Can olive leaf extract cure high blood pressure?
BACKGROUND
The olive tree is a traditional symbol of abundance. Its cultivation is economically significant in the Mediterranean region, with attention focused on olives and olive oil. At the same time, uses are being sought for other parts of the olive tree. During pruning and harvesting, many olive leaves and small branches are collected. Given the health benefits of olive oil, interest has turned to the potential benefits of olive leaves. Herbal teas have been made from the leaves, and extracts used to produce capsules. The most promising area to date has been in the use of olive leaf extracts for high blood pressure.
EVIDENCE FROM STUDIES
Olive products contain antioxidants which are believed to underlie their beneficial effects. Olive leaves have the highest antioxidant levels among the various parts of the olive tree. This activity is due to polyphenols, the most abundant of which is called oleuropein. Some products are now standardised to contain a certain amount of oleuropein. Normal metabolism produces compounds that cause oxidation. Overproduction of oxidants, or a lack of the body’s natural antioxidants, has been connected with increased risk of heart disease and other chronic illnesses. Antioxidant supplements are promoted as a way to reduce this risk. Oleuropein specifically protects heart tissue from oxidation.
The first human trial was an uncontrolled study in which 30 patients with high blood pressure were given olive leaf extract for three months. At that point, all patients had significantly reduced blood pressure. The lack of a control group is a significant limitation with this study, but it prompted more research. Several studies have been done in animals suggesting olive leaf extracts may be beneficial for heart disease.
The second study in humans was published in 2009. It involved pairs of twins who had recently been diagnosed with mildly-elevated high blood pressure. One twin was given olive leaf exact and the other information on diet and exercise. Another part of the study compared different doses of the olive leaf extract. After eight weeks, the olive leaf extract led to significantly lower blood pressure, with the higher dose having a greater effect.
The most recent study, published earlier this year, was a randomised controlled study. It involved about 200 patients with high blood pressure that had not improved with dietary changes. Patients were randomly assigned to either olive leaf extract or captopril, a medication for high blood pressure. Blood pressure was reduced by the same amount in each group. The olive leaf group also had a beneficial lowering of cholesterol levels, which wasn’t seen in the captopril group.
PROBLEMATIC ASPECTS
Olive leaf extract and other olive products are widely used without problems. However, the most recent study kept a detailed record of all adverse effects. A small percentage of people had muscle discomfort or headaches while taking the leaf extract. All were mild cases which had resolved themselves before the study ended.
RECOMMENDATIONS
Olive leaves have a long history of medicinal use, although they have been used for many different ailments. Given recent attention to olive oil in heart-healthy diets, research is beginning to focus on olive leaf extracts. The studies conducted to date have consistently shown beneficial reductions in blood pressure.
However, three small studies is a relatively small amount of evidence and more research is needed. The studies have been of short duration, while blood pressure management in a long-term issue. Olive leaf extracts may have a role in managing blood pressure along with diet, exercise and other lifestyle factors. Given the potentially serious consequences of high blood pressure, medications should not be adjusted without consulting your doctor.
Dónal OMathúna has a PhD in pharmacy, researching herbal remedies, and an MA in bioethics, and is a senior lecturer in the school of nursing and human sciences, DCU
