Doctors said a man in the US has died after he ate a bag and a half of liquorice every day for several weeks.
Consuming a large amount of the confectionery caused the 54-year-old construction worker’s heart to stop, according to medics in Massachusetts.
They found he had dangerously low potassium levels, which led to heart rhythm problems.
The unnamed man collapsed and suffered cardiac arrest while having lunch at a fast food restaurant.
Emergency responders performed CPR and managed to revive him but he died the following day.
Doctors describing the case in the New England Journal of Medicine said glycyrrhizic acid in black liquorice was to blame.
It can cause very low potassium and imbalances in other minerals called electrolytes.
The acid is also found in many other foods and dietary supplements containing liquorice root extract.
“Even a small amount of liquorice you eat can increase your blood pressure a little bit,” said cardiologist Dr Neel Butala from Massachusetts General Hospital.
The patient had also recently changed the type of sweets he was eating.
He switched from red fruit-flavoured twists to another type made with black liquorice a few weeks before his death.
The US Food and Drug Administration (FDA) has warned eating as little as two ounces of black liquorice a day for two weeks could cause a heart rhythm problem, especially for people aged over 40.
“It’s more than liquorice sticks. It could be jelly beans, liquorice teas, a lot of things over the counter. Even some beers, like Belgian beers, have this compound in it,” said Dr Robert Eckel, a University of Colorado cardiologist.
The FDA allows up to 3.1% of a food’s content to have glycyrrhizic acid, but many confectionery and other liquorice products do not reveal how much of it is contained per ounce, Dr Butala said.
The NHS agrees that eating too much black liquorice can be bad for a person, especially for those over 40 who have a history of heart disease or high blood pressure or both.
It said on its website: “Eating more than 57g (two ounces) of black liquorice a day for at least two weeks could lead to potentially serious health problems, such as an increase in blood pressure and an irregular heart rhythm (arrhythmia).
“For most people, liquorice found in foods is safe to eat and safe when consumed in large amounts in medicines for short periods of time.”
The NHS added: “No matter how old you are, you should avoid eating large amounts of black liquorice over a short space of time.”
Jeff Beckman, a spokesman for the Hershey Company, which makes Twizzlers liquorice twists, said “all of our products are safe to eat and formulated in full compliance with FDA regulations”, and that all foods, including confectionery, “should be enjoyed in moderation”.