Hibiscus and blood pressure: does drinking it hot or cold matter?

Which hibiscus are we discussing?

The plant investigated in these studies is known as Hibiscus sabdariffa, or roselle. Its fleshy calyces are used to flavour and colour drinks. A calyx is not simply another name for flower petals, and ornamental plants called hibiscus should not automatically be treated as the same food plant. North Carolina State University's plant reference now lists roselle as Sabdariffa gossypiifolia, noting its former name. Botanical reference

An ordinary infusion and a concentrated extract are not interchangeable. Plant quantity, constituent concentration and extraction method differ, so a finding must remain linked to the preparation actually tested.

What did the human trial find?

A randomized trial published in 2010 involved 65 adults with mildly elevated blood pressure who were not taking blood-pressure-lowering medication. After six weeks, average systolic pressure fell by 7.2 mmHg in the hibiscus group and 1.3 mmHg in the placebo-drink group. The between-group difference in diastolic pressure change was not statistically significant. This is encouraging evidence under the study conditions, not a guaranteed response for every person or proof that medication can be replaced. McKay and colleagues

Preparation temperature is not serving temperature

A 2022 study compared hot-water and cold-water extracts in laboratory tests and rats with experimentally induced hypertension. Both extracts lowered systolic pressure in that animal model. The researchers did not compare people drinking otherwise identical hot and cold beverages. Their findings therefore cannot directly answer that human question. Salem and colleagues

Common claims: what does the evidence say?

“Hibiscus raises blood pressure”

Assessment: the cited studies do not support this generalization. The human trial pointed towards lower systolic pressure, not higher pressure. A group average nevertheless does not describe every individual's response or every product and health condition.

“Hibiscus lowers pressure only when cold”

Assessment: a special requirement for cold drinking temperature is unproven here. The human trial did not isolate serving temperature, and both extraction methods produced a lowering effect in rats. Evidence of a possible benefit does not establish coldness as its cause or prerequisite.

“Hot hibiscus raises pressure”

Assessment: unsupported by the comparison reviewed. The hot-water extract did not raise pressure in the animal experiment. However, this is not definitive evidence about all drinking conditions in humans. These references contain no direct human comparison isolating serving temperature alone.

Safety and practical limits

Do not use this article to change prescribed treatment or replace pressure monitoring with a drink. People taking antihypertensive medication, or experiencing low pressure, should discuss regular therapeutic use with a clinician or pharmacist. The human trial excluded medication users and does not establish the safety of combining treatments.

Its results also cannot be generalized to pregnancy, breastfeeding or children. These are limitations of the evidence presented, not a claim that every culinary use is harmful.

Takeaway

Human evidence suggests a systolic-pressure reduction in specific circumstances. The claim that heating alone reverses the effect from lowering to raising pressure is not supported by these studies. Keep extraction temperature, drinking temperature and personal treatment decisions separate.

Notice: This is educational information, not a diagnosis or prescription. Conclusions may change as research develops. Do not start treatment or alter medication on this article alone.