Q: I’ve heard that warm or hot beverages can help cool you off on a hot day. Is that true?
A: It sounds counterintuitive, but a cup of hot tea, say, may help on a hot day. Certain nerve receptors in the mouth are activated by heat, and this can trigger the brain’s thermoregulatory center to induce sweating. Evaporation of sweat cools the skin and helps lower body temperature. In a small Canadian study published in Acta Physiologica in 2012, male cyclists stored less body heat (which would correspond to a lower core body temperature) when they consumed a warm drink (122°F/50°C), compared to when they consumed cooler drinks, presumably because more heat was lost through evaporative cooling than was added by the warm beverage.
But if you’re in a highly humid environment, sweat doesn’t evaporate from the skin as well, in which case it would be better to drink cold beverages, like an iced tea.
Another possible option to help keep you cool: Eat spicy foods. Chili peppers, black pepper and even ginger can also make you sweat, due to the same nerve receptors that are activated by warm beverages. At first, you may feel warmer, but as you start to sweat and the moisture evaporates, you’ll feel cooler. This may partly explain why the cuisines in hot regions, such as Mexico, India and Thailand, tend to use a lot of hot, spicy ingredients. (Of course, that also masks the taste of spoiled food.)
Still, there are no hard and fast rules about what to eat or drink to cool down in hot weather; the research is sparse and inconsistent. Plus, some things may just make you feel cooler subjectively, while others actually lower your body’s thermostat. What is clear is that when it’s hot out, it’s important to stay hydrated: that means drinking lots of fluids—hot or cold.