In addition to the effects of the mono-unsaturated fatty acid oleic acid, olive oil and olive extracts contain polyphenols with remarkable health benefits. Of these, extracts concentrated for oleuropein have been shown to lower blood pressure (BP) and cholesterol levels. Often olive extracts are concentrated for hydroxytyrusol, a metabolite of oleuropein that exerts some antioxidant effects, but this compound is devoid of any significant effect on BP or cholesterol levels.
Studies utilizing an olive leaf extract standardized to oleuropein (16-24%) and polyphenols have shown considerable benefits to heart health. For example, in the largest trial, 232 patients with high BP were given either this olive leaf extract (500 mg twice daily) or the conventional antihypertensive drug Captopril (12.5 mg twice daily). Average BP at baseline was 149.3/93.9 mmHg in the olive group and 148.4/93.8 mmHg in Captopril group. Averages of systolic BP reduction from baseline to the end of study were -11.5 and -13.7 mmHg in olive and Captopril groups, respectively; and those of diastolic BP were -4.8 and -6.4 mmHg, respectively. In other words, olive extract lowered BP as well as the drug.
In addition to lowering BP, both oleic acid and olive polyphenols have been shown to lower LDL cholesterol while increasing HDL cholesterol as well as protect either form from oxidation. A new study shows that olive polyphenols produce these effect via a very complex action on the expression of genes. The primary changes in gene expression were due to a decrease in oxidized LDL as a result of an increase in the antioxidant capacity of the blood.
What makes this research new is the explanation of the observed effect. Researchers already knew that olive polyphenols exerted antioxidant effects what this study showed is that as the result of this effect gene expression was significantly affected in a way that provides an additional mechanism explaining the beneficial effects of olive polyphenols.
Farràs M, Valls RM, Fernández-Castillejo S, et al. Olive oil polyphenols enhance the expression of cholesterol efflux related genes in vivo in humans. A randomized controlled trial. J Nutr Biochem. 2013 Jan 17 [Epub ahead of print]