Neuroprotective Effects of Oleanolic Acid and Erythrodiol in Prodromal Alzheimer's Disease (NEUROLEA)

September 22, 2026 updated by: Elena M. Yubero-Serrano, Spanish National Research Council

Alzheimer's disease begins many years before memory problems become obvious. People in the early ("prodromal") stage have memory complaints but are still independent in daily life. At present there is no treatment that prevents this stage from progressing to dementia.

Olive oil contains two natural compounds, oleanolic acid and erythrodiol. Earlier work by this research team suggests that these compounds may reduce inflammation and oxidative stress and may improve the way the body handles sugars and fats, processes that are also altered in Alzheimer's disease.

This study will test whether consuming olive oils that contain these compounds delays the progression from prodromal Alzheimer's disease to dementia.

A total of 120 adults aged 50 to 80 years with prodromal Alzheimer's disease will take part at three public hospitals in southern Spain. Participants will be assigned by chance to one of three groups and will consume 55 mL per day of one of three oils for 12 months: olive oil enriched with oleanolic acid, pomace olive oil (which naturally contains both compounds), or a standard commercial olive oil with very low levels of these compounds. Neither the participants nor the staff assessing them will know which oil each person is receiving.

Participants will attend study visits at the start of the study and after 6 and 12 months. At these visits they will complete memory and thinking tests, a physical and nutritional assessment, and blood and urine tests.

Study Overview

Status

Status

Indicates the current recruitment status or the expanded access status.
Not yet recruiting

Conditions

Conditions

The disease, disorder, syndrome, illness, or injury that is being studied. On ClinicalTrials.gov, conditions may also include other health-related issues, such as lifespan, quality of life, and health risks.

Intervention / Treatment

Intervention / Treatment

A process or action that is the focus of a clinical study. Interventions include drugs, medical devices, procedures, vaccines, and other products that are either investigational or already available. Interventions can also include noninvasive approaches, such as education or modifying diet and exercise.

Detailed Description

NEUROLEA is a multicenter, randomized, double-blind, controlled dietary intervention trial coordinated by the Instituto de la Grasa (CSIC). Participants will be recruited at the Neurology Units of Hospital Universitario Virgen del Rocío, Hospital Universitario Reina Sofía and Hospital Universitario de Valme.

Study oils. High-purity crystalline oleanolic acid (>95%) will be obtained from olive leaves following a procedure developed by the research team (Spanish Patent ES2160553) and used to prepare an oleanolic acid-enriched olive oil (600 mg/kg) according to European Patent EP18382510. A commercial olive oil 0.4° will serve as the control oil, as it has the same fatty acid composition as the other oils but a very low content of minor bioactive components. Pomace olive oil, which naturally contains oleanolic acid and erythrodiol, will be purchased from local markets. Oil composition will be verified by gas chromatography and differential scanning calorimetry before the intervention begins.

Randomization and blinding. Allocation will follow computer-generated random numbers prepared by the trial coordinator. Participants, clinical and nutritional research staff, and the neuropsychologists scoring the cognitive assessments will be blinded to group assignment.

Sample size. Thirty-four participants per arm are required for 90% power to detect a 10% reduction in dementia incidence in the functional oil arms compared with a 25% incidence in the control arm over 12 months (alpha 0.05). Allowing for up to 15% attrition in a long-term dietary intervention, the target is 40 participants per arm (120 in total).

Intervention and follow-up. Participants will consume 55 mL/day of the assigned oil, preferably raw and distributed across the three main meals, for 12 months. Adherence will be assessed with the self-reported Haynes-Sackett compliance test and by return of empty bottles, methods previously used by this team in the PREDIABOLE and OLTRAD trials. Participants and their caregivers will receive general healthy-eating guidance throughout the study.

Assessments. Evaluations will be performed at baseline and after 6 and 12 months, and will include a comprehensive neuropsychological battery, clinical examination, anthropometry and body composition by bioimpedance, dietary intake and diet quality questionnaires, and fasting blood and urine sampling. Serum concentrations of oleanolic acid and erythrodiol will be measured by HPLC-MS to verify exposure.

