These findings came from a 'Twins' trial, in which different treatments were given to identical twins.
By doing this, researchers could increase the power of their data by eliminating some of the uncertainties caused by genetic variations between individual people.
The research is published in the latest edition of Phytotherapy Research.
Hypertension is one of the most common and important disease risk factors imposed by the modern lifestyle. Many people would therefore benefit from finding ways of reducing blood pressure. Experiments in rats had previously indicated that olive leaf extract could be one way of achieving this goal.
To test this in humans, researchers from Switzerland and Germany conducted a pilot trial with 20 identical (monozygotic) twin pairs who had an increased blood pressure.
ndividuals were either given placebo capsules or capsules containing doses of 500mg or 1000mg of olive leaf extract EFLA943.
Pairs of twins were assigned to different treatments. After the subjects had taken the extract for eight weeks researchers measured blood pressures as well as collecting data about aspects of life-style.
"The study confirmed that olive leaf extract EFLA943 has antihypertensive properties in humans," says one of the co-authors, Cem Aydogan, General Manager, Frutarom Health.
"This works showed that taking a 1000mg dose has substantial effects in people with borderline hypertension," says Aydogan.