The Effect of Polyphenols in Olive Oil on Heart Disease Risk Factors

A Randomized Trial

5 September 2006 | Volume 145 Issue 5 | Pages 333-341

Background: Virgin olive oils are richer in phenolic content than refined olive oil. Small, randomized, crossover, controlled trials on the antioxidant effect of phenolic compounds from real-life daily doses of olive oil in humans have yielded conflicting results. Little information is available on the effect of the phenolic compounds of olive oil on plasma lipid levels. No international study with a large sample size has been done.

Objective: To evaluate whether the phenolic content of olive oil further benefits plasma lipid levels and lipid oxidative damage compared with monounsaturated acid content.

Design: Randomized, crossover, controlled trial.

Setting: 6 research centers from 5 European countries.

Participants: 200 healthy male volunteers.

Measurements: Glucose levels, plasma lipid levels, oxidative damage to lipid levels, and endogenous and exogenous antioxidants at baseline and before and after each intervention.

Intervention: In a crossover study, participants were randomly assigned to 3 sequences of daily administration of 25 mL of 3 olive oils. Olive oils had low (2.7 mg/kg of olive oil), medium (164 mg/kg), or high (366 mg/kg) phenolic content but were otherwise similar. Intervention periods were 3 weeks preceded by 2-week washout periods.

Results: A linear increase in high-density lipoprotein (HDL) cholesterol levels was observed for low-, medium-, and high-polyphenol olive oil: mean change, 0.025 mmol/L (95% CI, 0.003 to 0.05 mmol/L), 0.032 mmol/L (CI, 0.005 to 0.05 mmol/L), and 0.045 mmol/L (CI, 0.02 to 0.06 mmol/L), respectively. Total cholesterol–HDL cholesterol ratio decreased linearly with the phenolic content of the olive oil. Triglyceride levels decreased by an average of 0.05 mmol/L for all olive oils. Oxidative stress markers decreased linearly with increasing phenolic content. Mean changes for oxidized low-density lipoprotein levels were 1.21 U/L (CI, –0.8 to 3.6 U/L), –1.48 U/L (–3.6 to 0.6 U/L), and –3.21 U/L (–5.1 to –0.8 U/L) for the low-, medium-, and high-polyphenol olive oil, respectively.

Limitations: The olive oil may have interacted with other dietary components, participants' dietary intake was self-reported, and the intervention periods were short.

Conclusions: Olive oil is more than a monounsaturated fat. Its phenolic content can also provide benefits for plasma lipid levels and oxidative damage.

International Standard Randomised Controlled Trial number: ISRCTN09220811.

Editors' Notes Context Olive oil, the main fat in the Mediterranean diet, contains polyphenols, which have antioxidant properties and may affect serum lipid levels. Contribution The authors studied virgin olive oil (high in polyphenols), refined olive oil (low in polyphenols), and a mixture of the 2 oils in equal parts. Two hundred healthy young men consumed 25 mL of an olive oil daily for 3 weeks followed by the other olive oils in a randomly assigned sequence. Olive oils with greater polyphenol content increased high-density lipoprotein (HDL) cholesterol levels and decreased serum markers of oxidation. Cautions The increase in HDL cholesterol level was small. Implications Virgin olive oil might have greater health benefits than refined olive oil. —The Editors

 

Author and Article Information

From the Municipal Institute for Medical Research, Barcelona, Spain; University of Kuopio and Oy Jurilab, Kuopio, Finland; Rigshospitalet, University Hospital, Copenhagen, Denmark; German Institute of Human Nutrition, Postdam-Rehbruecke, Germany; Charité-University of Medicine of Berlin, Berlin, Germany; and Centro per lo Studio dell'Arteriosclerosi e delle Malattie Dismetaboliche "GC Descovich," Policlinico S. Orsola-Malpighi, Bologna, Italy.

Acknowledgments: The authors thank the EUROLIVE Investigators: R. Elosua, J.S. Vila, H. Schroder, and M. Farré-Albaladejo, Municipal Institute for Medical Research (IMIM), Barcelona, Spain, for methodologic and statistical assistance, performing diet record analyses, and management assistance; S. Voutilainen, T. Rissanen, T.P. Tuomainen, and V.P. Valkonen, Research Institute of Public Health, Kuopio University, Kuopio, Finland, for management and technical assistance; S. D'Addato, E. Grandi, S. Linarello, Z. Sangiorgio, and A. Fiorito, Policlinico S. Orsola-Malpighi, Bologna, Italy, for technical assistance and performing diet record analyses; T. Vilppo, Oy Jurilab, Kuopio, Finland, for performing oxidative and antioxidative biomarkers; and M.C. López-Sabater, K. De la Torre, and R.M. Lamuela-Raventós, Barcelona University, Barcelona, Spain, for the olive oil analyses.

