Cem Aydogan of Frutarom Health said that the findings came from a "twins' trial," in which different treatments were given to identical twins.

The researchers conducted a pilot trial with 20 identical twin pairs who had an increased blood pressure, or mild hypertension. Individuals were either given placebo capsules or capsules containing doses of 500 mg or 1,000 mg of olive leaf extract EFLA 943. 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 lifestyle.

"The study confirmed that olive leaf extract EFLA 943 has anti-hypertensive properties in humans," Aydogan said in a statement. "This works showed that taking a 1000 mg dose has substantial effects in people with borderline hypertension."

The research is published in the latest edition of Phytotherapy Research.