Mediterranean Diets Supplemented With Virgin Olive Oil and Nuts Enhance Plasmatic Antioxidant Capabilities and Decrease Xanthine Oxidase Activity in People With Metabolic Syndrome: The PREDIMED Study

Mol Nutr Food Res. 2016 Dec;60(12):2654-2664. doi: 10.1002/mnfr.201600450. Epub 2016 Oct 27.


Scope: This study assessed plasmatic antioxidant capabilities and xanthine oxidase (XOX) activity in metabolic syndrome patients after 5 years intervention with Mediterranean diet (MeDiet) supplemented with extra-virgin olive oil or with nuts or with low-fat diet (the PREDIMED [PREvención con Dieta MEDiterránea] study).

Methods and results: Seventy-five participants were randomly selected. Daily energy and nutrient intake were assessed with a validated 137-item food frequency questionnaire, and adherence to the MeDiet was assessed using a 14-item questionnaire. Catalase, superoxide dismutase (SOD), myeloperoxidase, XOX activities and protein levels, and protein carbonyl derivatives, nitrotyrosine, nitrite and nitrate levels were determined in overnight fasting venous blood samples. The plasma activity and protein levels of SOD and catalase were significantly higher and XOX activity was lower in MeDiet supplemented with extra-virgin olive oil and MeDiet supplemented with nuts than in the control group. Participants in both MeDiet groups showed higher plasma nitrate levels than in the control group. Adherence to the MeDiet showed a positive correlation with SOD and catalase plasma antioxidant activities.

Conclusion: A MeDiet enriched with either virgin olive oil or nuts enhances the plasma antioxidant capabilities and decreases XOX activity in patients with the metabolic syndrome but we did not observe changes in myeloperoxidase or markers of oxidative damage.

Keywords: Antioxidant enzymes; Nitrosative damage; Oxidative damage; PREDIMED; Pro-oxidant markers.

Publication types

  • Multicenter Study
  • Randomized Controlled Trial
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Aged
  • Aged, 80 and over
  • Biomarkers / blood
  • Catalase / blood
  • Cholesterol / blood
  • Diet, Fat-Restricted
  • Diet, Mediterranean*
  • Female
  • Follow-Up Studies
  • Humans
  • Male
  • Metabolic Syndrome / blood*
  • Metabolic Syndrome / diet therapy*
  • Middle Aged
  • Nutrition Assessment
  • Nuts*
  • Olive Oil / administration & dosage*
  • Patient Compliance
  • Peroxidase / blood
  • Superoxide Dismutase / blood
  • Surveys and Questionnaires
  • Tyrosine / analogs & derivatives
  • Tyrosine / blood
  • Xanthine Oxidase / antagonists & inhibitors
  • Xanthine Oxidase / blood*


  • Biomarkers
  • Olive Oil
  • 3-nitrotyrosine
  • Tyrosine
  • Cholesterol
  • Catalase
  • Peroxidase
  • Superoxide Dismutase
  • Xanthine Oxidase