Olive Oil Polyphenols and Cardiovascular Health Biomarkers

The purpose of this research is to investigate whether consuming two different kinds of olive oil will change risk factors related to cardiovascular disease, including levels of good and bad cholesterol, levels of inflammation, and levels of gene expression.

Study Overview

• Status: Active, not recruiting
• Conditions: Healthy; Overweight; Obese; Normal Weight
• Intervention / Treatment: Dietary supplement: High-polyphenol olive oil; Dietary supplement: Low-polyphenol olive oil

Detailed Description

The purpose of this research is to investigate whether consuming two different kinds of olive oil will change risk factors related to cardiovascular disease, including levels of good and bad cholesterol, levels of inflammation, and levels of gene expression. Healthy individuals aged 20-45 with a BMI over 20 kg/m2 are eligible to participate. The study involves 5 visits (1 initial screening and 4 study visits) and will last about 8 weeks. There is a 2-week run-in period before starting the study, followed by two diet intervention periods each lasting two weeks, separated by a two-week washout period.

Participation in this study will involve an initial two-week run in period to become accustomed to the study diet. After this two week period, participants will be randomly selected to start either a high-polyphenol olive oil (extra virgin olive oil) or a low-polyphenol olive oil (refined olive oil); participants will consume the other oil during the second dietary intervention period lasting 2 weeks. During each phase of the study, participants will be asked to come to the University of California, Davis campus after a 10-12 hour overnight fast. At each visit, body measurements will be taken, a serving of olive oil and bread will be eaten, and three urine and blood samples will be collected over the course of 4 hours. Each study visit will involve three blood draws by a trained nurse or phlebotomist.

During the 8 weeks of the study, all olive products such as olives, olive oil, and olive containing products will need to be avoided. The study will provide olive oil to be eaten at home for each intervention phase. Additionally, the investigators will ask that nuts and high-polyphenol foods (mostly fruits and vegetables) be avoided in the diet. Detailed food diaries will be filled out and brought to study visits.

• Study Type: Interventional
• Enrollment (Estimated): 44
• Phase: Not Applicable

Contacts and Locations

Study Locations

• United States
  • California
    • Davis, California, United States, 95616
      • Ragle Human Nutrition Center

Participation Criteria

Eligibility Criteria

• Ages Eligible for Study: 16 years to 41 years (Adult)
• Accepts Healthy Volunteers: Yes

Description

Inclusion Criteria:

• Generally healthy male and female subjects within the range of 20-45 years of age and BMI range of 18.5-29.9 kg/m2 for the healthy weight/overweight group and ≥ 30 kg/m2 for the obese group will be recruited.

Exclusion Criteria:

• Adults unable to consent, individuals who are not yet adults (infants, children, teenagers), pregnant or lactating women, women planning to become pregnant in the next two months and prisoners will be specifically excluded
• Documented chronic diseases including diabetes, thyroid disease, kidney disease, metabolic syndrome, active cancer, previous cardiovascular events, history of gastric bypass or other GI issues related to fat absorption
• History of dyslipidemia or abnormal blood glucose levels (total cholesterol >240 mg/dL, elevated fasting blood glucose levels >125 mg/dL)
• Allergy to olives, inability to tolerate gluten or multiple allergies/intolerances that would significantly limit food intake
• Smoker or living with a smoker, illicit drug use, consuming >1 alcoholic drink/day, vaporizer and/or electronic cigarette use
• Extreme dietary or exercise patterns
• Recent weight fluctuations (>10% in the last 6 months)
• Taking prescription lipid medications or supplements that may affect lipoprotein metabolism, >1 g of fish oil/day, antioxidant supplements, cannabidiol (CBD) oil
• Taking exogenous hormones (e.g. hormonal birth control)
• Poor venous access
• Unwillingness to comply with study protocol

Study Plan

How is the study designed?

Design Details

• Primary Purpose: Basic Science
• Allocation: Randomized
• Interventional Model: Crossover Assignment
• Masking: Single

Number of Arms

2

Arms and Interventions

Participant Group / Arm	Intervention / Treatment
Active Comparator: High-polyphenol olive oil; Participants will consume 40 mL of high-polyphenol olive oil each day at home for 2 weeks.	Dietary supplement: High-polyphenol olive oil; High-polyphenol olive oil will be provided to study participants to consume at home. Participants will be asked to consume 40 mL each day for 2 weeks.
Active Comparator: Low-polyphenol olive oil; Participants will consume 40 mL of low-polyphenol olive oil each day at home for 2 weeks.	Dietary supplement: Low-polyphenol olive oil; Low-polyphenol olive oil will be provided to study participants to consume at home. Participants will be asked to consume 40 mL each day for 2 weeks.

What is the study measuring?

