Absorption of Hydroxytyrosol from Different Sources and its Impact on Lipid Status in Human Subjects

Abstract

Background: There is growing interest in the health effects of dietary polyphenols on cardiovascular risk factors. In this context, the effect of hydroxytyrosol on lipid status was investigated in healthy subjects. Hydroxytyrosol, a polyphenol especially known from olive oil, is available on the market from different sources. Absorption from those sources is prerequisite for its effects. Methods: Here we report a study on the absorption and the effects of a pure, synthetic form of hydroxytyrosol compared to an olive extract and a placebo. The phenols hydroxytyrosol and homovanillic acid were chosen as markers in urine. The study was conducted as a mono-center, randomized, double-blind, placebo-controlled, three-way cross-over design with 30 healthy subjects. The four-week oral supplementation phases were separated by two-week wash-out phases. Results: Neither total cholesterol levels nor HDL (high-density lipoprotein)-cholesterol levels were significantly affected by the study preparations. However, a significant LDL (low-density lipoprotein)-cholesterol reduction was seen after intervention with the pure, synthetic hydroxytyrosol in comparison to placebo (p = 0.0003). LDL cholesterol levels were significantly reduced between the beginning and end of intervention with the pure hydroxytyrosol (delta LDL cholesterol -9.4 mg/dL ± 10.9 mg/dL, p = 0.0004), whereas no LDL-lowering effects were seen after the intervention with the olive extract or placebo (olive extract: delta LDL cholesterol: +2.1 mg/dL ± 15.2 mg/dL; placebo: delta LDL cholesterol: +4.1 mg/dL ± 15.4 mg/dL). The excreted amounts of hydroxytyrosol and homovanillic acid confirm the uptake of the study products in comparison to placebo (p < 0.0001). Overall the tolerability of the study products was very good. Conclusion: Our study supports the beneficial effects of pure hydroxytyrosol from a synthetic source on LDL cholesterol.