04/08/2023
When It's This Hot, What Should You Eat?
As temperatures continue to climb in what could become the northern hemisphere’s hottest summer on record, the summer of 2023 is all about finding any way to stay cool. And that includes turning to foods that will hopefully provide a little relief. While not a panacea for the heat, body-cooling foods and no-cook diets could help to lower body temperature and make record-breaking heat waves a little more bearable..
Living safely in consistently hot climates means staying hydrated, especially with chilled drinks or fruits. But there are other, more physiologically based—and even surprising—ways to make your diet more heat friendly. While the science behind diets, nutrition, and climate is still growing, changing global temperatures makes understanding the link between food and metabolism increasingly critical.
The contradictory cooling effect of spicy foods
One place to start is to explore how heat influences diets in warmer parts of the world. Why, for example, do the spiciest foods come from the hottest places on the planet? Think southeast Asian curries and peppers, and South American chilis. If spicy foods make you sweat and feel even hotter, why are they such a staple in warmer regions?
There’s a biological reason for that, says Dr. William Li, a former Harvard Medical School faculty member who has written a book about finding the right diet for your metabolism. What happens when you dig into a spicy dish? Your heart beats a little faster, you breathe a little harder, you start to perspire, and not just your mouth but your whole body can feel as if it’s on fire. And if you’re eating this dish and it’s above 90F outside, you’re really feeling the heat.
But sweating is the body’s physiological response to being too hot. “Our sole means of cooling is to sweat,” says Dr. Linda Shiue, an internist and chef who is director of culinary and lifestyle medicine at Kaiser Permanente San Francisco. Once you sweat, the perspiration evaporating moisture cools the skin. We’re not talking tens of degrees here—it’s fractions of single digits of change in temperature, but it’s still something. If the body’s core temperature starts climbing—which it does if you’re exposed to extreme heat for too long—sweating cools off the skin in an attempt to bring that core temperature down. Eating spicy foods jumpstarts that process, which is why they’re so popular in hotter regions of the world.
“Cultures in these parts of the world have known this for thousands of years,” says Li. “Their culinary culture triggers a hard-wired system that opens your pores and releases heat from the body. You feel temporarily hotter but that’s part of the package of cooling down.”
That hard-wired system involves a protein on our cells called TRPV1, which acts as a receptor for the active agents in spicy foods, such as capsaicin and capsinoids. The cells that have the highest concentration of TRPV1 receptors are on the tongue and the front of the roof of the mouth. Those spice agents trigger the receptors to send signals to the brain to release norepinephrine, a neurotransmitter primarily responsible for launching the fight-or-flight response. When this hyper-alert response is triggered, the body releases heat by triggering the sweats. That was helpful to human ancestors trying to outrun potential predators thousands of years ago…and also turns out to be useful in adapting to climate change today.
“Cultures in these parts of the world have known this for thousands of years,” says Li. “Their culinary culture triggers a hard-wired system that opens your pores and releases heat from the body. You feel temporarily hotter but that’s part of the package of cooling down.”
That hard-wired system involves a protein on our cells called TRPV1, which acts as a receptor for the active agents in spicy foods, such as capsaicin and capsinoids. The cells that have the highest concentration of TRPV1 receptors are on the tongue and the front of the roof of the mouth. Those spice agents trigger the receptors to send signals to the brain to release norepinephrine, a neurotransmitter primarily responsible for launching the fight-or-flight response. When this hyper-alert response is triggered, the body releases heat by triggering the sweats. That was helpful to human ancestors trying to outrun potential predators thousands of years ago…and also turns out to be useful in adapting to climate change today.
It’s not just spicy foods that can cool
There are also other, less obvious foods that work on TRPV1, but the data supporting how they are connected isn’t solid enough yet. There is anecdotal data suggesting, for example, that fruits such as durian and pineapple can help to cool, but in different ways. Durian may activate TRPV1 and generate perspiration, while an enzyme in pineapple called bromelain can slow digestion, which reduces the amount of energy, and therefore heat, generated by that process. In Mexico, says Shiue, people often season their helpings of fruit—which are helpful for staying hydrated when the weather is warm—with tajin, a blend of dried chilis, lime juice, and salt. Another popular seasoning in the region is chamoy, made from pickled fruit and chilis. “How brilliant is this as a way to keep yourself cool as well as hydrated?” she says. In India, known for its long periods of hot days, the beverage of choice is nimbu pani, a mix of lemon or lime juice, salt, and sugar that not only cools but replaces electrolytes lost when the body is over heated.'v
