Scientists from the University of Tsukuba report that drinking tea made from olive leaves three times per day for 12 weeks led to significant decreases in triglycerides and cholesterol.
On the other hand, no changes were observed for body weight, waist circumference, and insulin levels between the olive leaf tea group and a control beverage, according to findings published in Nutrition Research.
“The present study is the first to report the serum lipid-lowering effect of OLT [olive leaf tea] in both men and women,” wrote the researchers. “Although such an effect may be limited to certain participants, our previous study has already shown that regular OLT intake leads to a significant decrease in WC [waist circumference] and FPG [fasting plasma glucose].”
The researchers recruited 57 people aged between 40 and 70 to participate in their parallel-group randomized control trial. The participants all had BMI levels between 23 and 29 kg/m2, and were classed as pre-diabetic. They consumed either the olive leaf tea (OLT) or a low-concentration OLT (LOLT) for 12 weeks. The OLT was made bt steeping five grams of olive leaves in one liter of boiled water, while the LOLT was prepared by steeping 0.5 grams in the same volume of water.
The results showed that LDL and triglyceride reductions were most pronounced in the OLT group.
In addition, the OLT group experienced significant reductions in fasting plasma glucose levels, compared to the LOLT group.
While no significant changes were observed for body weight, waist circumference, and insulin levels overall, when the scientists limited their analysis to participants with abdominal obesity, a significant effect of the OLT was observed.
The researchers pointed to oleuropein as the potential bioactive of interest in olive leaves, as it is the most abundant phenolic compound in the leaves. Data from other research groups and studies have linked olive polyphenols or oleuropein in particular to benefits in people with obesity, metabolic syndrome, or type 2 diabetes.
Commenting on the potential mechanism of action, the researchers noted that data from animal studies have suggested that oleuropein may reduce the activity of hydroxymethylglutaryl-CoA reductase, “the rate-limiting enzyme of cholesterol synthesis”.
“Further investigation is needed to confirm the effect of OLT for human health,” they concluded.
Source: Nutrition Research
Published online ahead of print, doi: 10.1016/j.nutres.2019.05.003
“Olive leaf tea is beneficial for lipid metabolism in adults with pre-diabetes: An exploratory randomized controlled trial”
Authors: R. Araki et al.