The randomised, double-blind placebo controlled, cross over trial, investigated the absorption and metabolism of polyphenols from olive leaf extract (OLE), in addition to measuring the physiological outcomes, “in order to build a greater understanding of the ‘cause-and-effect’ relationship between OLE intake and potential biological effects.”
Led by researchers from the University of Reading, and backed by funding from Comvita and an R&D Project Grant from the New Zealand government’s business innovation agency, the study is said to provide “the first evidence that OLE positively modulates vascular function and IL-8 production in vivo, adding to growing evidence that olive phenolics could be beneficial for health.”
Professor J.P.E Spencer from the University of Reading, corresponding author of the study which is published in the British Journal of Nutrition, commented that the research was important to explore links between absorbed OLE components and positive changes in vascular function and pro-inflammatory markers – adding that longer term epidemiological studies are needed to establish ‘definitive conclusions.’
Brett Hewlett, CEO of Comvita added that a longer and larger study of OLE targeting cardiovascular health has been conducted, with publication expected in 2015.
Indeed, Rashda Ali, UK managing director of Comvita Ltd told NutraIngredients that the follow up study, carried out by the University of Reading and the University of Auckland, is investigating the effects of the company’s olive leaf extract on a wider range of cardiovascular markers in a trial with a larger number of participants.
She added that the firm are currently building a bank of evidence for the product with a long term aim of achieving an EFSA approved health claim for the olive leaf extract, but noted that it is ‘too early to say’ whether such a claim would relate to the cardiovascular risks being currently studied.
“Additional trials are being considered on CVD and other conditions,” said Hewlett.
Study details
The randomised, double-blind, placebo-controlled, cross-over, acute intervention trial was conducted with eighteen healthy volunteers (nine male, nine female), who consumed either Comvita’s OLE (51 mg oleuropein; 10 mg hydroxytyrosol HT), or a matched control (separated by a 4-week wash out) on a single occasion.
The team measured vascular function by digital volume pulse (DVP), while blood collected at baseline, 1, 3 and 6 hours was cultured for 24 h in the presence of lipopolysaccharide in order to investigate effects on cytokine production. Urine was also analysed for phenolic metabolites by HPLC.
The team reported that DVP-stiffness index and ex vivo IL-8 production were significantly reduced after consumption of OLE compared to the control.
“These effects were accompanied by the excretion of several phenolic metabolites, namely hydroxytyrosol and oleuropein derivatives, which peaked in urine after 8–24 h,” wrote the team.
Source: British Journal of Nutrition
Published online ahead of print, doi: 10.1017/S0007114515001269
“Secoiridoids delivered as olive leaf extract induce acute improvements in human vascular function and reduction of an inflammatory cytokine: a randomised, double-blind, placebo-controlled, cross-over trial”
Authors: Stacey Lockyer, et al