A supplement containing olive leaf extract may help lower blood pressure and cholesterol in people on the brink of developing high blood pressure, a new study suggests.

The leaves of the olive tree have been used for medicinal purposes since ancient times, and modern lab research suggests that olive leaf extracts have antibacterial, anti-inflammatory and antioxidant actions. There is also evidence that the extracts have properties that could lower blood pressure.

The current study, published in the journal Phytotherapy Research, included 20 sets of identical twins with "borderline" hypertension -- blood pressure that is above the optimal level of 120/80, but below the cutoff of 140/90 used to diagnose high blood pressure.

One member of each twin pair was given tablets containing olive leaf extract, while the other received no supplements but did get lifestyle advice on lowering blood pressure -- the standard approach to managing borderline hypertension.

Half of the supplement users took 500 mg of olive leaf extract per day, and the other half took 1,000 mg.

After eight weeks, the study found, supplement users on the higher dose showed a substantial dip in their blood pressure overall -- from an average of 137/80 to 126/76. They also saw their average level of "bad" LDL cholesterol fall.

In contrast, the twins who received no supplements showed no significant change in their blood pressure and a smaller improvement in cholesterol, according to the researchers, led by Tania Perrinjaquet-Moccetti, a molecular biologist with Frutarom Switzerland Ltd. in Wadenswil.

The company makes the olive leaf extract used in the study, a product called Benolea. 

The benefits seen in this study can be attributed to the various "bioactive components" of the olive leaf, Perrinjaquet-Moccetti told Reuters Health. The most significant of these, she noted, is a compound called oleuropein.

Research shows that oleuropein acts as an antioxidant and can help relax and dilate the blood vessels.

However, Perrinjaquet-Moccetti added, no single ingredient of the olive leaf extract accounts for its blood pressure benefits.

Olive leaf extracts are available over the counter, but people with high blood pressure, or any medical condition, are generally advised to consult their doctor before self-prescribing a supplement.

Perrinjaquet-Moccetti said it "would be wise" for patients to mention any supplement use to their doctor, especially if they are taking any medications. Herbal supplements have the potential to interact with drugs, which could interfere with the medication's effectiveness or create side effects.

SOURCE: Phytotherapy Research, September 2008.