Over the past few weeks, we've talked a lot about iced coffee. It is, after all, summer here in the Northern Hemisphere. Iced coffee seems like a natural way to help you cool down on a hot summer day. There's always been a contingent of coffee lovers, though, who insist that hot coffee is actually a better choice to bring down your body temperature. Now, new research seems to explain exactly why hot coffee may be a better choice for cooling you down than an iced drink. NY Mag's Science of Us column had a chat with Anthony Bain, an expert in heart, lung and vascular health at the University of British Columbia to find out exactly how hot coffee cools you down.
How Hot Coffee Cools You Off
According to Bain - who is paraphrasing existing research into body temperature regulation - the body figures out whether your hot or cold by listening to a network of sensors located in central parts of the body. When those sensors get hot, they send a signal to the hypothalumus, which then initiates sweating. As sweat evaporates on the skin, body temperature comes down. A large part of this thermo-sensing network is located in the gastrointestinal tract, including the esophagus and the stomach.
When you drink something hot, the sensors in your stomach go into overdrive and send out an SOS to the hypothalamus. The hypothalamus reacts by telling your body to sweat. The heat you lose through sweating and evaporation is greater than the heat you take in by drinking hot coffee. Thus, as counter-intuitive as it seems, drinking hot coffee can cool you off.
When to Ice It
But wait, there's more. Sometimes, iced coffee is a better choice to chill you out. Sweating only cools you off if it evaporates on your skin. If you're already hot and sweaty, more sweat won't cool you off - it just drips off of you and leaves you feeling icky. Likewise, if it's so humid that your sweat isn't evaporating, hot coffee will just add to the problem.
Bottom line: if you're not already sweating a lot, the air is mostly dry and you're wearing loose clothing that lets sweat evaporate, drink your coffee hot to cool you off. If you're already hot and sweaty, though, pour your java over ice and chill out.