.
Back in 2012, a guy named Ollie Jay was studying the way the body stores and distributes heat at the University of Ottawa. Jay and some colleagues put people on exercise bikes, got them good and sweaty, then measured their body temperatures after giving each participant a drink of water. Some folks got cool water, some people got warm water. Initially, the body temperatures of the people who drank the warm water went up, as you might expect, but after everyone had time to sit around and dry off, they found the warm water drinkers had actually stored less body heat than their cool water counterparts. How’d they do it? Through their sweat.
Sweat is your body’s natural response to heat. Collectively, all those little droplets are just energy, or heat, leaving your body. In a nice, dry climate, that excess energy evaporates off your skin and leaves you a little bit cooler. The evaporation is the most important part–in Jay’s study, the authors noted that they only saw body heat storage decrease when their test subjects were “under conditions permitting full sweat evaporation.” In other words, a room with plenty of ventilation and very little humidity. When you consume something hot, it warms up your esophagus and stomach, which then triggers your body to start sweating in order to release some of that heat. Under the right conditions, the more you sweat, the more heat you’re purging from your body.
So the next time someone hands you a steaming cup of something in the midst of an Indian summer, take it. As luck would have it, you really can fight fire with fire. Well, sorta.