Grant Support: By grant QLK1-CT-2001-00287 from the Commission of the European Communities Quality of Life and Management of Living Resources program.

Potential Financial Conflicts of Interest: None disclosed.

Requests for Single Reprints: María-Isabel Covas, PhD, Lipids and Cardiovascular Epidemiology Unit, Municipal Institute for Medical Research (IMIM), Carrer Dr. Aiguader, 80, 08003 Barcelona, Spain; e-mail, mcovas{at}imim.es.

Current Author Addresses: Drs. Covas, Fitó, and Marrugat: Lipids and Cardiovascular Epidemiology Unit, Municipal Institute for Medical Research (IMIM), Carrer Dr. Aiguader, 80, 08003 Barcelona, Spain.

Dr. Nyyssönen, Mr. Mursu, and Mr. Virtanen: Research Institute of Public Health, University of Kuopio, Harjulantie 1B, 70211 Kuopio, Finland.

Dr. Poulsen: Department of Clinical Pharmacology, Rigshospitalet, University Hospital Copenhagen, 20 Tagensvej, 2200 Copenhagen, Denmark.

Drs. Kaikkonen and Salonen: Oy Jurilab, Neulaniementie 2L 12, 70210 Kuopio, Finland.

Dr. Zunft: German Institute of Human Nutrition (DIFE), Arthur-Scheunert-Allee, 114-116, 14558 Postdam-Rehbruecke, Germany.

Drs. Kiesewetter and Bäumler: Charité-University of Medicine of Berlin, Schumannstr, 20/21, 10117 Berlin, Germany.

Drs. Gaddi and Nascetti: Dipartimento di Medicina Clinica e Biotecnologia Applicata, Policlinico S. Orsola-Malpighi, Via Massarenti, 9, 40138 Bologna, Italy.

Dr. de la Torre: Pharmacology Research Unit, Municipal Institute for Medical Research (IMIM), Carrer Dr. Aiguader, 80, 08003 Barcelona, Spain.

Author Contributions: Conception and design: M.-I. Covas, K. Nyyssönen, H.E. Poulsen, H.-J.F. Zunft, H. Kiesewetter, A. Gaddi, J.T. Salonen, J. Marrugat.

Analysis and interpretation of the data: M.-I. Covas, J. Kaikkonen, H. Kiesewetter, R. de la Torre, J. Mursu, J. Marrugat.

Drafting of the article: M.-I. Covas, R. de la Torre, J. Marrugat.

Critical revision of the article for important intellectual content: K. Nyyssönen, H.E. Poulsen, J. Kaikkonen, H.-J.F. Zunft, H. Kiesewetter, A. Gaddi, J. Mursu, H. Bäumler, S. Nascetti, J.T. Salonen, M. Fitó, J. Virtanen, J. Marrugat.

Final approval of the article: M.-I. Covas, K. Nyyssönen, H.E. Poulsen, J. Kaikkonen, H.-J.F. Zunft, A. Gaddi, R. de la Torre, H. Bäumler, S. Nascetti, J.T. Salonen, M. Fitó, J. Marrugat.

Provision of study materials or patients: K. Nyyssönen, H.E. Poulsen, A. Gaddi, S. Nascetti, M. Fitó, J. Marrugat.

Obtaining of funding: M.-I. Covas, K. Nyyssönen, J. Kaikkonen, H.-J.F. Zunft, H. Kiesewetter, J.T. Salonen, J. Marrugat.

Administrative, technical, or logistic support: J. Mursu, H. Bäumler, J. Virtanen.

Collection and assembly of data: K. Nyyssönen, J. Kaikkonen, H.-J.F. Zunft, H. Bäumler, S. Nascetti, M. Fitó, J. Virtanen.

Read all Rapid Responses

questioning dosage

James B Roufs

Annals Online, 8 Sep 2006 [Full text]

Do interactions of olive oil-derived polyphenols and iron produce an antioxidant effect in vivo?

Luca Mascitelli, et al.

Annals Online, 27 Sep 2006 [Full text]

Can Polyphenols Protect Against Endotelial Dysfunction in Coronary Artery Disease?

Viola Vargova, et al.

Annals Online, 4 Oct 2006 [Full text]

Differential Effect of Olive Oil

Bruce L. Ring

Annals Online, 17 Oct 2006 [Full text]

Olive Oil--Effect on Other Disease Risk Factors

James A Craner

Annals Online, 7 Nov 2006 [Full text]

Polyphenols from olive oil an iron metabolism

Marķa Isabel Covas, et al.

Annals Online, 7 Nov 2006 [Full text]

Polyphenolic content in olive oil and bioactivity

Marķa Isabel Covas

Annals Online, 7 Nov 2006 [Full text]