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Research is beginning to show that olive leaf extract may have several potential health benefits. These include lowering blood pressure, improving cholesterol, and reducing the risk of weight gain and type 2 diabetes. People in the Mediterranean region have long used olive tree leaves as part of their diet and in traditional medicines.
Olive leaves contain several key polyphenols, such as oleacein and oleuropein. Polyphenols occur naturally in plants, and research suggests that they may help protect against a range of conditions, such as heart disease and cancer. These polyphenols may underlie some of the potential health benefits of olive leaf extract.
Olive tree leaves contain oleuropein, which is a polyphenol that may help prevent weight gain. In a 2016 study, researchers orally administered oleuropein to rats with obesity that were consuming a high-cholesterol diet. After 8 weeks, the rats had a lower body weight, less fat tissue, and an improved metabolic profile.
Another study from 2014 found that oleuropein supplementation reduced body weight and weight gain in mice that were consuming a high-fat diet. These findings suggest that olive leaf extract containing oleuropein may have the potential to reduce weight gain and lower the risk of obesity.
However, further studies are necessary to confirm this possible health benefit in humans. Preliminary studies suggest that olive leaf extract may help improve cholesterol levels. In a 2015 study, rats ate either a high-cholesterol or a normal diet. The researchers also gave olive leaf extract to some of the rats in both groups.
After 8 weeks, the cholesterol-fed rats had higher levels of total cholesterol and low-density lipoprotein (LDL), or “bad,” cholesterol. In the rats that also consumed the olive leaf extract, these cholesterol levels were significantly lower.
These findings may also apply to humans. A 2008 study compared the effects of food supplementation with olive leaf extract with lifestyle advice in 40 identical twins with high blood pressure.
After 8 weeks, the team found that olive leaf extract significantly lowered LDL cholesterol levels within the twin pairs in a dose-dependent manner. This means that larger doses had a greater effect.
Olive leaf extract may help treat hypertension, or high blood pressure. In a 2011 study, researchers randomized people with stage 1 hypertension to take either 500 milligrams (mg) of olive leaf extract or 12.5–25 mg of captopril, a medication for high blood pressure, twice per day.
After 8 weeks, blood pressure was significantly lower for both groups. The team concluded that the olive leaf extract was as effective at lowering blood pressure in people with stage 1 hypertension as captopril.
In another study from 2017, researchers randomized people with stage 1 hypertension to take either an olive leaf extract containing 136 mg of oleuropein or a placebo each day.
After 6 weeks, the people who took the olive leaf extract had much lower blood pressure than those who took the placebo.
Olive leaf extract may also help reduce a person’s risk of developing type 2 diabetes.
In a 2013 study, researchers randomized 46 middle-aged men who were overweight to take either olive leaf extract or a placebo.
After 12 weeks, people in the olive leaf extract group had significant improvements in insulin sensitivity and pancreatic responsiveness compared with those who took a placebo.
Doctors consider reduced insulin sensitivity and pancreatic responsiveness to be important factors in the development of type 2 diabetes.