Can liquorice be bad for you?

Liquorice extract comes from the plant Glycyrrhiza glabra. Liquorice extract is used as a sweetener and as a flavouring agent in some lollies, drinks – including herbal teas – and it's also available as a dietary supplement.

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Liquorice extract, especially when consumed in large quantities, can cause side effects. 

Glycyrrhizin in liquorice can increase blood pressure and cause the potassium levels in your body to fall. When that happens, you may experience abnormal heart rhythms, as well as high blood pressure, water retention and swelling (oedema), extreme tiredness and heart failure.

You're most at risk of side effects from liquorice and should avoid it if you have:

• high blood pressure, including high blood pressure during pregnancy
• heart failure
• kidney disease.

In general, a maximum of 100 mg/day of glycyrrhizin is recommended, which is about 60 to 70 g of liquorice sweets.

Liquorice can interact with some medicines used to treat high blood pressure or heart failure, such as:

• thiazide and loop diuretics (also called water pills)
• digoxin 
• corticosteroids.

It can also interact with some herbal supplements and rongoā Māori, so check with your doctor or pharmacist if you have questions about possible interactions between liquorice and a medicine or supplement you're taking.