Eating small amounts of licorice, in keeping with the World Health Organization’s suggested daily intake, may still cause high blood pressure in otherwise healthy young people, a new study has found. The findings highlight the need for caution when consuming the sweet black treat.
Black licorice is one of those divisive foods; you either love the taste or you hate it. It’s made from the root of the Glycyrrhiza glabra plant, which has been used medicinally for centuries to treat various conditions such as lung, liver, circulatory, and kidney diseases.
Studies have found that licorice may have some health benefits. However, studies have also shown that the glycyrrhizic acid (GA) found in licorice root can elevate blood pressure, prompting the European Union and the World Health Organization to suggest that daily GA consumption be restricted to 100 mg or less. Researchers at Linköping University in Sweden decided to investigate whether even that ‘safe limit’ was bad for health.
They recruited 28 healthy participants aged 18 to 30 and randomized them into an intervention or control group. For two weeks, the intervention group ate 3.3 g of sweet licorice pastilles containing 100 mg of GA a day, while the control group ate vegan salty licorice candies with no GA. After a two-week ‘washout period,’ the intervention group became the control group, and vice versa. Participants were asked to abstain from eating licorice for at least four weeks before the study.
Blood pressure measurements were taken at baseline and over the course of participants’ engagement in the study. Blood samples were taken to measure sodium, potassium, lipids and creatinine, which shows how the kidneys are functioning, and two hormones that regulate fluid balance and blood pressure: renin and aldosterone.
The kidney’s adrenal glands produce aldosterone, which stimulates the kidneys' retention of sodium (salt) and the elimination of potassium. The kidneys also produce renin, which controls the hormone angiotensin. When there’s a drop in blood pressure or sodium concentration, renin is released, converting angiotensin into an enzyme that constricts the blood vessels and stimulates aldosterone production, increasing blood pressure and returning sodium and potassium levels to normal.
“In the study, we found that a daily intake of licorice containing 100 mg glycyrrhizic acid raised blood pressure in young, healthy people,” said Peder af Geijerstam, doctoral student at the University’s Department of Health, Medicine and Caring Sciences and the study’s lead and corresponding author. “This hasn’t previously been shown for such small amounts of licorice.”
When the participants ate licorice containing GA, their blood pressure increased by an average of 3.1 millimeters of mercury (mmHg). The researchers also found that renin and aldosterone levels decreased when licorice was consumed. The study participants who were most sensitive to the effects of licorice, based on the observed reduction in renin and aldosterone, gained weight, suggesting an increase in fluid in the body. This group also had higher levels of N-terminal pro-brain natriuretic peptide (NT-proBNP), a protein that the heart secretes when it needs to work harder.
“Our results give reason to be more cautious when it comes to recommendations and labeling for food containing licorice,” said study co-author Fredrik Nyström.
Herein lies the problem. Licorice root or licorice root extract is most likely to be found in dietary supplements to treat things like digestive problems and menopausal symptoms. In the US, the labels on these products may not specify the amount of GA they contain because although licorice is an FDA-approved food supplement, it’s not subject to precise regulation.
However, Americans who enjoy eating the sweet black treat can relax (mostly), as many ‘licorice’ products don’t contain licorice at all. Often anise oil, which smells and tastes like licorice but is GA-free, is used as flavoring. Nonetheless, to be on the safe side, keep your licorice binging to a minimum. The FDA recommends that people over 40 eat no more than two ounces (57 g) a day for two weeks; anything more than that can be problematic.
The study was published in The American Journal of Clinical Nutrition.
Source: Linköping University