Mechanistic analyses. Beyond the clinical endpoints, the trial will examine circulating markers of lipid and glucose metabolism, oxidative stress and inflammation, and advanced glycation end product metabolism, together with the expression of related genes in peripheral blood mononuclear cells. Blood-based markers of Alzheimer's disease pathology (p-tau 217, neurofilament light chain, glial fibrillary acidic protein, and the amyloid beta 42/40 ratio) will be quantified at baseline and 12 months.

Data will be managed in REDCap and stored in pseudonymized form in accordance with the General Data Protection Regulation.

Study Type

Study Type

Describes the nature of a clinical study. Study types include interventional studies (also called clinical trials), observational studies (including patient registries), and expanded access.
Interventional

Enrollment (Estimated)

Enrollment

The number of participants in a clinical study. The "anticipated" enrollment is the target number of participants that the researchers need for the study.
120

Phase

Phase

The stage of a clinical trial studying a drug or biological product, based on definitions developed by the U.S. Food and Drug Administration (FDA). The phase is based on the study's objective, the number of participants, and other characteristics. There are five phases: Early Phase 1 (formerly listed as Phase 0), Phase 1, Phase 2, Phase 3, and Phase 4. Not Applicable is used to describe trials without FDA-defined phases, including trials of devices or behavioral interventions.
  • Not Applicable

Contacts and Locations

This section provides the contact details for those conducting the study, and information on where this study is being conducted.

Study Contact

Study Contact

The name and contact information for the person who can answer enrollment questions for a clinical study. Each location where the study is being conducted may also have a specific contact, who may be better able to answer those questions.

Study Locations

  • Spain
      • Seville, Spain, 41013
        • Instituto de la Grasa, CSIC
        • Contact:

Participation Criteria

Researchers look for people who fit a certain description, called eligibility criteria. Some examples of these criteria are a person's general health condition or prior treatments.

Eligibility Criteria

Eligibility Criteria

The key requirements that people who want to participate in a clinical study must meet or the characteristics they must have. Eligibility criteria consist of both inclusion criteria (which are required for a person to participate in the study) and exclusion criteria (which prevent a person from participating). Types of eligibility criteria include whether a study accepts healthy volunteers, has age or age group requirements, or is limited by sex.

Ages Eligible for Study

50 years to 80 years (Adult, Older Adult)

Accepts Healthy Volunteers

No

Genders Eligible for Study

All

Description

Inclusion Criteria:

Men and women aged 50 to 80 years Diagnosis of prodromal Alzheimer's disease, meeting all of the following: memory complaints corroborated by a reliable informant; Mini-Mental State Examination (MMSE) total score between 22 and 30; Free and Cued Selective Reminding Test (FCSRT, picture version) total recall score of 46 or less; Clinical Dementia Rating Global Score (CDR-GS) of 0.5; functional independence in activities of daily living (Functional Activities Questionnaire total score of 8 or less); plasma p-tau 217 above 0.45 pg/mL measured by the Lumipulse method Ability and willingness to attend scheduled visits at the study center Adequate visual and auditory capacity to complete study evaluations Educational level sufficient to read and write Written informed consent

Exclusion Criteria:

Absence of a reliable informant Evidence, based on medical history or clinical evaluation, of a neurological condition other than Alzheimer's disease that could account for the cognitive impairment Clinically significant, advanced or unstable systemic disease that may interfere with cognitive evaluation Severe psychiatric disorders, including schizophrenia, bipolar disorder or active major depression History of alcohol or psychotropic substance abuse Pre-existing intellectual disability that precludes neuropsychological evaluation

Study Plan

This section provides details of the study plan, including how the study is designed and what the study is measuring.

How is the study designed?

