Plain English Summary
Background and study aims
Virgin olive oil is widely used in Mediterranean food and has been associated with health benefits such as protection against heart disease. For many years, the beneficial properties of olive oil were attributed to a type of fat named oleic acid. Besides containing high quantities of oleic acid, some olive oils contain small molecules called phenolic compounds, which are known as natural antioxidants. Little is known about the fate of these compounds in the body once they are consumed, or where they do to influence health. This study aims to find out the contribution of phenolic compounds present in virgin olive oil to the prevention of diseases and promotion of health using new biomarker techniques (a biomarker is a small molecule acting as a reporter for health and disease).
Who can participate?
Healthy adults, aged 18-75, who are not allergic to olive products.
What does the study involve?
Your body weight, height, waist circumference and blood pressure will be recorded and you will fill in a questionnaire to help us establish your intake of foods rich in phenolic compounds. During the 6-week study period, you will be randomly allocated to take a daily dose of olive oil (20 ml) with either a high or low polyphenolic content, to be consumed uncooked. At the beginning, middle and end of the study, participants will be asked to keep a record of the food eaten the day before the visit, to collect a spot urine sample in a small tube (second urine of the day) and to provide a blood sample. We will measure, in urine and blood, the levels of small molecules (biomarkers) that are related to heart and kidney health, as well as the way food is digested, transformed in the body and excreted.
What are the possible benefits and risks of participating?
There are no benefits or risks associated with taking part in the trial.
Where is the study run from?
Not provided at time of registration.
When is the study starting and how long is it expected to run for?
The study started in July 2012 and ran for 6 weeks.
Who is funding the study?
University of Lisbon (Portugal).
Who is the main contact?
Dr William Mullen
Bioavailability of virgin olive oil bioactive compounds and impact of a 6-week supplementation on biomarkers of coronary artery disease, chronic kidney disease or diabetes
Can a 6-week supplemetation of olive oil with either a high or low polyphenolic content alter proteomic biomarkers of coronary artery disease, chronic kidney disease or diabetes?
Ethics committee of the University of Glasgow, College of Medical, Veterinary and Life Sciences, 31/08/2012, ref. 2012071.
Double-blind parallel supplementation study with low and high polyphenolic olive oil
Primary study design
Secondary study design
Randomised controlled trial
Patient information sheet
Patient information is available as a leaflet that can be obtained by contacting Dr Emilie Combet by telephone on 0141 201 0768 or via e-mail at firstname.lastname@example.org, or Dr Bill Mullen on 0141 330 6210 (email@example.com). A third party who will be able to advise on the general research process is Professor Mike Lean (firstname.lastname@example.org).
Risk of coronary artery disease, chronic kidney disease and diabetes
66 healthy volunteers will be randomly allocated into one of two groups and asked to consume 20 ml of olive oil per day for 6 weeks.
Group 1 will be given olive oil with a high polyphenolic content.
Group 2 will be given olive oil with a low polyphenolic content.
Blood and urine samples will be collected the day before the study starts and also after 3 weeks and at the end of the study. Blood pressure and weight will be recorded at these visits too.
Primary outcome measures
Proteomic urinary biomarkers of coronary artery disease, chronic kidney disease and diabetes. These will be measured after 3 weeks, the mid point and after 6 weeks, the end of the study.
Secondary outcome measures
Plasma-based biomarkers of heart disease and blood pressure. These will be measured after 3 weeks, the mid point and after 6 weeks, the end of the study.
Overall trial start date
Overall trial end date
Participant inclusion criteria
Healthy adults, aged 18-75 years
Target number of participants
Participant exclusion criteria
1. Those allergic to olive products
2. Currently taking medication (other than the contraceptive pill)
3. Have taken antibiotics in the last 3 months
4. Have received or are receiving treatments for any chronic gut disease
5. Is pregnant, trying to conceive, or lactating
Recruitment start date
Recruitment end date
Countries of recruitment
Trial participating centre
Institute of Cardiovascular and Medical Sciences
University of Lisbon, in collaboration with the Sovena company (Portugal)
Funding Body Type
Funding Body Subtype
Results and Publications
Publication and dissemination plan
Not provided at time of registration
Intention to publish date
Participant level data
Not provided at time of registration
Results - basic reporting
2015 results in: http://www.ncbi.nlm.nih.gov/pubmed/25527749
Silva S, Bronze MR, Figueira ME, Siwy J, Mischak H, Combet E, Mullen W, Impact of a 6-wk olive oil supplementation in healthy adults on urinary proteomic biomarkers of coronary artery disease, chronic kidney disease, and diabetes (types 1 and 2): a randomized, parallel, controlled, double-blind study, Am J Clin Nutr, 2015, 101, 1, 44-54, doi: 10.3945/ajcn.114.094219.