A team of scientists from Nigeria and Britain studying the effects of consumption of hibiscus tea on cardiovascular health has found significant increase in ‘flow-mediated dilation’ of the brachial artery after participants consumed hibiscus tea after a meal. Flow-mediated dilation refers to the widening of an artery when blood flow increases in that artery, considered a gold standard to measure vascular endothelial function.
The results led the researchers, who came from Bayero University in Zaria and University of Reading in the UK to conclude that consuming the extract of Hibiscus sabdariffa flowers after a meal improved vascular function and “may be a useful dietary strategy to reduce endothelial dysfunction and cardiovascular disease risk, although this requires confirmation.”
However the study did not find any other significant changes in other markers of cardiovascular disease risk reduction (besides widening of the brachial artery), such as changes of systolic and diastolic blood pressure (which was the primary outcome measure) or changes in arterial stiffness.
Health benefits of anthocyanin-rich hibiscus calyces have been studied before, such as one in 2010 by Tufts University researchers in the United States, which linked it to reduced blood pressure. However, no study has looked at the acute impact of consuming hibiscus calyces.
Because of this, it is difficult to compare directly with other hibiscus extract human studies, though “acute consumption of anthocyanins-rich blueberries showed similar effects,” they argued.
The health study involved 22 men who were recruited in Reading, United Kingdom. The participants had a cardiovascular disease risk between 1% and 10%, measured using a QRISK2 calculator.
A special hibiscus drink was prepared for the study using a method which the researchers described as “the usual method employed by habitual tea consumers,” where 30 g dried hibiscus calyces in tea bags were steeped in 1 litre of low nitrate water for 10 minutes.
The study was a randomized, controlled, single-blinded crossover study. Blood pressure and flow mediated dilation were measured at the beginning of the study.
Participants were assigned to consume a glass of hibiscus or plain water with a high fat meal (buttered croissants with butter and honey) followed by a high fat meal of cheese sandwiches, a bag of slated chips, and shortbread biscuit fingers.
Blood samples and other cardiovascular measurements were collected at two hours and four hours after the meal. After a two-week wash-out period, the participants returned to follow the same protocol but with a different drink.
Published online ahead of print, doi:10.3390/nu11020341
“Acute Effects of Hibiscus Sabdariffa Calyces on Postprandial Blood Pressure, Vascular Function, Blood Lipids, Biomarkers of Insulin Resistance and Inflammation in Humans
Authors: Salisu M. Abubakar, et al.