Design Details

  • Primary Purpose: Prevention
  • Allocation: Randomized
  • Interventional Model: Parallel Assignment
  • Masking: Quadruple

Arms and Interventions

Participant Group / Arm

Participant Group / Arm

A group or subgroup of participants in a clinical trial that receives a specific intervention/treatment, or no intervention, according to the trial's protocol.
Intervention / Treatment

Intervention / Treatment

A process or action that is the focus of a clinical study. Interventions include drugs, medical devices, procedures, vaccines, and other products that are either investigational or already available. Interventions can also include noninvasive approaches, such as education or modifying diet and exercise.
Experimental: OA-enriched Olive Oil

Participants will consume 55 mL/day of olive oil enriched with oleanolic acid (600 mg/kg) for 12 months, preferably raw and distributed across the three main meals.
Dietary supplement: Oleanolic acid-enriched olive oil

Olive oil enriched with oleanolic acid (600 mg/kg), 55 mL/day for 12 months, consumed preferably raw and distributed across the three main meals.
Experimental: Pomace Olive Oil

Participants will consume 55 mL/day of commercial pomace olive oil, which naturally contains oleanolic acid (180 mg/kg) and erythrodiol (670 mg/kg), for 12 months, preferably raw and distributed across the three main meals.
Dietary supplement: Pomace olive oil

Commercial pomace olive oil, naturally containing oleanolic acid (180 mg/kg) and erythrodiol (670 mg/kg), 55 mL/day for 12 months, consumed preferably raw and distributed across the three main meals.
Placebo Comparator: Control Olive Oil

Participants will consume 55 mL/day of commercial olive oil 0.4°, which has the same fatty acid composition but a very low content of minor bioactive components, for 12 months, preferably raw and distributed across the three main meals.
Dietary supplement: Commercial olive oil 0.4 degrees

Commercial olive oil 0.4°, with the same fatty acid composition but a very low content of minor bioactive components, 55 mL/day for 12 months, consumed preferably raw and distributed across the three main meals.

What is the study measuring?

Primary Outcome Measures

Primary Outcome Measures

In a clinical study's protocol, the planned outcome measure that is the most important for evaluating the effect of an intervention/treatment. Most clinical studies have one primary outcome measure, but some have more than one.
Outcome Measure
Measure Description
Time Frame
Conversion from prodromal Alzheimer's disease to dementia
Time Frame: Baseline to 12-months

Proportion of participants converting to dementia, defined as a change in the Clinical Dementia Rating Global Score (CDR-GS) from 0.5 at baseline to 1 or higher. The CDR-GS ranges from 0 to 3, with higher scores indicating greater dementia severity
Baseline to 12-months

Secondary Outcome Measures

Secondary Outcome Measures

In a clinical study's protocol, a planned outcome measure that is not as important as the primary outcome measure for evaluating the effect of an intervention but is still of interest. Most clinical studies have more than one secondary outcome measure.
Outcome Measure
Measure Description
Time Frame
Change in Clinical Dementia Rating Sum of Boxes (CDR-SB)
Time Frame: Baseline to 12-months

CDR-SB total score ranges from 0 to 18, with higher scores indicating more severe cognitive impairment.
Baseline to 12-months
Change in Mini-Mental State Examination (MMSE) score
Time Frame: Baseline to 12-months

MMSE total score ranges from 0 to 30, with higher scores indicating better global cognitive performance
Baseline to 12-months
Change in Mild Behavioral Impairment Checklist (MBI-C) score
Time Frame: Baseline to 12-months

MBI-C assesses behavioral and psychological symptoms; higher scores indicate more severe symptoms
Baseline to 12-months
Change in Functional Activities Questionnaire (FAQ) score
Time Frame: Baseline to 12-months

FAQ total score ranges from 0 to 30, with higher scores indicating greater functional impairment
Baseline to 12-months

