Fabaceae
Glycyrrhiza glabra
Liquorice · Licorice
- Part used
- root
- Native range
- Southern Europe, western and central Asia
- Morphology
- A perennial legume to a metre and a half, with pinnate leaves, pale blue-violet pea flowers and a deep spreading root system that is the part harvested.
What is in it
Evidence
Deglycyrrhizinated liquorice has some evidence in dyspepsia. Topical preparations show modest effects in eczema. Most traditional uses remain untested. The best-characterised pharmacology is the adverse one.
Safety
Glycyrrhizin inhibits the enzyme that protects the mineralocorticoid receptor from cortisol, producing apparent mineralocorticoid excess: potassium loss, sodium and water retention, hypertension, and in severe cases muscle weakness, arrhythmia and cardiac arrest. This occurs at intakes achievable from confectionery, and cases from eating liquorice sweets are documented every year, including deaths.
Interactions: Potentiates potassium loss from thiazide and loop diuretics; Opposes antihypertensives; Raises digoxin toxicity risk through potassium loss; Interacts with corticosteroids
Regulatory: Permitted as a food and as a listed medicine ingredient. Several regulators including the EFSA and the US FDA have issued specific consumption warnings.
How the traditions classify it
Three systems, rating the same plant. Where they disagree, none of them is correcting the others — they are separate frameworks that arrived at their categories independently.
Historical use
Found in Tutankhamun’s tomb and recorded in Assyrian tablets. Used across every tradition it reached for cough, sore throat and stomach complaints, and universally as a sweetener and a corrector of other medicines.
Recorded as history and attributed where possible. Long use establishes that a plant was widely used, not that it worked, and not that it was safe.
Worth knowing
Liquorice is the plant most likely to harm someone who does not think of it as a medicine at all.
The mechanism is precise. Cortisol and aldosterone bind the same receptor, and the kidney keeps them apart with an enzyme that converts cortisol to an inactive form. Glycyrrhizin blocks that enzyme, so cortisol floods a receptor meant for aldosterone, and the body behaves as though it is producing far too much of a salt-retaining hormone.
The threshold is low enough that confectionery reaches it. The published case reports are mostly not about herbal medicine; they are about people who like liquorice sweets, and the US FDA issues a seasonal warning about it around Halloween.
It is also the most-used herb in Chinese formulas, included in most of them specifically to moderate the other ingredients — a corrective that turns out to have a sharp pharmacology of its own.
Nomenclature verified against GBIF backbone taxonomy.