SATURDAY REWIND: Diet soft drinks make cocktails unexpectedly more potent

The following article from the alcohol research news archive demonstrates how using low- or no-calorie sodas as mixers can boost blood alcohol concentration compared to the same cocktail with regular soda. (See full article here.) A couple points difference in BAC can make a difference when behind the wheel.


Artificially sweetened sodas, when used as cocktail mixers, make the drinks more potent, according to a study released in the journal Alcoholism: Clinical & Experimental Research . Specifically, researchers found that mixing alcohol with diet (sugar-free) soft drinks resulted in a higher blood alcohol concentration (BAC) than mixing alcohol with a regular (sugar-sweetened) soft drink.

Researchers gave college students vodka drinks with regular soda and with diet soda, and the diet soda group got more intoxicated – almost 20 percent more – than those who mixed regular soda with liquor. The sugar actually slows down the effects of alcohol, researchers say.

Sugar-containing drinks stimulate the stomach, delaying stomach emptying and, as a result, delaying absorption of alcohol into the bloodstream. Diet beverages, since they contain no sugar, do not trigger the stomach to delay emptying, allowing alcohol to reach the bloodstream more quickly.

Though it was a very small study, only eight women and eight men, the findings closely match previous research linking diet drinks and increased BACs. "The results were surprising," said Cecile A. Marczinski, assistant professor in the department of psychological science at Northern Kentucky University, and one of the lead investigators of the study. "We are talking about significant differences here," Marczinski said, adding that there may even be potentially harmful consequences for those who regularly request a diet soda with their spirits.

"In the long run, it's more harmful for your body to be exposed to a higher alcohol concentration than a few extra calories," she said. This could increase the incidence of alcohol abuse and the disease of alcoholism.

The students also completed computer tasks testing their reaction times after drinking, mimicking what they might face while driving. Those drinking the diet soda were slower to react.

No difference was noted between the genders, but the students said they felt the same no matter what they drank, even though tests showed the diet drinkers were about one-fifth more intoxicated. To put that in perspective, you'd have to add almost another shot of vodka to the sugar-sweetened drink to equal the potency of the diet drink mixture.

"Marczinski's findings are very consistent with what we've found in the field in a natural drinking environment. When the mixer is diet soda, the bar patrons tend to have somewhat higher intoxication levels than when they consume regular soda," says Dennis Thombs, professor and chair of the Department of Behavioral and Community Health, School of Public Health at the University of North Texas in Fort Worth.

Drinkers often mix diet soda and alcohol to save on calories. Calorie-counting drinkers might do better simply to limit their alcohol intake, since alcohol itself is packed with calories. (See this related article on alcohol calories.)

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