Olive Leaf Extract: Benefits & Side Effects Of This Mediterranean-Diet-Approved Ingredient

Contributing Health & Nutrition Editor By Stephanie Eckelkamp
Contributing Health & Nutrition Editor
Stephanie Eckelkamp is a writer and editor who has been working for leading health publications for the past 10 years. She received her B.S. in journalism from Syracuse University with a minor in nutrition.
Expert review by Megan Fahey, M.S., R.D., C.D.N.

Megan Fahey, MS, RD, CDN is a Registered Dietitian, Functional Medicine Nutritionist and Registered Yoga Teacher. She holds her Masters of Science in Nutrition and Dietetics from Bastyr University, where she was trained to artfully blend eastern and western healing modalities.

Olive Oil

If you ask most doctors how to eat for optimal health and longevity, chances are they'll point you to a Mediterranean diet. For starters, it's light on processed foods, but researchers also believe that olive oil plays a major role in delivering its health benefits, thanks to one of its main compounds known as oleuropein.

Oleuropein is responsible for that slightly spicy, pungent flavor you'll encounter in a quality extra-virgin olive oil. But supplement manufacturers are able to produce something called olive leaf extract, which contains a stable, standardized form of oleuropein so you can reap the benefits (in concentrated form) without having to consume huge quantities of olive oil.

Here's your crash course on olive leaf extract, plus the benefits and potential side effects of the ingredient and how to choose the right supplement. This way, you won't have to chug your weight in olive oil to experience the health benefits.

So what is olive leaf extract?

The first known record of olive leaf comes from Ancient Egypt, where its antimicrobial oils were used to mummify kings. It has since been used extensively in traditional medicine to treat a variety of ailments and is still popular across many cultures today. In Japan, olive leaves are taken orally for stomach and intestinal diseases, while in Greece and the Canary Islands, a hot water extract of olive leaves is taken orally to treat high blood pressure. In Italy, people reach for a tincture of olive leaves to reduce fever, and in several countries, olive leaf extract has been used to treat malaria.

The most potent active compound in olive leaf extract is oleuropein, but the extract also contains high levels of phenolic and flavonoid compounds (such as luteolin, apigenin, rutin, hydroxytyrosol, verbascoside, and ligstroside), which work synergistically with oleuropein to enhance its natural activity.

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What are the health benefits?

In addition to major metabolic and cardiovascular perks, taking olive leaf extract has also been shown to provide antiviral, anticancer, and neuroprotective benefits. "Its bioactive compounds are not only antioxidant and anti-inflammatory, but they can lower blood pressure, improve blood glucose levels, reduce cholesterol levels, and improve lipid ratios," says integrative neurologist Ilene Ruhoy, M.D., Ph.D. "These actions are powerfully cardioprotective and can reduce the risk of diabetes, hypertension, heart attack, and stroke."

Here's a rundown of the most promising ways an oleuropein-rich olive leaf extract supplement may affect your health:

1. It lowers blood pressure, cholesterol, and triglycerides.

Numerous studies have shown that olive leaf extract significantly reduces blood pressure in people with hypertension or borderline hypertension—to the point that those who are already on blood-pressure-lowering medication should consult with their doctor before supplementing with the oil since their levels could potentially drop too low.

In fact, olive leaf extract may be just as effective as prescription blood pressure medication for some people. In this study, participants who took 500 mg of olive leaf extract twice a day for eight weeks experienced a comparable drop in blood pressure to those who took the medication Captopril.

Olive leaf extract is thought to lower blood pressure by acting as a calcium channel blocker, which relaxes and widens the blood vessels. In the same study, olive leaf extract also lowered triglyceride levels (i.e., levels of fat in the blood), while Captopril did not. This is important for heart health, as high triglyceride levels contribute to hardening of the arteries, or atherosclerosis, which increases the risk of heart attack and stroke.

Supplementing with olive leaf extract has also been found to lower total and LDL (bad) cholesterol in both animals and humans with high cholesterol. Researchers suspect that the polyphenols present in olive leaf extract, like oleuropein, decrease the activity of key cholesterol-regulatory enzymes, resulting in reduced cholesterol production.

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2. It helps fight cold and flu.

Olive leaf extract may be just the thing to help prevent or shorten your next flu. This research review suggests that olive leaf compounds interact with the protein of virus particles and reduce their ability to infect us. They also slow the replication of viruses known to cause colds, influenza, and lower respiratory infection.

Additionally, olive leaf extract has been shown to stimulate phagocytosis, the process by which cells called phagocytes engulf and destroy harmful foreign particles in our bodies like bacteria and viruses. Anecdotally, people have also found that gargling with olive leaf tea alleviates sore throats, possibly by decreasing inflammation

3. It holds promise as a natural herpes remedy.

Thanks to its potent antiviral properties, olive leaf extract may even help treat the herpes simplex type-1 virus (aka oral herpes, which causes sores around the mouth and lips). This study found that olive leaf extract exhibited a significant antiviral activity against HSV type-1 virus in the lab. If you have herpes and want a more natural approach to managing symptoms, talk to your doctor about alternatives like olive leaf extract before making the switch on your own.

