Science gives you yet another reason to order whisky

You usually order a drink to unwind after a tough day. But here’s something you should know about your favorite after-work beverage that might not be quite so relaxing: The drinks you order at the bar might be chock full of germs, according to a new Italian study published in the Annals of Microbiology.

In the study, researchers tested 60 samples of ice cubes produced at industrial facilities, restaurants and bars, and at home. They discovered the ice was contaminated with 52 different strains of bacteria, some of which can cause infections in humans—and restaurant and bar ice were the germiest offenders.

Then, the researchers infected ice cubes with four bacterial strains that were particularly dominant during their initial testing to see if they could survive in common drinks. They added the germy ice cubes to vodka, whisky, martinis, peach tea, tonic water, and Coke, and then analyzed the samples for bacterial counts.

The results? Across the board, there was a significant reduction in the number of bacterial cells once the ice was added, which the researchers attribute to varying anti-microbial effects of factors like alcohol, carbonation, and pH levels.

But there was a big difference in the drinks. In the vodka and the peach tea, all four of the bacterial strains survived, and two strains persisted in both the martinis and the Coke. And just one strain survived and grew in the tonic water.

But the least germy of all was the whisky: None of the bacterial strains on the ice cubes survived after they were added to the whisky.

That’s likely due to the acidic content—a pH of 4.2—of the whisky, as compared to the more neutral (pH of 6) vodka, the researchers say. The more acidic a beverage is, the less likely bacteria is to survive or multiply.

While this study looked at bacterial content, it didn’t look at how likely these results were to make you sick. So it’s impossible to say whether the bacterial growth seen in even the germiest drinks, like the vodka and the peach tea, would have definitive health implications.

Still, some of the bacterial strains detected in the ice in the initial testing have been linked to human infection, like B. cereus, which can cause food poisoning. So until more research is done looking at how likely these bacteria counts are to make you sick, it can’t hurt to order your vodka either straight or in a cocktail without ice—and if you’re looking for something with a little clink, then whisky on the rocks may be your safest bet.