Effects of prolonged ingestion of graded doses of licorice by healthy volunteers

Abstract

Licorice can induce a hypermineralocorticoid syndrome. Current literature usually refers to the effects of sweets containing glycyrrhizin, but little is known about the consequences of a prolonged intake of "pure licorice". We administered graded daily doses of dried, aqueous extract of licorice root, containing 108, 217, 380 and 814 mg of glycyrrhizin, to 4 groups of 6 healthy volunteers of both sexes for 4 weeks. No significant effects occurred in groups 1 and 2. After 2 weeks, side effects leading to withdrawal from the protocol occurred in a female in group 3 (headache), a male with a family history of hypertension in group 4 (arterial hypertension), and a female also taking oral contraceptives in group 4 (hypertension, hypokalaemia and peripheral edema). In group 4, transient reduction in kalaemia and increase in body weight were found after 1 and 2 weeks, respectively. A depression of plasma renin activity occurred in groups 3 and 4. In healthy subjects, only the highest doses of licorice led to untoward effects. These were favoured by subclinical disease or oral contraceptives, and were less common and pronounced than what has been reported after the intake of glycyrrhizin taken as such or as a flavouring agent in confectionery products.