Cold, bubbly drinks quench our thirst better than non-fizzy, lukewarm beverages. So says a new study from the Monell Center, an institution dedicated to researching taste and smell (more on them later). Low temperature and carbonation both reduce thirst, and therefore they may have an effect on how much we drink.
"We have a decent understanding of what turns thirst on," said lead author Paul Breslin, of Monell, "but need to better understand what turns it off so we can motivate the elderly and other at-risk populations to keep drinking their fluids."
To determine the effects off fizz and cold on thirst, 98 experimental subjects were deprived of food and drink for over 12 hours, overnight. Then they were given breakfast, along with a fixed volume—400 ml or around 13.5 ounces—of an "experimental beverage," before being given still, room-temperature water to keep drinking if they needed it. The amount of water they drank was recorded.
The experimental beverage varied in temperature, whether it was fizzy or not, and in acidity and sweetness. Menthol was also used to change the mouth perception of temperature, making a warm beverage feel colder when drunk. A second experiment involved participants drinking an unseen beverage through a straw, and being asked to estimate the amount that they had ingested.
The results showed that participants drank a lot less water from the jug after they'd had some fizzy room-temperature water. When the experimental beverage was just cold water, participants also drank a lot less extra water. Interestingly, for those subjects for whom menthol made water taste cooler, there was a similar effect to drinking real cold water. One thing to remember, though, is that the gas in the fizzy drinks might simply be filling up our stomachs.
Acidity, astringency, and sweetness had no measurable effect on thirst: Coldness and bubbliness were the only important factors. This is important, because it means that a glass of plain old seltzer, or carbonated mineral water, or just soda water out of a Soda Stream, is the best thing to quench thirst. (On the other hand, if you're dehydrated and want to drink a lot of water, you may not want to quench your thirst that quickly. Then you want room temperature water.)
Soda, therefore, is something you shouldn't drink. The extra sugar isn't necessary. That's important to note because the Monell Center is funded in part by corporate sponsors. It's not a list that makes you particularly confident in their pronouncements about food, including PepsiCo, the Sugar Association, the Coca-Cola Company, and various other beverage and even pharmaceutical companies. Given that this study concludes that flavoring the water doesn't help at all, the results don't look too suspicious. Then again, it's easy to imagine PepsiCo, Coca-Cola, and Asahi claiming that their fizzy (calorie-laden, not good for you) drinks are scientifically proven to quench thirst better than boring old tap water.
But we already know that thirsty humans prefer cold, fizzy drinks. Beer and soda are more appealing than lukewarm water on a hot day. This knowledge, then, could help us to help people at risk of becoming dehydrated—laborers, soldiers, and the elderly—but the study authors offer no ideas on how that may be achieved. At the very least, we might now be able to tackle the dehydration that comes along with a bad hangover, the parched feeling that never seems to go no matter how much water you glug down. Just make sure to stock the refrigerator with seltzer before a big night out.
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