Will Hot Drinks Keep You Cool on Hot Days?
With temperatures reaching record highs not only here in the South but throughout the U.S. and around the world, we're all thinking about ways to keep our cool this summer. One idea that's been floating around for decades is that sipping hot drinks in hot temperatures will cool our bodies off. But will it? We checked in with experts to find out.
Will Hot Drinks Keep You Cool?
When asked if there is any science behind the belief that drinking hot drinks in hotter weather helps manage body heat, Douglas J. Casa, Ph.D., CEO of the Korey Stringer Institute and a professor in the department of kinesiology at the University of Connecticut, told Southern Living, "[There is ] absolutely no evidence. To be very clear, hot drinks are a very bad idea during hot weather. They will cause you to heat up even more than you already are.
"It is very beneficial to have cold drinks to cool yourself down from the inside," Casa continued. "Some good evidence is the benefit of slushie-type drinks to help keep body temperature down."
W. Larry Kenney, Ph.D., a professor of physiology and kinesiology at Pennsylvania State University and a member of the American Physiological Society, added "I can tell you that there is zero evidence that hot drinks are useful in warm weather. [It's an] old wives' tale."
Dry Versus Humid Heat May Make A Difference
Whether or not hot beverages can make a difference in managing body heat may depend on whether conditions are dry or humid.
S. Tony Wolf, Ph.D., a member of the American Physiological Society, says that there is some evidence that drinking a warm beverage increases evaporative heat loss potential and, therefore, reduces body heat storage in dry environments that allow for sweat evaporation. The key words here are dry environments. Think: desert conditions.
"The reason for this is that there are warm-sensitive thermosensors in the esophagus and the stomach, and when those sensors detect a rise in temperature, sweat rate increases," explains Wolf. "So, for those who are trying to stay cool in a hot-dry environment, drinking hot beverages may promote enhanced body heat dissipation." In other words, sweat.
"However, in more humid environments, where evaporation of sweat is limited, those increases in sweat rate are not likely to be as beneficial because the sweat is not readily evaporated into the environment," Wolf adds. "Evaporation of sweat is required for the dissipation of heat; if the sweat is not evaporated, it has no beneficial effect on the maintenance of heat balance. Thus, in humid environments a cold beverage is likely more beneficial than a warm beverage."
Nathan Morris, assistant professor in thermal physiology in the Department of Human Physiology and Nutrition at the University of Colorado, Colorado Springs adds, "In humid conditions, like in Florida, people often can't evaporate all the sweat off their skin due to the humid conditions, and it is the evaporation of sweat, not the production of sweat, that cools people down. More sweat dripping off their bodies won't cool them down more, so hot drinks in Florida will be particularly ineffective."
Morris adds that instead of hot beverages, "Fans are effective in humid environments because they help evaporate more sweat."
Whatever you decide to drink in the heat of the summer, one thing remains important: Stay hydrated.
"It is, indeed, important to replenish lost fluids in the heat to prevent significant dehydration," says Wolf. "In fact, the increased sweating associated with hot beverage ingestion likely increases the rate of dehydration; thus, more fluid intake would be necessary to replace the fluids lost through sweat."
Morris advises, "Since the body adjusts its sweat rate to account for the heat content of the drinks, people are best off drinking the temperature of water that tastes best and feels best to them, usually around 10-12°C (50-54°F), as it will encourage them to drink more water."
"If rehydration is key, then fluid temps between 50°F and 59°F are optimal to allow larger quantities of ingestion," says Casa, adding that warm drinks are not palatable for large volumes, and really cold liquids are hard to ingest in large quantities.
This is not to say that cups of coffee or tea, or other hot drinks, need to be completely off the table when summer temperatures are soaring.
"Drinking hot drinks are fine in hot weather if you are not going to have any intense challenges to your thermoregulation, for example exercising or working in the heat, or living in oppressive conditions, like without air conditioning," says Casa, adding that some athletes lose two to three liters per hour of intense activity in the heat.
"But, if you are going to be active or having to live extensively in the heat, stick with cold beverages," he advises.