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4. It's antibacterial, antifungal, and antiparasitic.

Olive leaf extract has an antimicrobial effect against bacteria and fungi, too. In this lab study, various bacteria and fungi were immersed in an olive leaf extract solution, and after three hours, the extract killed almost all of them, including dermatophytes, which cause skin, nail, and hair infections, and E. coli, which can cause severe diarrhea and candida.

Research also reveals that olive leaf extract is effective at slowing the progression of certain parasitic infections, which makes sense since people have been using olive leaf extract to help treat malaria since the 1800s.

5. It reduces inflammation and arthritis pain.

The polyphenols in olive leaf extract are antioxidant and anti-inflammatory. In fact, olive leaves and their extracts have long been used (orally and topically) throughout the Mediterranean to combat painful, inflamed joints, and arthritis. In this animal study, rats with osteoarthritis (OA) that were given olive leaf extract experienced a significant reduction in paw swelling, leading researchers to believe that it holds promise as a treatment for human OA too.

Other research suggests that olive leaf extract can attribute its anti-inflammatory properties to its ability to decrease the production of pro-inflammatory cytokines. Specifically, olive oil polyphenols have been shown to decrease the circulating concentrations of interleukin 6 (IL-6), a pro-inflammatory cytokine that stimulates inflammation in diseases like rheumatoid arthritis and cancer.

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6. It possesses potent anti-cancer properties.

Research shows that olive leaf polyphenols are anti-inflammatory and protect against DNA damage initiated by free radicals, which are characteristic of many types of cancer. Also, thanks to their structure, which is similar to estrogens, they're thought to interact with estrogen receptors and thus reduce the prevalence and progression of hormone-related cancers, like breast cancer.

Oleuropein, the main polyphenol in olive leaf extract, is thought to be responsible for the major anti-cancer, anti-tumor activity, and several experimental animal studies have found that oleuropein treatment prevents the development of skin and breast cancers. That said, evidence for the cancer-fighting effect of olive leaf extract in humans remains anecdotal, and clinical trials are needed to validate these claims.

7. It helps balance blood sugar and manage type 2 diabetes.

Olive leaf extract seems to help manage type 2 diabetes in several ways. One study tested the effects of olive leaf extract on rats and found that it slowed the digestion of starches into simple sugars. This, researchers speculate, may be why olive leaf extract supplementation helps stabilize blood sugar in humans. The same study found that human participants with type 2 diabetes who took 500 mg of olive leaf extract daily experienced a significant reduction in fasting insulin levels and hemoglobin A1c, a marker of long-term exposure to elevated blood sugar.

Some research even suggests that olive leaf extract may help counter the negative metabolic effects of a poor diet. In this animal study, rats fed a high-carb, high-fat diet developed the classic signs of metabolic syndrome: abdominal fat, high blood pressure, and poor blood sugar control. But when rats were fed this same poor diet along with olive leaf extract, nearly all of these abnormalities improved. Researchers say this strongly suggests that olive leaf extract polyphenols such as oleuropein reverse the chronic inflammation and oxidative stress that trigger these metabolic symptoms.

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8. It protects against Alzheimer's and cognitive decline.

The Mediterranean region consistently has low rates of dementia, and this might be thanks to olive leaf too. Research suggests that oleuropein, present in olive leaf extract, may be one of the most important neuroprotective polyphenols, with studies finding that it helps counteract the creation of amyloid plaque in the brain (which collects between neurons and disrupts cell function) that is characteristic of Alzheimer's disease.

Olive leaf extract offers other neuroprotective perks as well. In one animal study, pretreating gerbils with olive leaf extract before inducing them with a stroke significantly reduced the damage in their hippocampus, an area of the brain thought to be the center of emotion, memory, and the autonomic nervous system. Researchers speculate that this is due to olive leaf extract's potent antioxidative properties.

What are the side effects?

"Most people should be able to safely take olive leaf extract at appropriate doses," says Ruhoy. But there are a few key exceptions. Oleuropein, the active ingredient in olive leaf extract, may exacerbate low blood pressure in people whose blood pressure is already lower than average. It can also interact with prescription drugs that are designed to lower blood pressure or regulate diabetes. So, as is the case with all supplements, it's important to consult with your doctor before taking olive leaf extract in order to avoid interactions and side effects.

It's also recommended that you take olive leaf extract with food and split doses up throughout your day to avoid stomach irritation. Starting with a lower dose can also help minimize any potential side effects.

How to choose the right olive leaf extract supplement.

Olive leaf extract is available in both capsule and liquid form. "While some think the liquid formulations are more potent due to better absorption, which can be true, the capsules are more standardized for dosing that is effective," says Ruhoy.

For capsules, experts typically recommend 500 to 1,000 mg of olive leaf extract per day—a range that's been shown to deliver significant blood pressure and blood sugar benefits in human studies (however, even higher amounts seem to be well-tolerated). To ensure you're getting a potent product, look for capsules that are standardized to 18 to 25% oleuropein.

As with all supplements, look for one from a reputable brand that has been third-party verified to contain the appropriate ingredients in the correct quantities and is free of contaminants.

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