Question: What makes you more drunk, vodka mixed with Coke, or vodka mixed with Diet Coke? Sounds like a trick question, but the answer isn't about slipping more vodka into one of the glasses and disguising it with the sweet taste of non-diet soda. A recent scientific study reported on my Smithsonian Mag found that diet soda, when mixed with alcohol, actually leads to higher breath alcohol concentration than a regular soda mixer. And not just a little higher--18 percent higher. In the tests, that was the difference between a legal-for-driving blood alcohol concentration and a DUI.
The experiment involved 16 people drinking .03 ounces of vodka per pound of body weight, with half of the group getting diet mixers and the other half getting regular soda (Diet Squirt and Squirt, specifically). All of the results pointed to diet drinkers being more intoxicated: their breath alcohol content was notably higher and they had slower reaction times in a computer test.
Worse, both groups were asked to describe how drunk they felt, and the diet drinkers rated themselves the same as the regular soda drinkers. "Subjective measures indicated that participants appeared unaware of any differences in the 2 alcohol conditions, given that no significant differences in subjective ratings were observed for the 2 alcohol conditions. No gender differences were observed for BrACs, and objective and subjective measures," observed the study's authors.
The study still leaves a nagging question, of course: Why? What's the difference between diet soda and regular soda? Aspartame and sugar, most likely. One of Smithsonian Mag's commenters pointed out that fructose increases the rate of alcohol metabolism. No such luck with diet, which means you'll face a dilemma with that next mixed drink: Let the sugary soda go straight to your gut, or stick with diet and be drunk by the second glass?