Should you have a banana with your liquorice? It might be a good idea and here we explain why. But first let’s start with the liquorice, and we are talking about the real stuff with the characteristic liquorice taste provided by glycyrrhizin and not sweets flavoured with aniseed or other similar flavourings.
Liquorice is the common name given to a flowering plant (Glycyrrhiza glabra) that grows in parts of Asia and Europe. The root of the liquorice plant is the source of a sweet, aromatic compound called glycyrrhizin, which is used as a flavouring in confectionery and drinks. It is over 50 times sweeter than succros. The root itself may also be used as a dietary supplement with claimed health benefits like anti inflammatory activities and respiratory health support.
Liquorice consumption considered safe
For most of us, the liquorice found in food is generally considered safe to eat and safe when consumed as a medicine for short periods of time. However, when taken in large amounts over an extended period, it may cause potassium levels in the body to fall and this may impact your blood pressure. Some people may be particularly sensitive to these effects, such as those with heart disease, kidney disease and high blood pressure. Daily consumption of 50 g or more of liquorice candy for as little as two weeks may increase blood pressure by a small amount. This in turn can trigger abnormal heart rhythms, oedema (swelling), lethargy, and congestive heart failure in some people.
The component glycyrrhizin is responsible for many of these side effects. Although the amount of glycyrrhizin varies depending on the manufacturer of the confectionary and country preferences, a recent Danish study established a typical mean content of around 2 mg/g. Safe intakes recommended by the European Union and the World Health Organization (WHO) are specified as up to 100 mg glycyrrhizin a day, equivalent to about 50 g of confectionary. The US FDA allows soft candy to contain a maximum of 3.1% of glycyrrhizin so a 100 mg limit would be reached after the consumption of only 4 g of confectionary.
Swedish study issues a warning
However, in a study published in 2024, Swedish researchers suggested that the safe limit for liquorice might need to be reconsidered after discovering a significant impact on blood pressure in healthy adults. The researchers recruited 28 healthy participants with an average age of 24 years. The study used a randomised crossover design, with participants either starting with a liquorice product containing 100 mg of glycyrrhizin or a control product. The first block consisted of a 1-week run-in, followed by the 2-week liquorice intervention, a 2-week washout, a 2-week control period and a further 2-week washout period. The second block reversed the sequence of 2-week periods.
The researchers observed significant increases in systolic blood pressure during the liquorice intervention period when compared to measurements in the control period. Blood pressure readings were found to show increases from day five, with a mean increase in systolic blood pressure of 3.1 mm Hg at day 14. In addition, renin and aldosterone were found to be suppressed during the liquorice intervention. Renin is a hormone made by the kidneys. It controls the production of aldosterone, a hormone made in the adrenal glands. Aldosterone helps manage blood pressure and maintain healthy levels of potassium and sodium in the body. These effects have not previously been demonstrated for such moderate amounts of daily intake of liquorice.
Thus the researchers indicated that liquorice seems to be a more potent substance than previously thought and that currently advised safe levels might need to be reconsidered.
And here is the saviour
So now we come to potential counter measures in case you cannot resist the temptation posed by liquorice candy. And bananas could be part of the answer.
Researchers at The George Institute of Global Health at Imperial College London analysed data from a five year monitoring study of 20,995 people in China where half of the participants had replaced the use of normal table salt in cooking with a “salt substitute” containing potassium-enriched salt. They found that a one gram increase in daily potassium intake lowered systolic blood pressure levels by 2 mm Hg on average.
As it happens consuming an extra gram of potassium is the equivalent of eating two medium-sized bananas, a cup of spinach or a large sweet potato. So eating bananas can actually be an effective way of reducing blood pressure similar to cutting down on salt intake.
A global collaboration of researchers from Australia, the US, Japan, South Africa and India have called for potassium to be added to international health guidelines, with just Chinese and European guidelines currently suggesting it as an effective way to reduce blood pressure.
So what are the lessons learned?
First up be careful with your liquorice intake. Maybe eating 50 g every day for two weeks is overdoing it a bit. And also we are talking about mean levels of glycyrrhizin in liquorice sweets while some products may have much higher levels.
On the other hand, it is possible to balance the potassium reducing effects of liquorice by consuming other potassium-rich foods. Bananas is a good choice as they have other beneficial health effects as well. And why not a cup of spinach on she side?
As always a balanced diet without excesses either way is the solution to a long and healthy life.
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