Olive leaf tea is beneficial for lipid metabolism in adults with prediabetes: an exploratory randomized controlled trial

Olive leaves are rich in oleuropein, which has been shown to have beneficial effects on dyslipidemia, type 2 diabetes, and obesity. However, we previously found no significant health benefits of olive leaf tea (OLT) on nonobese and nondiabetic individuals. Thus, we performed this study to further explore the health benefits of OLT in individuals with prediabetes and compare the health benefits between low-concentration OLT (LOLT) and OLT. We hypothesized that OLT will have a more pronounced effect on abdominal obesity as well as glucose and lipid metabolism in prediabetic individuals. Individuals between 40 and 70 years of age with a body mass index of 23.0-29.9 kg/m(2) and prediabetes status were recruited and randomly assigned to the OLT or the LOLT group. The intervention, which was the consumption of 330 mL of the test beverage 3 times daily during mealtime, lasted for 12 weeks. After the intervention, serum levels of log-transformed triglycerides (P < .05) and low-density lipoprotein cholesterol (P < .01) decreased significantly in the OLT group (n = 28), with the reductions higher in the OLT group than those in the LOLT group (n = 29, log-transformed triglycerides: P = .079, low-density lipoprotein cholesterol: P < .05). Whereas body weight, waist circumference, and insulin levels were not significantly changed in both groups, fasting plasma glucose levels in the OLT group were significantly decreased compared to those in the LOLT group (P < .05). In conclusion, although the effect of OLT on abdominal obesity and glucose metabolism remains unclear, OLT has been found to have lipid-lowering effects. (C) 2019 Elsevier Inc. All rights reserved.