Licorice products that include glycyrrhizin may increase blood pressure and cause water retention and potassium deficiency.46 Some people are more sensitive to this effect than others. Long-term intake (more than two to three weeks) of products containing more than 1 gram of glycyrrhizin (the amount in approximately 10 grams of root) daily is the usual amount required to cause these effects. Consumption of 7 grams licorice (containing 500 mg glycyrrhizin) per day for seven days has been shown to decrease serum testosterone levels in healthy men by blocking the enzymes needed to synthesize testosterone.47 However, in another study, a similar amount of licorice had only a small and statistically insignificant effect on testosterone levels.48 As a result of these possible side effects, long-term intake of high levels of glycyrrhizin is discouraged and should only be undertaken if prescribed by a qualified healthcare professional. Consumption of plenty of fresh fruits and vegetables to increase potassium intake is recommended to help decrease the chance of potassium deficiency. According to the German Commission E monograph, licorice is inadvisable for pregnant women as well as for people with liver and kidney disorders.49
De-glycyrrhizinated licorice extracts usually do not cause these side effects since 97% of the glycyrrhizin has been removed.