Liquorice and blood pressure

Liquorice contains a natural substance with a real effect on the body. That substance is glycyrrhizin, also called glycyrrhizic acid, which comes from the liquorice root used to flavour black liquorice: see is liquorice a root?

What glycyrrhizin does

The British Heart Foundation explains that glycyrrhizin can alter the body's levels of potassium and sodium, which help regulate fluid balance. Too much liquorice can therefore cause high blood pressure, fluid retention, muscle weakness and abnormal heart rhythms, increasing the risk of cardiovascular disease. Blood Pressure UK says it works through its effect on an enzyme in the kidney.

The good news is that the changes are not normally permanent. According to the British Heart Foundation, if you stop eating liquorice, your sodium, potassium and fluid levels should return to normal.

How much is too much?

• The guideline. European and World Health Organization guidance suggests that a maximum of 100 mg of glycyrrhizin a day is safe for most people, although some people may be affected by less.
• The catch. The British Heart Foundation points out that there is no way of knowing how much glycyrrhizin is in a liquorice product, because it is not shown on food labels. In one small study, 3.3 g of liquorice containing 100 mg of glycyrrhizin raised blood pressure over two weeks.
• A rough warning line. Blood Pressure UK warns that eating more than 57 g, about two ounces, of black liquorice a day for at least two weeks could lead to potentially serious problems, such as raised blood pressure.

Who should be careful

The British Heart Foundation advises people with high blood pressure or cardiovascular disease to avoid or limit liquorice. Blood Pressure UK says eating too much is a particular risk for people over 40 with a history of heart disease or high blood pressure, and that people of all ages should avoid eating large amounts of black liquorice over a short time.

A cautionary case

In 2020, doctors described in the New England Journal of Medicine how a 54 year old construction worker in Massachusetts died after eating a bag and a half of black liquorice every day for a few weeks. He had switched from red, fruit flavoured twists to the black liquorice version. He collapsed with dangerously low potassium and heart rhythm problems, and died the next day. Asked about the case, a spokesman for the confectioner Hershey said its products were safe to eat and made in full compliance with American food regulations.

What the label tells you

Food law sets out warnings for liquorice. A sweet containing glycyrrhizinic acid at 100 mg per kg or more must say it contains liquorice. Confectionery with 4 g per kg or more must add that people suffering from hypertension should avoid excessive consumption: see how to read a sweet label

Not every sweet with a liquorice taste gets it from liquorice root. Aniseed, for example, is a different plant: see is aniseed the same as liquorice?

We sell Liquorice Allsorts and soft liquorice twists in our pick and mix. Each sweet card shows its ingredients and allergens, and if you have high blood pressure or a heart condition, it is worth following the advice above.

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