Licorice (also spelled liquorice) raises blood pressure. If you want to continue eating licorice regularly, only select products flavoured with aniseed oil – not those that contain real licorice root extract. Also check any herbal teas you drink are not sweetened with licorice root.
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Licorice root extracts
Licorice (or liquorice) is a sweet confection made from extracts of the roots of the plant, Glycyrrhiza glabra. Native to the Mediterranean, the main flavour of liquorice root comes from anethole, a substance that has a similar taste to anise.
The sweetness and blood pressure raising properties of licorice are due to high quantities of glycyrrhizin (glycyrrhizic or glycyrrhizinic acid which makes up to 9% of licorice root’s weight. Glycyrrhizin is 50 times sweeter than sucrose sugar, and is commonly used in herbal teas and confections in place of sugar.
While licorice root has beneficial actions in that it is a source of plant oestrogens antioxidant flavonoids, and has antiviral action, but it is best avoided if you have hypertension as it consistently causes blood pressure to rise. Individuals with pre-existing hypertension and heart disease are more sensitive to this effect.
Licorice and blood pressure
Two forms of licorice extracts are available: those that contain glycyrrhizin, and deglycyrrhizinated liquorice (DGL) which have different uses.
DGL extracts are used medicinally to heal mouth ulcers, treat sore throat (in the form of lozenges), reduce acid indigestion (by increasing the production of mucus to line the stomach), and as an expectorant to help cough up respiratory phlegm. This form of liquorice does not raise blood pressure.
Glycyrrhizin-intact licorice is used as a sweet flavouring, and to stimulate the adrenal glands during times of stress and convalescence. A breakdown product of glycyrrhizin, known as glycyrrhetenic acid, is responsible for its pronounced blood pressure raising action. This substance blocks an enzyme that normally inactivates cortisol stress hormone, and prevents its conversion to cortisone in the kidneys. This direct effect on the kidneys leads to sodium retention, loss of potassium, and an increase in blood pressure – a condition known as pseudoaldosteronism. The effect is so powerful, that licorice has even been used to reduce the side effects of the drug, spironolactone (a powerful diuretic effect leading to low blood pressure).
Licorice can dangerously raise blood pressure
Doses of as little as 75 mg of glycyrrhizin (equivalent to 50 g of standard liquorice confectionary) per day can significantly increase systolic blood pressure within two weeks, by an average of 3.1 mmHg. As the dose of licorice increases, blood pressure rises in a linear fashion so that eating 200g licorice (equivalent to a daily intake of 540mg glycyrrhizin) increases systolic blood pressure by an average of 14.4 mmHg.
Another study found average blood pressure rises caused by regular consumption of licorice were in the region of 7/4 mmHg.
Different people respond in different ways, but eating licorice regularly will increase your blood pressure, and those with existing hypertension are most susceptible to this effect.
There are numerous case reports of people being admitted to hospital with a licorice-induced hypertensive crisis. In one case, a woman whose hypertension was previously well-controlled on medication was admitted to an emergency department with a blood pressure over 200/140 mmHg. Despite intravenous medications her blood pressure did not fall to safe levels until after five days in an intensive care unit. It turns out she had been eating large amounts of Snaps licorice (two to four boxes a day, every day) for six months.
In another case, a 45-year-old woman developed a high blood pressure of 62/82 mmHg and headaches after drinking up to six cups of licorice tea per day as a substitute for caffeinated tea and fruit-based infusions.
One woman almost died after being admitted to the emergency department with fluid retention causing gross swelling of the face and lower limbs and hypertension. The initial presumed diagnosis was a hormonal imbalance known as Cushing’s syndrome in which levels of aldosterone hormone are raised. It was later discovered that she was eating ‘lethal’ raw licorice lollies prescribed by a herbalist a month previously.
How much licorice is safe?
If you have hypertension, it’s wise to avoid licorice-containing products altogether, and select products flavoured with aniseed. Glycyrrhizin-intact licorice needs to be stopped slowly, rather than suddenly, to prevent a rebound effect on adrenal function if used in high doses.
The European Scientific Committee on Food have advised that regular glycyrrhizin doses of 100 mg/day are a risk to health, and suggest a safe average daily intake of no more than 10 mg/person/day. This amount is equivalent to less than half a cup of liquorice tea or just 6 g of liquorice confectionary daily.
In the UK, the Food Standards Agency requires any drink containing more than 50 mg/L of glycyrrhizin to carry the warning: ‘Contains liquorice—people suffering from hypertension should avoid excessive consumption.’
Glycyrrhizin-intact liquorice should not be used by anyone with liver disease, low potassium levels, kidney failure or high blood pressure, or by those taking antihypertensive medication (especially diuretics) or digoxin. Do not consume licorice during pregnancy – cases of licorice-induced high blood pressure (pre-eclampsia) have occurred.
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