Some tea and alcohol products also contain liquorice. A fresh PhD research study from Tampere University has found that enjoying a daily helping of liquorice candy can cause blood pressure levels to rise to the same extent that blood pressure medications normally lower them.
"People who already have high blood pressure should avoid any products that contain liquorice extract," says Elina Hautamäki , the author of the dissertation.
Commercial liquorice is obtained mainly from the dried root of the Glycyrrhiza glabra plant. Liquorice extract is commonly used as a sweetener or flavouring agent in candy and confectioneries, chewing gum, drinks, herbal teas, chewing tobacco, herbal medicines, and medicinal products like cough syrup.
The study population in Hautamäki’s study was asked to eat 120-300 grams of liquorice candy daily for two weeks. During this time, the peripheral and central blood pressure of the test group increased, as did arterial resistance and stiffness.
Liquorice causes blood pressure levels to rise, due to sodium and water retention. Differing sensitivities make it hard to define a safe level
Hautamäki says the level of liquorice extract varies from one product to another, and this information is normally not stated by the packaging.
She says people’s different sensitivities to liquorice make it hard to come up with safe ingestion levels that would apply across the board.
"If you have normal blood pressure, you can enjoy liquorice products in moderation, from time to time," she says.
The impact that liquorice has on blood pressure levels normally lasts for weeks. Hautamäki says this is why it is very important to determine whether patients with blood pressure issues have ingested any liquorice products in the recent weeks when making diagnoses.
Hautamäki’s doctoral defence will take place at the Tampere University department for internal medicine on 29 March.
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