Image courtesy of Olga Filonenko, Flickr
Perhaps you’ve heard of people from India or Bedouin tribes drinking hot tea to cool down. It sounds like one of those counterintuitive ideas that must be true because it’s so crazy. So is there truth behind the claim?
According to a study published by University of Ottawa’s School of Human Kinetics, hot fluids can cool you down under the right conditions. In this study, participants were given water at different temperatures. They found that those who drank hot water produced more sweat. If the sweat was able to evaporate fast enough, it more than made up for minor heat gain of drinking hot liquid. On the flip side, those who drank cold water actually sweat less, resulting in greater heat gain.
Now the big caveat is that the sweat has to evaporate. If you’re wearing too many clothes, or if you’re exercising too hard, or it’s too humid out, that sweat is going to stay on your skin and you’re actually not losing the heat gained from drinking a hot liquid. In these conditions, it’s better to drink cold fluids.
Another interesting point, it’s not necessarily the gain in body temperature of drinking warm fluids that causes you to sweat. It’s actually temperature sensors along your mouth, esophagus, and stomach that trigger sweating. So if you want to sweat less, try drinking iced tea.
Finally, you may have read other studies that claim the opposite. Ollie Jay, a researcher at University of Ottawa’s School of Human Kinetics found that previous studies were flawed in their method of recording core temperature. In these studies, a rectal thermometer was used (ouch). However, in the Ottawa study, subjects were monitored with 8 thermometers throughout the body, including one in the rectum and even down the esophagus! They found that cold water pooling in the stomach cooled the rectal thermometer, but not the rest of the body.
Just remember, if the sweat isn’t pooling on your body, try drinking hot tea, it might cool you down more! Otherwise, stick to a nice iced tea for that soothing feeling.
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Sources:
A hot drink cools you faster than a cold one – myth or reality? The Globe and Mail
Body heat storage during physical activity is lower with hot fluid ingestion under conditions that permit full evaporation. Acta Physiol (Oxf). 2012 Oct;206(2):98-108. doi: 10.1111/j.1748-1716.2012.02452.x. Epub 2012 Jun 9.