Despite the name, not all black licorice, scientifically known as glycyrrhiza glabra, actually contains licorice. Much of the black licorice sold today contains anise, which has a similar smell and taste rather than real licorice root. Because the active ingredient in black licorice, glycyrrhiza, can have harmful effects on your heart, especially if you have pre-existing heart disease, many manufacturers no longer use it in their products. Do not consume black licorice containing glycyrrhiza without your doctor's approval if you have any type of chronic disease.
Components
Glycyrrhiza, found in the root of the licorice plant, makes up between 5 and 9 percent of the plant, according to biochemist Holly Phaneuf, PhD, author of "Herbs Demystified." Long used for medicinal purposes to treat respiratory and digestive system problems, licorice is used in teas, capsules and extracts as well as in black licorice. Deglycyrrhizinated licorice, or DGL, which has the glycyrrhiza removed, does not have the same potentially harmful heart effects as black licorice with glycyrrhiza.
Effects
Glycyrrhiza in the form of glycyrrhizin or glycyrrhizinic acid in licorice inhibits enzymes called short-chain dehydrogenase reductases, or SDRs for short. These enzymes play a role in a number of chemical reactions. Some of the enzymes SDRs inhibit include those that balance sodium and potassium concentrations. Harmful symptoms of licorice appear to be caused by the blocking of an enzyme that normally limits the effects of cortisol, a steroid, on the kidney. Cortisol binds to aldosterone receptors in the kidney, causing effects similar to an excess of aldosterone -- a hormone that regulates blood pressure and fluid balances.
Symptoms
Symptoms that black licorice can cause include fluid retention, low potassium levels, high blood pressure, headaches and fatigue. Excess fluid can cause or worsen heart problems, especially in people who have congestive heart failure and whose hearts can't pump extra fluid effectively. Having to pump harder and more frequently to move the fluid through the body further weakens the heart muscle. High blood pressure can also contribute to heart disease, including heart attack or stroke. Since potassium helps regulate your heartbeat, low potassium levels can cause potentially fatal irregular heartbeats.
Considerations
Avoid licorice altogether if you have any type of heart or kidney disease, high blood pressure, low potassium levels or high blood pressure. Black licorice that contains glycyrrhiza can also interfere with heart and blood pressure medications as well as steroids and diuretics. Even if you don't have heart disease, limit licorice consumption to 100 g per day for no more than six to eight weeks at a time and watch for side effects, Phaneuf advises.
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