Mixing Diet Soda And Alcohol Saves A Few Calories, But It May Come With A Hidden Cost

Some Americans may try to cut down on a few calories by using diet soda as a mixer in their alcoholic drinks. But new research suggests that mixing a diet rum and coke could actually carry an unexpected risk: since diet soda contains less sugar, it may cause greater intoxication than full-calorie soda, even though the difference is barely noticeable while drinking it.

Sugar slows down alcohol’s absorption from the stomach to the bloodstream — so diet mixers can actually make people drunker than full-calorie mixers, even when combined with the same amount of alcohol, because they have less sugar in them. That’s why the new study’s lead researcher, Cecile Marczinski, found significant differences in Breath Alcohol Concentrations (BrAC) among people who mixed their alcohol with a full-calorie soda and those who used a diet soda:

So what was the motivation for the new study? “I wanted to know if the choice of a mixer could be the factor that puts a person above or below the legal limit,” writes Marczinski, who’s a professor at Northern Kentucky University.

And it turns out, diet soda might just push you past that tipping point. Marczinski’s study found that the average BrAC was .091 (at its peak) when subjects drank alcohol mixed with a diet drink. By comparison, BrAC was .077 when the same subjects consumed the same amount of alcohol but with a sugary soda.

“I was a little surprised by the findings, since the 18% increase in BrAC was a fairly large difference,” Marczinski tells [NPR’s] The Salt via email.

Marczinski also wanted to see if the participants in the study could feel a difference between the two mixers — essentially, whether or not they could tell that diet soda was making them drunker — and it turns out they couldn’t. Participants didn’t report that drinking the diet drinks made them feel any more impaired or intoxicated than they did after drinking the more sugary drinks. That could put them at an increased risk of drinking and driving, since they may not realize diet soda could have pushed their BrAC over the legal limit.

Of course, sugar isn’t the only ingredient that has a potentially hidden effect on alcohol consumption. Mixing alcohol with high levels of caffeine — typically present in popular energy drinks — also tricks consumers into thinking they’re less impaired than they actually are. Alcohol and energy drink combinations are increasingly sending young adults to the hospital, and the American Academy of Pediatrics recently began recommending that doctors attempt to mitigate the dangerous trend by talking to their adolescent patients about the risks of drinking alcohol with caffeine.


The American Beverage Association — which represents Coke, Pepsi, and Dr. Pepper, among other products — disputes the study’s findings. According to the ABA, Marczinski’s study “simply supports the long known fact that consuming calories — from any food or beverage — along with alcohol slows down its impact. If the study participants consumed alcohol with any other non-caloric beverage, including water or even club soda, the results would be the same.”

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