Science says a slushy is one of the best ways to cool down on a hot dayWhether it’s a Slurpee, Frappuccino or frozen margarita, a slushy drink can bring your body temperature down fast on a hot day.
https://www.washingtonpost.com/climate-solutions/2024/08/26/slushy-cool-down-heat/
On a hot summer day, one of the most effective ways to cool your body is to drink a slushy.
Really, it could be any drink made from crushed ice: a slushy, a frappé, a frozen margarita. Even a snow cone or sorbet will do. The key, scientists say, is that it has to contain a lot of tiny chunks of ice that you can comfortably drink or swallow whole.
“You actually want to ingest little bits of ice,” said Matt Maley, an assistant professor at Loughborough University in England who tested the slushy cooldown method as part of a study he published in 2020.
Drinking a big cup of crushed ice can drop your internal body temperature by about 1 degree Fahrenheit within 20 minutes, according to Maley. “That’s quite a substantial reduction,” he said — especially when you consider that the difference between an average, healthy body temperature (98.6 degrees) and getting dangerously hot (100.4 degrees or more) is less than 2 degrees.
A separate 2014 study on Australian firefighters found that drinking a big slushy was just as effective at lowering core body temperature as sitting in a tub of cool water up to your bellybutton. Other papers have confirmed the slushy’s cooling power in cyclists and triathletes and suggested using it for soldiers.
“There is a lot of research showing that drinking cold beverages, especially ice slurries, cools the body’s core temperature,” said Larry Kenney, a physiology professor at Pennsylvania State University.
Here’s what to know if you want to cool off with a slushy this summer.
Can I just have an iced drink instead?
It’s a good idea to drink anything that will hydrate you on a hot day. But if you want to cool down as fast as possible, you don’t just want a drink that’s cooled with ice — you want to drink ice.
Swallowing ice takes advantage of a quirk of physics: Melting ice absorbs a lot of heat without warming up at all. In your stomach, a lot of your body heat will just go into breaking up the ice crystals — and then, once they’re all melted, you have a belly full of cold water that will gradually soak up even more heat from your body.
How big does the slushy need to be?
The amount of slushy you need to cool down depends on your weight.
Both Maley’s 2020 study and the earlier 2014 study used a similar formula that translates to about one fluid ounce per eight pounds of body mass. For the firefighters in the 2014 study, who weighed around 185 pounds, that would be 23 ounces, which is roughly one large Slurpee from 7-Eleven.
(Note: Don’t choke! Drink ice crushed into pieces that are easy to swallow.)
When should I drink a slushy to cool down?
You can drink a slushy right before you go out into the heat to prevent your body from warming up as much, or you can drink a slushy while you’re in the heat or after you’ve been outside to cool down quickly.
It doesn’t matter how fast you drink it, as long as you don’t let it melt. The firefighters in the 2014 study slurped their slushies in 15 minutes after exercising, while in the 2020 study, they sipped them over the course of half an hour before exercising. The results were the same: Their internal body temperatures dropped by about 1 degree Fahrenheit.
Does it matter if the slushy is sugary, caffeinated or boozy?
If you want to avoid sugar, caffeine and alcohol, you can get the same cooling effect by drinking a cup of crushed ice mixed with a little water. But if your slushy does have those ingredients, they won’t outweigh the cooling effect of swallowing a bunch of crushed ice.
Digesting caffeine and sugar can raise your core body temperature — but only a little, Maley said. “Even with the addition of caffeine slightly increasing core body temperature and a sugary drink increasing temperature, I don’t think that’s enough to offset that reduction you get from an ice slushy,” Maley said.
Alcohol, meanwhile, lowers your core temperature by increasing blood flow to your skin, which allows your body to release more heat.
That doesn’t mean that drinking a bunch of sugar, caffeine or alcohol is good for you or that you should have a spiked, sugary slushy every day this summer. Drinking lots of alcohol or caffeine can be counterproductive, since they tend to make you urinate more, which can dehydrate you and limit your body’s ability to cool down by sweating. But having one spiked or caffeinated slushy won’t make much of a difference, according to Kenney.
Use your common sense about when it’s a good idea to drink caffeine or alcohol. If you’ve been out in the heat all day and you’re feeling dehydrated, you might not want to spike your slushy. “On a personal level, I would say maybe just stick to water for the next hour or so,” Maley said.
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