Roselle is an herbal supplement that is being studied for its blood pressure and cholesterol-lowering effects and for its anti-diabetic potential.
Roselle (Hibiscus sabdariffa) is a species of hibiscus plant that is traditionally steeped to make tea. It has long been used in African folk medicine to treat several conditions and diseases. Studies are underway to better understand the potential of this herb.
So far, roselle has been found to be rich in antioxidants, malic acid, anthocyanins, ascorbic acid and minerals. It is also rich in phenolic compounds which are known to have free radical scavenging abilities (1).
Roselle lowers high blood pressure. In recent years, researchers have found mounting evidence supporting roselle’s ability to treat hypertension. Uncontrolled hypertension (also known as high blood pressure) can lead to several serious complications such as heart attack, stroke, angina, kidney disease, vision loss and peripheral artery disease (2).
In 2017, the American College of Cardiology and the American Heart Association made changes to their blood pressure guidelines. Normal blood pressure is less than 120/80 mm Hg; elevated: systolic (top number) 120-129 and diastolic (bottom number) less than 80; hypertensive crisis: systolic over 180 and/or diastolic over 120 (3).
In a 2010 randomized, double-blind, placebo-controlled clinical trial, 65 pre- and mildly hypertensive adults (not taking blood pressure-lowering medications) took either 3 240-mL servings per day of brewed hibiscus tea or placebo beverage for six weeks.
At the end of the study period, hibiscus tea lowered systolic blood pressure compared with placebo. Diastolic blood pressure was also lower, although it did not differ from placebo.
These results suggest that daily consumption of hibiscus tea may prove to be an effective dietary change recommended for people with pre- and mild hypertension (4).
Similarly, a systemic review and meta-analysis of randomized controlled trials conducted in 2015, showed roselle’s significant effect in lowering both systolic and diastolic blood pressure (5).
Several other studies have shown equally promising results.
Roselle lowers cholesterol levels in patients with type 2 diabetes. In a 2009 comparative study, researchers evaluated the hypolipidemic (cholesterol lowering) effects of Hibiscus sabdariffa tea in patients with diabetes versus black tea.
Fifty-three patients were divided into two groups and instructed to drink either roselle tea or black tea, two times a day for one month.
At the end of the study period, those who drank the roselle tea had a significant decrease in total cholesterol, low density lipoprotein-cholesterol (LDL or “bad” cholesterol), triglycerides and Apo-B100 (a protein that plays a role in moving cholesterol around the body)6,7.
Another study showed that a daily dose of 100 mg Hibiscus sabdariffa extract powder (taken orally for one month) significantly reduced glucose and total cholesterol levels, increased high-density lipoprotein levels (HDL or “good” cholesterol), and an improved TAG/HDL-c ratio(a marker of insulin resistance) 8.
Not all studies, however, had such promising results. According to a 2013 issue of the Journal of Ethnopharmacology, a systemic review and meta-analysis did not support the efficacy of roselle in lowering serum lipids, when compared with placebo, black tea or diet (9).
More rigorously designed trials with larger sample sizes are therefore warranted to further examine this herb’s ability to lower cholesterol.
Roselle may improve liver health in obese people. Among other conditions, obesity is a risk factor for developing non-alcoholic fatty liver disease. In 2014, researches set out to examine the ability of Hibiscus sabdariffa extract to provide liver protection.
Participants with a body mass index of ≧ 27 were randomly divided into a Hibiscus sabdariffa extract group or control group for 3 months.
Results show that the extract reduced body weight, BMI, body fat, the waist-to-hip ratio and improved non-alcoholic fatty liver (10).
Roselle may help fight strains of bacteria. The results of a study published in a 2016 issue of the Journal of Intercultural Ethnopharmacolgy, showed that methanol extract of roselle contained effective antibacterial agents, and it was a competitor to gentamicin (an antibiotic used to treat bacterial infections) and greatly higher than penicillin which showed weak to no effect (11).
Further studies are needed to evaluate its ability to treat bacterial infections in humans.
The results of another study showed the potential use of Hibiscus extracts to prevent the growth of pathogens in foods and beverages (12).
Roselle has the potential to be an adjuvant therapy for diabetes. Using a type 2 diabetic rat model, researchers in 2011 found that treatment with Hibiscus sabdariffa polyphenolic extract reduced hyperglycemia (high blood sugar or glucose) and hyperinsulinemia (when the amount of insulin in the blood is higher than normal) 13.
With short-term, moderate use, roselle appears to be well tolerated. In one human study using roselle tea for 15 days, researchers failed to find evidence of toxicity. However, higher doses have been associated with toxicity in rats.
Roselle has also been shown to interact with other herbs and drugs. According to one study, using Hibiscus sabdariffa along with hydrochlorothiazide (a drug used to treat high blood pressure) causes several adverse effects, including a significant increase in the volume of urine excreted and a decrease in the pH of urine and the concentrations of several electrolytes (chemicals that must be in balance to help regulate important body functions) (14).
Further clinical studies are needed to determine the safest and most effective dosages, especially when it comes to roselle extracts.
Roselle (Hibiscus sabdariffa) is a species of hibiscus plant long used in African folk medicine for the treatment of several conditions. Clinical studies show that roselle is especially helpful in treating high blood pressure.
Roselle is rich in antioxidants, phenolic compounds, malic acid, anthocyanins, ascorbic acid and minerals. Early research shows its potential for lowering cholesterol and triglyceride levels in patients with type 2 diabetes as well as being an effective adjuvant therapy for type 2 diabetes. It also has the ability to improve non-alcoholic fatty liver and help to fight certain strains of bacteria.
Most of the current research, however, is limited to in vitro and animal studies. More studies are needed to determine how these benefits may apply to humans who drink hibiscus tea or take supplements.
While roselle appears to be safe when used in moderation and in the short term, higher doses have been associated with toxicity in rats.
It has also been shown to interact with certain herbs and drugs.