Diet Soda Mixers Get Us Drunker Than Regular Soda Mixers

The unforeseen side effects of artificial sweeteners

The unforeseen side effects of artificial sweeteners

Joel Olives/Flickr

Our anti-soda opprobrium is overwhelmingly aimed at the pure stuff: With around 40 grams of sugar per can, to say nothing of larger portions, it's hard to find any redeeming qualities in regular soda.

But a forthcoming study in the journal Alcoholism: Clinical & Experimental Research reminds us that diet soda isn't the smart solution it's sometimes made out to be. It may not directly cause us to gain weight -- although a small experiment demonstrated how artificial sweeteners may mess with our brain's reward center enough to drive us to eat more than we otherwise would -- but some studies have linked the drink to other health concerns, like a greater risk of depression. None are wholly convincing, but any "health benefits" that diet soda can be claimed to have exist only in comparison to regular soda.

The new study was conceived after researchers at the University of North Texas stood outside a bar as patrons stumbled out, surveying them on how much they'd had to drink, and what kind of drinks they'd ordered. When they gave them breathalyzer tests, they found that the people who had used diet soda as a mixer blew significantly higher readings.

Intrigued by these findings, researchers at Northern Kentucky University recreated happy hour in the lab, serving "social drinkers," over three separate sessions, Smirnoff vodka mixed with Squirt, mixed with diet Squirt, or, as a placebo, regular Squirt with a bit of vodka on top to make it smell alcoholic.

Each time (excerpt for the placebo test), the participants -- eight men and eight women -- consumed the same amount of alcohol, a dose predetermined to approximate intoxication at the legal level for driving. But drinks made with the aspartame-sweetened diet soda resulted in higher breath alcohol levels than with regular Squirt, by as much as 18 percent at the peak. This difference persisted for three hours after they'd had the drink.

Crucially, they also measured the participants' perceived levels of intoxication, including how willing they were to drive. The subjects, although displaying more impaired behavior on the diet Squirt, appeared wholly unaware of their increased level of intoxication.

Why would diet soda make us drunker? The researchers point to studies showing how the stomach treats regular soda "somewhat like food." Even though it consists entirely of empty calories, they believe it is still able to slow down the absorption of alcohol into the bloodstream. But artificial sweeteners don't act like food in any sense. Just as we become more intoxicated when we drink on a empty stomach, diet soda does nothing to mediate the body's absorption of alcohol.

The direct problems with this are obvious: People are already terrible judges of how intoxicated they are, and different mixers having different effects should make it even more difficult to try to keep track of how much one can have to drink and still be okay to drive.

And while people at bars might think of ordering diet drinks as the "healthier" option, this study is a good way of pointing out one way in which that really doesn't make sense. At best, diet soda is a big glass of nothing. At worst, it could be harming us, in ways that we have yet to fully understand.