People shouldn't eat more than 100mg of glycyrrhizic acid a day

It follows the case of a 56-year-old woman who was admitted to hospital after overdosing on liquorice.

The woman from Yorkshire went into muscle failure, a potentially fatal condition, after eating too much Pontefract cake.

Writing in the Postgraduate Medical Journal, doctors said she had been eating the liquorice sweets to relieve chronic constipation.

Dangerous condition

"She had been eating a packet of sweets a day, about 200g," said Dr Raja Hussain of Pontefract General Infirmary.

"Her potassium levels were dangerously low and her muscles were very weak. She also had high blood pressure, which is dangerous because it can lead to stroke."

Liquorice is good for you in moderation

Sinead O'Hara,

Royal Homeopathic Hospital London

"She was up and walking about within four days," Dr Hussain told BBC News Online.

The active ingredient in liquorice, glycyrrhizic acid, is found in a variety of products, including herbal remedies.

Manufacturers claim it can relieve constipation, cold, flu and allergy symptoms and may even help people with chronic fatigue or ulcers.

It is also found in smaller quantities in confectionery, toothpaste and some herbal teas.

Cigarette and drugs manufacturers sometimes use it to improve the taste of their products.

Some brands of chewing gum can contain 24mg of glycyrrhizic acid while some herbal teas can contain up to 450mg per litre.

A report by the European Commission published earlier this year suggested that people should not consume any more than 100mg of glycyrrhizic acid a day.

Studies have shown that it can increase blood pressure or cause muscle weakness and chronic fatigue. Other problems include headaches or swelling.

Recent research suggested it can also lower testosterone levels in men, affecting their mood and sex drive.

"Like everything else, liquorice is good for you in moderation," said Sinead O'Hara, principal pharmacist at the Royal London Homeopathic Hospital. "But too much of it is quite toxic."

Haribo, one of the companies that manufacture Pontefract cake, said people shouldn't eat too much of it.

"Haribo advises, as with any other food, liquorice products should be eaten in moderation," said marketing manager Christian Freund.