Study Shows Traditional Drink Lowers Blood Pressure

For generations, people across Africa, Mexico, and the Caribbean have brewed a deep red tea from the hibiscus flower to help manage their health. In Egypt, the drink is called karkade. In West Africa, it’s bissap. Mexican households know it as agua de jamaica, and across the Caribbean the same red brew becomes sorrel at Christmas. A new scientific review suggests these traditions were onto something real.

Researchers published an umbrella review in Complementary Therapies in Medicine early in 2025. Rather than running a fresh experiment, they combined results from thousands of participants across dozens of previous studies on hibiscus sabdariffa, the flower behind these drinks. The goal was to settle years of conflicting headlines about whether the tea actually works for blood pressure.

Earlier hibiscus trials had produced a frustrating mix of strong results and shrugs. Small sample sizes and inconsistent amounts made the picture blurry. Pooling everything together let a real signal separate from the noise for the first time.

Blood pressure numbers landed close to medication territory

Hibiscus lowered both systolic and diastolic blood pressure across the pooled data. The drop scaled with how much people consumed.

The team compared the effect directly against certain pressure medications and found the gap smaller than most people would expect from a beverage. Few food-based interventions get anywhere close to that comparison.

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The benefit also grew with time. People who kept drinking the tea for six weeks or longer saw stronger results than those who tried it briefly. Older adults showed some of the largest improvements of anyone studied.

The paper does not fully answer whether the effect rivals medication after several weeks over years of daily use, though the trajectory suggests more research is warranted.

The heart was not the only system that responded

Cholesterol moved in the right direction too. Total cholesterol and LDL cholesterol decreased across the pooled trials, while HDL cholesterol increased modestly. Fasting blood sugar improved alongside those changes, which suggests one flower was touching several connected systems at once, rather than fixing a single number in isolation.

The authors pointed to the deep red anthocyanins in the plant as the likely thread connecting these results. Those same antioxidant compounds give the tea its distinctive color. Their effects on inflammation and oxidative stress may explain why so many unrelated cultures noticed a heart benefit without ever knowing the underlying chemistry.

Turning centuries of tradition into a daily habit

Three cups of brewed tea daily, steeped for at least five minutes, matched the range tied to the strongest results in this analysis. A standard tea bag holds roughly 1 to 2 grams of dried flower, so three cups lands squarely in that window without any guesswork involved. Cold brewing works as an alternative for anyone who finds hot tea unappealing in summer, though the process takes several hours to extract a similar concentration of anthocyanins.

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Drinking the tea between meals rather than alongside them appears to support steadier absorption, based on patterns across the pooled trials.

One caution matters here.

Anyone already taking medication for the condition should speak with a doctor before adding the drink daily, since the two together can occasionally push numbers lower than intended.

Karkade, bissap, jamaica, and sorrel never needed a peer-reviewed journal to know something was working. The pooled data from this paper essentially confirms what generations of home cooks already trusted, using tools those cooks never had access to. That kind of convergence between old tradition and new evidence is rare enough to take seriously.