Entry #: 33
Date: 26 January 2018
Section: Phenol-enriched olive oil
Topic: Phenol-enriched olive oil and hypercholesterolemia
Type: Human volunteer trial

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D. Elizabeth McCord, Nancy B. Ray and Tom C. Karagiannis


Phenol-enriched olive oils improve HDL antioxidant content in hypercholesterolemic subjects. A randomized, double-blind, cross-over, controlled trial


Farrás et al

Citation / Year

(1) / 2018


Phenol-enriched olive oil, thyme phenolics, phenolic compounds, high-density lipoprotein, hypercholesterolemia, α-tocopherol


This study represents an important extension of previous work conducted by this group in the context of high density lipoprotein function (HDL) and modulation with virgin olive oil. As explained by the authors, HDL is responsible for carrying excess cholesterol from peripheral cells (cholesterol efflux) for metabolism in the liver and excretion (1). Findings from the EUROLIVE study, have indicated the association of the phenolic content of olive oils with improved HDL concentrations and decreased oxidative stress and oxidative damage in healthy volunteers (2-4). Further, the authors this study have shown the beneficial effects of virgin olive oil at the cellular level highlighting improved cholesterol efflux, monolayer fluidity, and HDL phenolic content (5). In this study the overall aim was to extend these earlier findings by investigating the role of complementary phenolic compounds. This was achieved by enriching the phenolic content of virgin olive oil with those from thyme (Thymis zygis) extracts, an approach that is gaining considerable research interest (6, 7).

Key points and implications

A total of 33 (19M, 14 F) hypercholesterolemic (57.6% on medication) volunteers participated in this study. Following a two-week washout period with common olive oil, people were randomized into three groups with different sequences of administration of raw olive oils (for three weeks) in a cross-over study design. A low phenolic content olive oil (80 ppm) was used a control and provided the basis for the two enriched olive oils. One of the olive oils was enriched with its own phenolic compounds from a freeze-dried extract (at 500 ppm), and the other with 50% olive phenolics and 50% phenolics from extract of commercial dried thyme (at 500 ppm). In summary the three groups were: 1) low content phenolic olive oil, 2) olive oil enriched with olive phenolics, and 3) olive oil enriched with olive and thyme phenolics. People ingested 25 mL/day of the appropriate raw olive oil for a three week period. In summary, the findings indicated 1) an increase in HDL antioxidant content with both the olive phenolic-enriched olive oil and thyme phenolic-enriched olive oils compared to control, and 2) the thyme phenolic-enriched olive oil increased levels of the major HDL antioxidant, α-tocopherol. These findings highlight the importance of the potential health benefits of complementary phenolics, which represents and interesting, emerging, and exciting field of research.

Related publications

  1. M. Farras et al., Phenol-enriched olive oils improve HDL antioxidant content in hypercholesterolemic subjects. A randomized, double-blind, cross-over, controlled trial. The Journal of nutritional biochemistry 51, 99-104 (2018).
  2. O. Castaner et al., The effect of olive oil polyphenols on antibodies against oxidized LDL. A randomized clinical trial. Clinical nutrition 30, 490-493 (2011).
  3. M. I. Covas et al., The effect of polyphenols in olive oil on heart disease risk factors: a randomized trial. Annals of internal medicine 145, 333-341 (2006).
  4. A. Machowetz et al., Effect of olive oils on biomarkers of oxidative DNA stress in Northern and Southern Europeans. FASEB journal : official publication of the Federation of American Societies for Experimental Biology 21, 45-52 (2007).
  5. A. Hernaez et al., Olive oil polyphenols enhance high-density lipoprotein function in humans: a randomized controlled trial. Arteriosclerosis, thrombosis, and vascular biology 34, 2115-2119 (2014).
  6. M. Romeu et al., Virgin Olive Oil Enriched with Its Own Phenols or Complemented with Thyme Phenols Improves DNA Protection against Oxidation and Antioxidant Enzyme Activity in Hyperlipidemic Subjects. Journal of agricultural and food chemistry 64, 1879-1888 (2016).
  7. S. Martin-Pelaez et al., Effect of virgin olive oil and thyme phenolic compounds on blood lipid profile: implications of human gut microbiota. European journal of nutrition 56, 119-131 (2017).