Your favorite cocktail could be making you more than just tipsy.
The Moscow Mule — a mixed drink consisting of vodka, ginger beer and lime juice that’s normally served in a copper mug — can lead to copper poisoning.
The Food and Drug Administration’s Food Code, which provides food safety regulations, states that copper shouldn’t come into contact with foods with a pH lower than 6. That includes vinegar, fruit juice and wine. Lime juice, a staple of the Moscow Mule, typically has a pH between 2 and 2.4.
When copper mixes with acidic edibles, the metal can leach into the food or beverage. Copper poisoning symptoms include stomach pain, diarrhea, vomiting and jaundice.
Health officials in Iowa consider potential copper poisoning enough of a health threat that they recently issued an advisory bulletin reminding anyone selling and serving alcoholic beverages in copper mugs of the federal guidelines and state regulations regarding the use of copper with food and drinks.
The bulletin states that cups with interior linings of copper and copper alloys such as brass may not be used with drinks with a pH lower than 6. Cups with copper just on the outside, however, are fine.
“The recent popularity of Moscow Mules, an alcoholic cocktail typically served in a copper mug, has led to inquiries regarding the safe use of copper mugs and this beverage,” the Iowa Alcoholic Beverages Division wrote in a statement. “…This means that copper mugs that have a copper interior may not be used with this beverage.”
Other drinks that shouldn’t be served in a copper mug — based on their pH levels — include apple cider, any citrus fruit juice, cranberry and pineapple juice, dark colas, Lipton iced tea and root beer.
As for why Moscow Mules are served in copper cups, legend credits a successful marketing campaign for the Smirnoff Mule that depicted the drink served in the mugs as boosting the beverage to one of the most popular cocktails of the 1950s and ’60s. The copper mug is now iconic — so serving the mule in anything else is kind of like serving champagne in a coffee mug.
And according to the product site Home Wet Bar, copper mugs make for the perfect chilled drink since the metal gets cold, insulating the cocktail. Home Wet Bar also states the copper enhances the flavors of the cocktail’s ingredients, but that just might be the deliciousness of a potentially dangerous chemical reaction.
Recently, Moscow Mules have resurfaced as a popular drink thanks to its Instagram appeal. Go for it — as long as your aesthetic doesn’t have a copper interior.