Olea europaea leaf extract has demonstrated antidiabetic properties by improving insulin sensitivity and reducing fasting blood glucose levels. Its primary active compound, oleuropein, has been shown to modulate glucose metabolism, enhance insulin secretion, and inhibit enzymes involved in carbohydrate digestion. Olive leaf extract also possesses potent antioxidant and anti-inflammatory effects, which help protect pancreatic β-cells and mitigate oxidative stress—key factors in the progression of type 2 diabetes.

References:

De Bock M, Derraik JG, Brennan CM, Biggs JB, Morgan PE, Hodgkinson SC, Hofman PL, Cutfield WS. Olive (Olea europaea L.) leaf polyphenols improve insulin sensitivity in middle-aged overweight men: a randomized, placebo-controlled, crossover trial. PLoS One. 2013;8(3):e57622. 
Wainstein J, Ganz T, Boaz M, Bar Dayan Y, Dolev E, Kerem Z, Madar Z. Olive leaf extract as a hypoglycemic agent in both human diabetic subjects and in rats. J Med Food. 2012 Jul;15(7):605-10.
Leach MJ, Breakspear I. Efficacy and safety of olive leaf extract (Olea europaea L.) for glycaemic control in adults with type 2 diabetes mellitus (ESOLED): A pilot randomised controlled trial. Complement Ther Clin Pract. 2025 May;59:101949.
Zheng, S., Huang, K., & Tong, T. (2021). Efficacy and mechanisms of oleuropein in mitigating diabetes and diabetes complications. Journal of Agricultural and Food Chemistry, 69(22), 6145-6155.‏
Annunziata, G., Maisto, M., Schisano, C., Barrea, L., Ciampaglia, R., Narciso, V., ... & Novellino, E. (2018). Oleuropein as a novel anti-diabetic nutraceutical. An overview. Archives of Diabetes & Obesity, 1(3), 54-58.‏
Álvares, A. A., Garcêz, A., Silva, L. T., Averbuch, N., & Garavaglia, J. (2024). Olive leaf extract effect on cardiometabolic risk factors: A systematic review and meta-analysis of randomized clinical trials. Nutrition Reviews, 82(12), 1710-1725.​​