Olives and olive oil are staples of a healthy Mediterranean diet. Not only are they very high in antioxidants and healthy fats, but they are also full of dietary fiber and are great heart-healthy snacks.
Turns out that the fruit itself is not the only nutritional superstar – the leaves from the olive tree itself also pack a punch. A recent study published in the “American Journal of Plant Sciences” on Nov. 6 found that the extract could possibly help treat Type 2 diabetes by helping balance out blood sugar.
The study, led by professor Abdurrahim Koçyiğit, discovered that the leaves had antimicrobial, antihypertensive and anti-inflammatory properties, and their antihyperglycemic benefits were stronger when in extract form rather than brewed as a tea.

With a team of seven, Koçyiğit collected mature olives leaves in the western province of Tekirdağ and conducted a cell culture study on them for a year. The researchers tried different kinds of extraction methods in the study, from boiling and cold-pressing the leaves to soaking them in an alcohol solution. They came to the conclusion that using methanol was the most effective, delivering the most concentrated and standardized form of oleuropein (a polyphenol and compound that gives olives that bitter, spicy flavor) and was highly stable.
Koçyiğit explained that they worked with doctors actively monitoring which medicines and supplements patients were choosing to take for their health issues, and found that diabetes patients had a preference toward olive leaves, and consumed them in a variety of ways. Despite the number of patients that felt the leaves did not help with their diabetes being relatively low, they still saw other health benefits, he added.
Approximately 95% of all diabetes cases consist of Type 2, and insulin resistance is the main issue of the disease, Koçyiğit said. “Why does insulin resistance develop? There is already insulin (in the system). Our patients’ insulin levels are even higher than normal most of the time, but despite this, they still have high blood sugar. The reason behind this is the insulin receptors,” he said.
Underscoring that insulin needs these receptors to get glucose into the cell, Koçyiğit said these receptors drastically decreased in people who live sedentary lives or are overweight. A lack of receptors prevents glucose from entering the cell, and thus, it cannot be metabolized, he added.
This is where the extract comes into play, Koçyiğit said, as the polyphenols from olive leaves can increase insulin sensitivity and activity, as well as improve pancreatic responsiveness, helping the body better metabolize sugar.
However, the study pointed out that for maximum effect, it is essential to get the correct dosage, which will be determined after trials on animals and humans.
The researchers also cautioned that consuming too much of the extract could potentially bring more harm than good.