Educational information, not medical advice — ask your doctor or midwife.
Flor de Jamaica is the dried red flower cup of Hibiscus sabdariffa, a plant also called roselle. In Latin America it is steeped in water to make a tart, deep red drink. It is sold as a food, a tea and a supplement.
People drink it for pleasure and thirst. It is also taken as a folk aid for blood pressure, digestion and fluid retention.
Here is the short verdict on the evidence. Small human trials point to a modest drop in blood pressure over a few weeks. Other claimed uses rest mainly on tradition and lab work.
Long use in a culture is not proof that something works, and it is not proof that it is safe. That applies here, even though the drink itself is an everyday food.
No one has shown exactly how hibiscus affects blood pressure in people. Most of the detail comes from lab and animal work.
In test tubes, hibiscus extracts block an enzyme called ACE. That enzyme helps control how tight blood vessels are. Some blood pressure drugs act on the same target, but it is not proven that a cup of tea does this in your body.
In animals, hibiscus acts like a mild water pill (diuretic). It helps the body shed salt and water. Whether this explains the small drop seen in human trials is still unclear.
The red colour comes from anthocyanins, plant pigments that mop up damaging molecules in lab tests. Lab antioxidant activity does not always mean a benefit in people.
In cell and animal studies, hibiscus extracts also relax blood vessel walls and slow some fat-handling enzymes. These are early findings. They have not been confirmed as the reason for any effect in humans.
Dried calyces, loose or in tea bags, are the most common form.
Agua de Jamaica is the cold, often sweetened drink made from steeped calyces.
Hot tea from the same dried flowers is also widely drunk.
Capsules and tablets hold powdered calyx or a concentrated extract.
Liquid extracts, syrups, jams, candies and dried sweet snacks are sold in many markets.
Hibiscus also turns up as a natural food colour and in blended herbal teas.
Two points are worth noting before you buy. Blends may contain other herbs, so read the label. A concentrated capsule is far stronger than a cup of tea.
Hibiscus sabdariffa came from West Africa and spread through trade and the slave trade to the Caribbean and the Americas. In Mexico it became agua de Jamaica, a standard agua fresca sold in markets and homes.
Folk healers in Mexico and Central America used the tea as a cooling drink in hot weather. It was also given for mild swelling, for sluggish digestion and later for high blood pressure.
The plant has a long record outside Latin America too. In Egypt and Sudan it was drunk as karkade, and in the Caribbean as sorrel at Christmas. These records describe custom, not tested medical results.
Stop using it and speak to a doctor or pharmacist if any of these happen.
You feel dizzy, faint or unusually weak after drinking it. Your blood pressure readings drop lower than your doctor wants. You get shaky, sweaty or confused, which can mean low blood sugar.
Get urgent medical help for swelling of the lips, face or throat, a rash with trouble breathing, yellowing of the skin or eyes, or dark urine with belly pain.
Also see your doctor if you are using hibiscus instead of prescribed blood pressure treatment. That swap is not safe to make on your own.
In the United States, hibiscus is an ordinary food and tea ingredient, and is also sold as a dietary supplement. It is not approved as a medicine. In the UK, EU, Canada and Mexico it is likewise treated as a food or a supplement, not a drug.
Evidence grades and traditional-use labels are explained in our methodology. Nothing here is medical advice.
What it is typically used for, usual dose, cautions, and the study behind it where real trial data exists.
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