Dosage, Safety Issues & Interactions
A member of the pea family, licorice root has been used since ancient times both as food and as medicine. In Chinese herbology, licorice is an ingredient in nearly all herbal formulas for the traditional purpose of "harmonizing" the separate herbs involved.
The herb licorice contains a substance called glycyrrhizin. When taken in high enough amounts, glycyrrhizin produces effects similar to those of the natural hormone aldosterone, causing fluid retention, increased blood pressure, and loss of potassium. To prevent this, manufacturers have found a way to remove glycyrrhizin from licorice, producing the safer product deglycyrrhizinated licorice (DGL).
For supportive treatment of ulcer pain along with conventional medical care, the standard dose is two to four 380-mg tablets of DGL taken before meals and at bedtime. The same tablets can be allowed to slowly dissolve in the mouth for possible relief of mouth sore pain.
A typical dose of whole licorice is 5 to 15 g daily. However, we do not recommend the use of doses this high for more than a few weeks. For long-term consumption, about 0.3 g of licorice root daily should be safe for most adults. (See Safety Issues.) Individuals who wish to take a higher dose should do so only under the supervision of a physician.
For the treatment of eczema, psoriasis, or herpes, 2% licorice gel or cream is applied twice daily to the affected area.
Use of whole licorice has not been associated with significant adverse effects in the short term. However, two or more weeks of use may cause high blood pressure, fluid retention, and symptoms related to loss of potassium. Such effects are especially dangerous for people who take the drug digoxin or medications that deplete the body of potassium (such as thiazide and loop diuretics), or who have high blood pressure, heart disease, diabetes, or kidney disease.
Current evidence indicates that individuals who wish to take whole licorice on a long-term basis without any risk of these side effects should not consume more than 0.2 mg of glycyrrhizin per kilogram of body weight daily. For a person who weighs 130 pounds, this works out to 12 mg of glycyrrhizin daily. Based on a typical 4% glycyrrhizin content, this is the equivalent of 0.3 grams of licorice root.
Whole licorice may have other side effects as well. For example, it appears to reduce testosterone levels in men. For this reason, men with impotence, infertility, or decreased libido may wish to avoid this herb. Licorice may also increase both the positive and negative effects of corticosteroids such as prednisone and hydrocortisone cream. In addition, some evidence suggests that licorice might affect the liver's ability to metabolize other medications as well, but the extent of this effect has not been fully determined.
Whole licorice possesses significant estrogenic activity, and some evidence indicates that licorice increases risk of premature birth. For these reasons, it shouldn't be taken by pregnant or nursing women, or women who have had breast cancer.
Maximum safe doses for young children, nursing women, or those with severe liver or kidney disease have not been established.
It is believed, but not proven, that most or all of the major side effects of licorice are due to glycyrrhizin. For this reason, DGL has been described as entirely safe. However, comprehensive safety studies on DGL have not been reported.