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Self-Control Slipping Away? Rinse. Spit. Repeat.

Australian researchers find rinsing one’s mouth with a glucose solution helps restore depleted self-control.
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Do you feel yourself losing control? Are you inches away from indulging in fattening food, or releasing a torrent of obscenities at a noisy neighbor?

Well, go wash out your mouth. Not with soap: with soda.

That’s the startling implication of newly published research from Australia. Psychologist Martin Hagger of Curtin University in Perth reports the key to self-restraint may be as simple as gargling with glucose.

In line with previous research, his study finds self-control is a limited resource, one that is a struggle to sustain over long periods. Also like previous studies (including a fascinating one involving dogs), it finds a connection between this all-important ability and the body’s response to glucose, the most common form of sugar.

But while other studies have found eating something sweet may replenish self-control—an ironic prescription for a dieter trying to stay on the wagon—this one argues swallowing a sugary substance isn’t necessary. Simply swishing it around in your mouth will do.

“This might be of important practical value,” Hagger and coauthor Nikos Chatzisarantis write in the journal Personality and Social Psychology Bulletin. “A glucose mouth rinse may be very useful to those who are constantly attempting to regulate their behavior (e.g. dieters, smokers) or are frequently having to exert self-control (e.g., workers employed to engage in boring or difficult tasks).”

Hagger describes five experiments that provide evidence in support of his thesis. In one, the participants (32 undergraduates) “were asked to read a boring passage of text in an expressive fashion,” an exercise that requires a high degree of self-control. They then rinsed their mouths out with either a glucose or a sugar-free solution.

Afterwards, they were given 20 minutes to solve a series of six anagrams—three of which were unsolvable. They could give up at any time, but they had to press a buzzer before leaving the room.

The results: Those who rinsed their mouths with glucose solution kept trying to solve the anagram after their peers had given up. They spent, on average, more than 15 minutes on the task before pressing the buzzer, whereas those who had gargled with the non-glucose solution spent an average of 11 minutes.

Another experiment featured 48 high school students, who began by squeezing a handgrip apparatus for as long as possible. They were then assigned one of two versions of a simple task, in which they had to name the color of letters that popped up on a screen.

For half the participants, the color of the letters was different from the color the letters spelled out (for instance, the word “blue” was spelled in green letters). This required a high degree of focused attention, depleting their self-control resources.

The students then were randomly assigned to use either the glucose or non-sugar mouth rinse. Finally, they once again squeezed the handgrip for as long as possible.

Among the kids assigned the simple version of the task, those who used the glucose rinse held the handgrip for just a few seconds longer, on average, than those who used the non-sugar rinse. But among those who had completed the difficult version, there was a huge difference in average times.

Those who had used the placebo rinse gave up after an average of 15 seconds; those who had used the glucose rinse averaged over 35 seconds. Even though it wasn’t swallowed, that jolt of glucose apparently restored their depleted willpower, allowing them to far outscore their peers.

What’s going on here? “Neuroimaging data indicate that the presence of glucose in the oral cavity is associated with increased activation in … brain regions associated with reward, motivation, and the regulation of motor activity,” the researchers write. The signal sent by the presence of glucose may provide “a rewarding stimulus” that promotes “increased effort and motivation,” they add.

They also point to previous research suggesting that “the presence of glucose in the oral cavity increases athletes’ physical performance on endurance time trials.” These results may explain why.

So, will glucose mouth rinses become a part of diet plans, and anger-management programs? Perhaps. More research will be needed to confirm these results, and to determine whether there are more practical means of introducing glucose into the mouth (perhaps specially formulated chewing gum).

However promising it may sound, we can think of one influential group of professionals who will be appalled by this proposal. Dentists who are reading this are no doubt quietly seething—and thereby rapidly depleting their limited stock of self-control.