Zero effect of multiple dosage of olive leaf supplements on urinary biomarkers of oxidative stress in healthy humans

Objective: We determined the effect of dietary supplementation with an olive leaf capsule or liquid extract on oxidative status of young and healthy male and female subjects.Methods: This was a single-center, randomized, single-blinded, prospective pilot comparison of the effect of dietary supplementation with olive leaf extracts. Healthy young adult male and female subjects (n _ 45) were randomized into three groups and received daily doses of control, capsule, or liquid extract of olive leaf. Urinary F2'-isoprostane, 8-hydroxy-2'-deoxyguanosine, and Folin-Ciocalteu total reducing power were measured to assess the impact of supplementation.Results: Baseline values (mean _ standard deviation) of the biomarkers were 0.24 _ 0.13 _g, 9.16 _ 2.94 _g, and 424.9 _ 121.4 mg of gallic acid equivalents per gram of creatinine, respectively, for the control group. Using these markers, supplementation with liquid or capsule did not alter oxidative status compared with the control group. Possible reasons for the lack of an observed correlation are presented.Conclusion: Dietary supplementation with olive leaf extract did not alter the oxidative status of healthy young adults.