When you think of licorice, strings of black chewy candy may come to mind. Unfortunately, licorice is not just a benign ingredient in confections. True licorice -- which is not an ingredient in most licorice candies today -- contains glycyrrhizic acid, which can cause high blood pressure if ingested in large enough quantities. Avoiding true licorice is prudent if you have high blood pressure.
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How It Causes High Blood Pressure
Blood pressure is regulated by a complicated series of hormonal interactions. Cortisol is an important hormone that is degraded by the enzyme 11-beta-hydroxysteroid dehydrogenase. Glycyrrhizic acid inhibits this action. Blocking this enzyme leads to excessive levels of cortisol in the body. Cortisol itself can lead to higher blood pressure, but at higher levels cortisol is thought to raise blood pressure through acting on receptors for aldosterone. Aldosterone leads to elevated blood pressure by causing salt retention and blood vessel constriction.
How much licorice is too much? An August 2001 article published in the “Journal of Human Hypertension” addressed that question. Using three study groups, composed of a total of 64 participants, various doses were used to compare blood pressure response. Group one consumed 200 g of sweet licorice daily for two weeks; group two consumed 100 g daily for four weeks; and group three consumed 50 g daily for four weeks. One serving of licorice candy is approximately equivalent to 50 grams of licorice. All groups had a significant rise in systolic blood pressure, between 3.1 to 14.4 mm/Hg, in the first two weeks. Group one had the highest rise in systolic blood pressure.
Sources of Glycyrrhizic Acid
Glycyrrhizic acid is found in anything containing licorice root, or licorice extract, and it is not limited to confections. It is also a component of tea, over-the-counter supplements and over-the-counter cough preparations. Licorice containing glycyrrhizic acid is not sold in the United States, but candy purchased from other countries might contain it. Anise is a commonly used flavor substitute for licorice extract in black licorice, because it has a similar taste. Anise is not associated with high blood pressure. Look in the ingredient list for licorice root to determine if a food or medication is a source of glycyrrhizic acid.
Other Side Effects
Licorice has other effects on the body beyond blood pressure elevation. Through its interaction with 11-beta hydroxysteroid dehydrogenase, ingestion can lead to low blood potassium and metabolic alkalosis. Metabolic alkalosis is a condition where the body becomes more alkaline. As licorice is thought to work to loosen phlegm, it is used in cough preparations as an expectorant. Licorice is also thought to work as a mild laxative.
Handling High Blood Pressure
Licorice has been documented to elevate blood pressure. As high blood pressure is associated with heart disease and stroke, your physician will likely advise you on what you can do to lower it. This often includes medications, diet and exercise. If you have high blood pressure, the safest bet is to avoid ingesting foods and medications containing licorice.