With a “heat dome” entering the national vocabulary, and predicted higher-than-normal temperatures in every state for the next three months, how can a person stay comfortable — and even more important, stay safe? Here are four tricks you may have read about — and what the science says about whether, and how, they work.
1. The trouble with tea
Travel to some warm, arid countries and you might come across a curious habit: drinking hot tea on blistering days to cool down. In 2012, it looked like this cross-cultural mystery might have been solved when a study suggested that drinking hot liquids in dry environments could drop core temperatures by triggering more sweating, our body’s built-in cooling system. But in 2015 another study challenged the results, concluding that, yes, hot beverages make us sweat more, but only to compensate for the extra heat we added to our body.
They concluded that the temperature of fluids consumed doesn’t make a difference in core body temperature, assuming that sweat can fully evaporate — a finding that the authors of the original study ended up supporting. But movement of dry air is important for sweat to evaporate, so in sticky heat, it might be best to stick to cold water.
2. Fretting over fans
Not all of us are lucky enough to have air conditioning in our homes, but at least we have fans, right? Turns out, the effectiveness of using fans during heatwaves is under debate. The question is, does circulating toasty air do any good?
Some studies have found that fans cause more harm than good by making a person more susceptible to dehydration or electrolyte imbalance through excessive sweating. It’s an effect that the director of the CDC’s Environmental Health and Hazards Program, in a 2010 interview with Scientific American, likened to that of a convection oven — heating people up by blowing hot air on them.
But other research has found that fans increase the temperature a body can handle by 3 to 4 degrees even at high temperatures. So at this point, the jury’s still out on whether a hot breeze is better than no breeze at all.
3. Cool by calorie
In hot weather you probably are less inclined to eat a big meal — and there’s good reason for that. Blood has to get diverted to your gut when you digest food, and the bigger the meal, the longer the diversion. That’s a problem for heat dissipation because less blood at the skin’s surface means less blood getting cooled off.
Smaller, more frequent meals may be a better idea than the typical three big ones, according to a 2004 review. What’s more, you might want to avoid protein-dense foods, which, likewise, take more time to digest.
But no need to head for the hot sauce. Though studies have found that capsaicin, found in chili peppers, can activate blood vessel dilation and lower core body temperature in rats, the same doesn’t hold true in humans, a study found.
4. Frigid forearms
A cool shower can help on a hot day, but if that’s not accessible maybe just dunk your arms in cold water.
In response to cold, your blood vessels constrict, which means less blood is getting chilled. But research suggests people can override this reflex by cooling only some parts of their bodies. A 2013 review looked at various extremities and found that submerging arms up to the elbow in cool water is the most effective method for dropping body temperature. A study of this technique during Army training found that it reduced the severity of heat illnesses during arduous work days.