A cautionary note regarding glycyrrhiza (licorice root)

Effects of Natural Health Products on Blood Pressure

OBJECTIVE:

To review the scientific literature to identify reports of the effects of natural health products (NHPs) on blood pressure. DATA SOURCES: Electronic databases (MEDLINE [1965–May 2004] via PubMed, the Cochrane Library [1995–May 2004], International Pharmaceutical Abstracts [1970–May 2004], Iowa Drug Information Services [1965–May 2004]) were searched using the key words medicine, herbal plants, medicinal plant preparations, phytotherapy, angiosperms/therapeutic use, gymnosperms/therapeutic use, ethnopharmacology, pharmacognosy, blood pressure, hypertension, hypotension, and diuretic. Searches were not limited by date, language, or publication type. Review articles and texts, as well as reference lists of relevant articles, were used to identify additional reports.

STUDY SELECTION AND DATA EXTRACTION:

Articles (English-language after 1980) were assigned to the following categories: human study, case report, animal study, in vitro study, or theoretical prediction based on chemical constituents. Discussions of mechanisms of action were noted.

DATA SYNTHESIS:

A comprehensive search of the scientific literature identified NHPs capable of affecting blood pressure. Case reports and clearly defined mechanisms of action provided strong evidence for the ability of ephedra and licorice to increase blood pressure. Coenzyme Q10 was reported to decrease systolic and diastolic blood pressure, although the mechanism is unclear. The clinical significance of the blood pressure effects of other NHPs is unclear due to lack of conclusive in vivo data, as well as substantial variability in the chemical content of preparations of NHPs.

CONCLUSIONS:

Among published information, there is little definitive evidence with regard to the impact of NHPs on blood pressure. Additionally, effects may vary in a given patient with the formulation and standardization of a particular product. Until research better characterizes the effect of NHPs on blood pressure, patients should be encouraged to talk with their healthcare provider before starting or stopping any herbal product.