Bad for the Teeth, but Good for the Mind

If your mind is feeling worn out (a phenomenon known as ego depletion) but don’t have time to wander around in nature, science now offers an alternative: gargling with sugar water.

The power of sugar has been hinted at since 2007, when one study showed that drinking sugar could restore mental muscles that had been worn out with effort. The original reasoning behind this help was that sugar is the fuel of the brain, so if we metabolize that sugar it will restore our brain’s energy and so restore our minds. The most recent evidence, though, shows that the sugar doesn’t even have to be metabolized; it’s enough just to gargle with it.

College students must have enjoyed being in this study: First they wore out their self-control by crossing out all the e‘s on a page from a textbook, and then they completed the classic Stroop task, in which you have to name the color of ink a color name is printed in.  The twist to the Stroop task was that students swished lemonade in their mouths while they did it (and identified colors by pushing buttons, since naming colors with a mouthful of lemonade has a serious potential for disaster). Students who swished with sugary (glucose-sweetened) lemonade were much faster when the color ink and word name didn’t match, while students who swished with artificially sweetened lemonade showed evidence of ego depletion.

How could gargling have such a useful effect? The thought is that sugar in the mouth triggers receptors associated with reward, which in turn activate parts of the brain that are helpful in self-control (because they also play a role in motivation).

Personally, I’ll stick with a walk in nature most of the time, and I’m sure my dentist appreciates the impact he’s having on my life choices. But the next time I’m on a long plane ride, trying to get some work done, I’ll feel a little less guilty requesting a sugary soft-drink as my in-flight beverage.
Sanders, MA, Shirk, SD, Burgin, CJ, & Martin, LL (2012). The gargle effect: rinsing the mouth with glucose enhances self-control. Psychological Science, 23, 1470-1472 DOI: 10.1177/0956797612450034


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