Primary Outcome Measures

Outcome Measure	Measure Description	Time Frame
Assessing the influence of olive oil polyphenols on cholesterol efflux	Cholesterol efflux will be measured by assessing changes in reverse cholesterol transport rate in separated serum at each study time point (baseline, 2 hour, 4 hour) using a commercially available assay kit at each of the 4 study visits.	Through study completion, an average of 8 weeks
Assessing the influence of olive oil polyphenols on cholesterol ester transfer protein activity (CETP)	Changes in CETP activity will be measured at each study time point (baseline, 2 hour, 4 hour) in plasma at each of the 4 study visits. The isolated plasma will be co-incubated with donor and acceptor molecules using a commercially available assay kit.	Through study completion, an average of 8 weeks
Assessing the influence of olive oil polyphenols on circulating oxidized LDL	Measure for changes in circulating levels of oxidized LDL in separated plasma at each study time point (baseline, 2 hour, 4 hour) using a commercially available ELISA kit; measured in units of U/L at each of the 4 study visits.	Through study completion, an average of 8 weeks
Assessing the influence of olive oil polyphenols on blood lipid measurements	Measure for changes in the levels of HDL and LDL in separated plasma; measured in units of mg/dL. Blood will be assessed for the fasting (baseline) sample only at each of the 4 study visits.	Through study completion, an average of 8 weeks
Assessing the influence of olive oil polyphenols on paraoxonase-1 (PON-1) activity	Measure for changes in PON-1 activity in separated plasma at each study time point (baseline, 2 hour, 4 hour) at each of the 4 study visits. Activity will be calculated based on linear rates of hydrolysis of phenyl acetate to phenol.	Through study completion, an average of 8 weeks
Assessing the influence of olive oil polyphenols on peripheral blood mononuclear cells (PBMC) using ex vivo stimulation assays	Measurement of changes in PBMC derived cytokines as a marker of inflammation at each study time point (baseline, 2 hour, 4 hour) at each of the 4 study visits. Assessment will be based on an increase or decrease in concentration in pg/ml.	Through study completion, an average of 8 weeks

Secondary Outcome Measures

Outcome Measure	Measure Description	Time Frame
Assessing the influence of olive oil polyphenols on gene expression in mirco RNA in PBMCs	Measure level of gene expression in micro RNA from PBMCs at each study time point (baseline, 2 hour, 4 ) at each of the 4 study visits. Assessment will be based on fold change between study arms.	Through study completion, an average of 8 weeks

Other Outcome Measures

Outcome Measure	Measure Description	Time Frame
Food record analysis	Use a computer program to check for study dietary requirements. Subjects are to avoid olives and olive containing products during study protocol periods. This will be done using a subject self-recorded 3-day food record submitted to study personnel.	Through study completion, an average of 8 weeks
Anthropometric measurements	Measure waist (cm) and hip circumference (cm) before the start of drawing blood on study day protocols.	Through study completion, an average of 8 weeks
Measure for changes in weight	Measure weight (kg) before the start of drawing blood on study day protocols.	Through study completion, an average of 8 weeks
Measure for changes in blood pressure	Measure blood pressure (mmHg) before the start of drawing blood on study day protocols.	Through study completion, an average of 8 weeks
Assessing the influence of olive oil polyphenols on circulating cytokines	Measure circulating cytokines in separated plasma at each study time point (baseline, 2 hour, 4 hour) at each of the 4 study visits. Commercially available ELISA kits will be used: TNF-a, IL-6, IL-1B, MCP-1, and ET-1.	Through study completion, an average of 8 weeks
Assessing the influence of olive oil polyphenols on urine metabolites	Metabolomics will be performed on urine to assess for study compliance of consumption of the polyphenol containing olive oil versus the low-polyphenol containing olive oil at each of the 4 study visits.	Through study completion, an average of 8 weeks

Collaborators and Investigators

• Sponsor: University of California, Davis

Publications and helpful links

Helpful Links

• Learn more or sign up for the study here!

Study record dates

Study Major Dates

• Study Start (Actual): October 6, 2021
• Primary Completion (Estimated): August 22, 2026
• Study Completion (Estimated): August 22, 2026

Study Registration Dates

• First Submitted: September 30, 2019
• First Submitted That Met QC Criteria: October 31, 2019
• First Posted (Actual): November 4, 2019

Study Record Updates

• Last Update Posted (Actual): January 29, 2026
• Last Update Submitted That Met QC Criteria: January 27, 2026
• Last Verified: January 1, 2026

More Information

Terms related to this study

• Additional Relevant MeSH Terms: Nutrition Disorders; Overnutrition; Body Weight; Pathological Conditions, Signs and Symptoms; Nutritional and Metabolic Diseases; Signs and Symptoms; Overweight; Obesity
• Other Study ID Numbers: 1484263

Drug and device information, study documents

• Studies a U.S. FDA-regulated drug product: No
• Studies a U.S. FDA-regulated device product: No