More precisely, they found a significant increase in ‘flow-mediated dilation’ of the brachial artery after participants ingested the hibiscus drink after a meal, referring 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, affiliated with the University of Reading in the UK and Bayero University in Nigeria, 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.”
These results were published recently in the journal Nutrients.
A novel study
Aside from a widening of the brachial artery, they found no significant changes in other markers of cardiovascular disease risk reduction, such as changes of systolic and diastolic blood pressure (which was the primary outcome measure) or changes in arterial stiffness.
However, the authors added that their study was novel. Though the health benefits of anthocyanin-rich hibiscus calyces has been studied before, such as one 2010 study by Tufts University researchers that linked it to reduced blood pressure, none have 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.
Hibiscus beverages are becoming more prevalent in the US. A report by Google in 2017 mentioned that hibiscus was a top beverage search.
More recently, flavors company Firmenich named Hibiscus its 2019 Flavor of the Year. Firmenich cited Mintel’s Global New Product Development data, which revealed that worldwide use of hibiscus in food and beverage in new product launches has increased nearly 300% since 2012.
Twenty-two men recruited in Reading, UK, completed the study. All 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.