The leaf of the olive tree has become a popular immune supplement to prevent and treat colds, flu, and other infections, but it does even more. Studies show that olive leaf reduces the most common risk factors for heart disease, diabetes, and premature aging, a combination of symptoms described as metabolic syndrome. Such risk factors include elevated blood pressure, triglycerides, and blood sugar; unhealthy cholesterol; insulin resistance; and belly fat.
How can one leaf do so much? As with many plants, science has yet to identify all of its constituents, but test-tube, animal, and human studies have shown that some of the components found in olive leaf have strong antioxidant, anti-inflammatory, antimicrobial, and antiviral properties. Oleuropein, which is partially responsible for the pungent, bitter taste of extra virgin olive oil, is considered to be a key substance.
Most of the research has focused on olive oil, because it's a staple in the Mediterranean diet that is associated with low levels of age-related diseases and a longer life. Initially, the benefits of the oil were attributed to the characteristics of its fat, but other plant oils with similar types of fat are ineffective in improving health.
More recently, scientists have realized that compounds other than fat, such as oleuropein, are at least partially responsible for the healthy qualities found in olive oil. Oleuropein is a polyphenol, a beneficial class of nutrients in fruits and vegetables. Olive leaf supplements provide these nutrients in a concentrated form, without the fat.
Olive leaf has been used therapeutically in Mediterranean regions since the days of ancient Egypt. But in this country, interest was sparked about 20 years ago when an article in the Townsend Letter for Doctors and Patients called the supplement "nature's antibiotic," and some integrative physicians began using it to treat bacterial, viral, and fungal infections.
Since then, there haven't been any published human studies of olive leaf's immune-enhancing benefits. However, in addition to anecdotal evidence, unpublished research with 500 patients at a clinic in Budapest, Hungary, found that it was very effective in treating respiratory tract infections, dental infections, viral conditions such as herpes, and skin infections.
Minimizing Metabolic Syndrome
"There is enough evidence to suggest that this is a really useful, non-toxic, and safe addition to our health care for a condition that, according to the authorities, affects some 30 percent of Americans," says David Winston, RH (AHG), a registered herbalist, founding and professional member of the American Herbalists Guild, and author of Adaptogens: Herbs for Strength, Stamina and Stress Relief. But the numbers may be much higher, he adds. In his practice, between 50 and 60 percent of patients suffer from metabolic syndrome.
In studies, these are some of the results produced by olive leaf supplements:
- Lowered blood pressure as effectively as the drug Captopril, and lowered triglycerides (which the drug did not do), in a study published in Phytomedicine.
- Significantly improved levels of fasting blood sugar and insulin among 79 people with type 2 diabetes in a study published in the Journal of Medicinal Food.
- Improved insulin sensitivity by 15 percent and significantly reduced the risk for metabolic syndrome among 46 middle-aged men in a study published in PLoS One (Public Library of Science).
- Lowered blood pressure and harmful LDL cholesterol in a study that was published in Phytotherapy Research.
For people who are relatively healthy, Winston sees olive leaf as being particularly beneficial for the following groups: those with mildly or moderately elevated blood pressure, or blood pressure that creeps up a bit higher year by year; for those who are obese or have a belly (indicates risk for metabolic syndrome); or anyone with a family history of atherosclerosis. "Olive leaf," he says, "seems to be one thing that could potentially help people to live significantly healthier and hopefully longer, better lives."
Olive You-Cooking with Olives
Chopped and combined with capers and sun-dried tomatoes; scattered atop pan-seared sea bass; or roasted with blood oranges, garlic and rosemary, few foods are the culinary equal of olives. All olives are the fruit of the Olea europaea tree, but they vary depending on when the fruit is picked. Some to try:
Manzanilla olives. These are the pimento-stuffed green versions in glass jars on supermarket shelves. More upscale versions are stuffed with blanched almonds, bits of blue cheese, slivers of garlic, rolled anchovies, or thin slices of habanera peppers. The Manzanilla is medium-sized, plump and tender, with smoky, almond undertones. Love ‘em: Chop Manzanilla olives, combine with capers, olive oil, minced garlic and parsley, and serve on baguette slices; add chopped Manzanilla olives, minced red peppers, and fresh oregano leaves to scallops sautéed in garlic and olive oil.
Cerignola olives. Impressively large, with a firm, meaty flesh and taut skin, these are equally popular and delectable in the unripe green or fully ripened black versions. Green Cerignolas have a fresh, light, fruity flavor, while the black ones are sweet and buttery. Both are worth adoring. Love ‘em: Add quartered green Cerignolas, chopped dried apricots, chickpeas, and minced parsley to couscous; add chopped black Cerignolas to sautéed asparagus, radicchio, fennel and fresh thyme leaves.
Kalamata olives. These are best known for their role in Greek cuisine, especially as a key player in Greek salads. Kalamatas have a purplish tint, plump, juicy flesh and a winey bite. Love ‘em: Combine whole Kalamatas with crushed garlic cloves, olive oil, coarse sea salt, and chopped rosemary leaves, and roast until sizzling; toss halved Kalamata olives, chopped roasted tomatoes, minced basil leaves, and grated Asiago cheese with hot bow-tie pasta. -Lisa Turner
How to Benefit
In studies that tested olive leaf's effects on blood pressure, blood sugar, insulin resistance, cholesterol, and triglycerides, 500 mg twice daily, or 1,000 mg once daily have been effective dosages, using a standardized extract with 16 percent oleuropein. For immune enhancement or treatment, follow product directions.
Olive leaf is available in capsules, tinctures, and teas; a liquid olive leaf complex and throat spray (Barlean's); and in homeopathic olive leaf sprays (Seagate).
Olive Leaf Complex helps fight colds, flu, and infection with the antimicrobial, antiviral, and antibacterial power of freshly pressed and bottled olive leaves.
Sainthood HerbsHeart & LDL
includes a blend of olive leaf extract, plus turmeric and other protective herbs that work synergistically to help keep cholesterol levels in check.
Olive Leaf Homeopathic Nasal Spray features olive leaves, harvested and processed at their maximum potency and antioxidant levels, for quick relief of cold and sinus irritation.
In tests of antioxidant potential, this is how one olive leaf supplement (Barlean's Olive Leaf Complex) compared to superfruit juices:
- 28x noni juice
- 9x mangosteen juice
- 8x açai juice
- 6x goji juice
Better Nutrition contributing editor, Vera Tweed is the former editor in chief of GreatLife magazine and the author of numerous books, including Hormone Harmony and the User's Guide to Carnitine and Acetyl-L-Carnitine.