One of the trendiest drinks of 2017 is the Moscow Mule: a refreshing mix of vodka, ginger beer and lime juice.
Much of the cocktail’s appeal is down to the fact it’s often served in very Instagram-friendly copper-coloured mugs.
But now a US state department has issued a warning that these pretty vessels could give you food poisoning if they have not been specially made for cocktails.
The stark message comes from the state of Iowa’s Alcoholic Beverages Division, which has warned that copper and copper alloys are poisonous if consumed.
When these metals come into contact with food or drink with a pH level lower than 6, copper may leak into the edible substance and can be accidentally consumed.
The warning states: ‘High concentrations of copper are poisonous and have caused foodborne illness.’
The pH level of a Moscow Mule is well below 6, which is why Iowa and several other states have issued the warning as these cocktails are often served in copper mugs.
The Food and Drug Administration’s Moral Food Code, which Iowa and many other US states have adopted, has banned copper and copper alloys from coming into contact with foods that have a pH level lower than 6 because of the risk of poisoning.
However, this doesn’t mean that you can never drink a Moscow Mule from a copper mug.
If a copper-colored mug is lined with another metal, such as nickel or stainless steel, then the copper cannot leak into the food or drink and give you food poisoning.
But it’s important to check if your vessel has a lining before you start to drink.
The Alcoholic Beverages Division wrote in its public warning: ‘Copper mugs lined on the interior with another metal, such as nickel or stainless steel, are allowed to be used and are widely available.’