Eating too much liquorice can cause allsorts of problems

Since I was a child I’ve been a fan of black liquorice. I love the stuff so much that my mum used to send it to me when I was a student living away from home.

Just as well I eat less of it now as the US Food and Drug ­Administration has warned too much may disrupt heart rhythm and spark high blood pressure.

The FDA’s warning applies very specifically to people aged over 40 who eat 2oz – about one eighth of a pack – of black liquorice a day for two or more weeks.

Black liquorice lovers like me can still enjoy the sweet in moderation, but if you’re mid bite and notice your heart is beating irregularly or you’re feeling weak, you should “stop eating it ­immediately and call your healthcare provider”, the FDA advises.

That’s a bit alarmist, isn’t it?

Black liquorice is made with extract from the root of the Glycyrrhiza glabra plant and it’s this that gives it its ­sweetness.

The root contains a compound called glycyrrhizin and it prevents potassium absorption so potassium levels may drop below normal levels (I also chewed liquorice root as a child).

The balance between potassium and sodium levels is key to healthy heart function. When potassium levels are too low, sodium levels rise too high. The imbalance can result in high blood pressure and upset the heart’s rhythm. The danger here is that abnormal heart rhythms greatly increase the risk of a heart attack.

If you really, really love liquorice as I do, the FDA says: “No matter what your age, don’t eat large amounts of black liquorice in one go.”

Incidents of black liquorice overdose are extremely rare. A case was reported in the New England Journal of ­Medicine in 1991 – doctors treated a 70-year-old man who had been eating between 60 and 100 pieces of black liquorice every day for the previous four years or so.

Another man, age 66, was admitted to hospital with high blood pressure and low potassium. It turned out that he was eating about 160 Fisherman’s Friend Extra Strong lozenges, which contain liquorice, each day.

But after a black liquorice binge ends, potassium levels typically return to normal.

Liquorice extract is a traditional treatment for heartburn and digestive problems, though proof of its usefulness is thin on the ground.

And by the way, red ‘liquorice’ is completely safe. It doesn’t actually include any liquorice. Without ­liquorice extract, it has no glycyrrhizin, and without glycyrrhizin, it doesn’t pose any health risks (beyond a horrible sugar overdose).