Licorice (Glycyrrhiza glabra) root contains glycyrrhizin (also called glycyrrhizic acid or glycyrrhizinic acid) and a mixture of the potassium and calcium salts of glycyrrhizic acid. Glycyrrhizin is metabolized to the active glycyrrhetinic acid in the intestine. Deglycyrrhizinated licorice (DGL) has had glycyrrhizin removed. Licorice is a purported galactogogue, and is included in some Asian proprietary mixtures to increase milk supply;[1] however, no scientifically valid clinical trials support this use. In fact, licorice usually reduces serum prolactin,[2] which might decrease milk production in the early stages of lactation. Women taking licorice have experienced elevated blood pressure.[3] Galactogogues should never replace evaluation and counseling on modifiable factors that affect milk production.[4,5] Some mothers in Turkey reportedly use licorice to improve the taste and quality of their milk.[6]
Glycyrrhizin is detectable in the breastmilk of some women taking licorice, but studies measuring glycyrrhetinic acid have not been performed. Licorice has been used safely and effectively in combination with other herbs given to infants as a tea for the short-term treatment of colic.[7] However, two infants whose mothers had an excessive intake of an herbal tea that contained licorice had signs of anethole toxicity.[8] Because both of these papers reported on herbal mixtures, the effect(s) of licorice alone cannot be determined. Licorice and licorice extract are "generally recognized as safe" (GRAS) as foods by the U.S. Food and Drug Administration. Long-term, excessive use of licorice can cause hypertension, hypokalemia, and disturbances of adrenal hormones, and therefore should probably be avoided during nursing.
Dietary supplements do not require extensive pre-marketing approval from the U.S. Food and Drug Administration. Manufacturers are responsible to ensure the safety, but do not need to prove the safety and effectiveness of dietary supplements before they are marketed. Dietary supplements may contain multiple ingredients, and differences are often found between labeled and actual ingredients or their amounts. A manufacturer may contract with an independent organization to verify the quality of a product or its ingredients, but that does not certify the safety or effectiveness of a product. Because of the above issues, clinical testing results on one product may not be applicable to other products. More detailed information about dietary supplements is available elsewhere on the LactMed Web site.