Other Outcome Measures

Other Outcome Measures

For clinical trials, a planned measurement described in the protocol that is used to determine the effect of an intervention/treatment on participants. For observational studies, a measurement or observation that is used to describe patterns of diseases or traits, or associations with exposures, risk factors, or treatment. Types of outcome measures include primary outcome measure and secondary outcome measure.
Outcome Measure
Measure Description
Time Frame
Change in lipid metabolism biomarkers
Time Frame: Baseline, 6 months and 12 months

Serum concentrations of total triglycerides, total cholesterol, LDL cholesterol, HDL cholesterol, apolipoprotein A1 and apolipoprotein B
Baseline, 6 months and 12 months
Change in glucose metabolism and insulin sensitivity biomarkers
Time Frame: Baseline, 6 months and 12 months

Plasma glucose, insulin, glycated hemoglobin (HbA1c), HOMA-IR index and Quantitative Insulin Sensitivity Check Index (QUICKI)
Baseline, 6 months and 12 months
Change in plasma lipid classes
Time Frame: Baseline and 12 months

Cholesterol esters, triglycerides, diglycerides, free cholesterol, monoglycerides, phospholipids and ceramides determined by HPLC-MS.
Baseline and 12 months
Change in oxidative stress markers
Time Frame: Baseline, 6 months and 12 months

Reduced and oxidized glutathione (GSH, GSSG), Nrf2 levels, activities of superoxide dismutase, catalase and heme oxygenase-1, reactive oxygen species production and malondialdehyde.
Baseline, 6 months and 12 months
Change in inflammation markers
Time Frame: Baseline, 6 months and 12 months

NF-kB p65 and proinflammatory cytokines (TNF-alpha and IL-1beta) measured in plasma or serum.
Baseline, 6 months and 12 months
Change in circulating advanced glycation end products and dicarbonyl compounds and parameters related to their metabolism
Time Frame: Baseline, 6 months and 12 months
Baseline, 6 months and 12 months
Change in blood biomarkers of Alzheimer's disease pathology
Time Frame: Baseline and 12 months

Plasma p-tau 217, neurofilament light chain (NFL), glial fibrillary acidic protein (GFAP), and the amyloid beta 42/40 ratio.
Baseline and 12 months
Serum concentrations of oleanolic acid and erythrodiol
Time Frame: Baseline, 6 months and 12 months
Baseline, 6 months and 12 months

Collaborators and Investigators

This is where you will find people and organizations involved with this study.

Sponsor

Sponsor

The organization or person who initiates the study and who has authority and control over the study.
Spanish National Research Council

Collaborators

Collaborators

An organization other than the sponsor that provides support for a clinical study. This support may include activities related to funding, design, implementation, data analysis, or reporting.
Universidad de Granada
Maimónides Biomedical Research Institute of Córdoba
Hospital Universitario Reina Sofia de Cordoba
Valme University Hospital
Universidad Pablo de Olavide

Study record dates

These dates track the progress of study record and summary results submissions to ClinicalTrials.gov. Study records and reported results are reviewed by the National Library of Medicine (NLM) to make sure they meet specific quality control standards before being posted on the public website.

Study Major Dates

Study Start (Estimated)

Study Start

The actual date on which the first participant was enrolled in a clinical study. The "anticipated" study start date is the date that the researchers think will be the study start date.
January 1, 2027

Primary Completion (Estimated)

Primary Completion

The date on which the last participant in a clinical study was examined or received an intervention to collect final data for the primary outcome measure. Whether the clinical study ended according to the protocol or was terminated does not affect this date. For clinical studies with more than one primary outcome measure with different completion dates, this term refers to the date on which data collection is completed for all the primary outcome measures. The "anticipated" primary completion date is the date that the researchers think will be the primary completion date for the study.
October 1, 2028

Study Completion (Estimated)

Study Completion

The date on which the last participant in a clinical study was examined or received an intervention/treatment to collect final data for the primary outcome measures, secondary outcome measures, and adverse events (that is, the last participant's last visit). The "anticipated" study completion date is the date that the researchers think will be the study completion date.
January 1, 2029

Study Registration Dates

First Submitted

First Submitted

The date on which the study sponsor or investigator first submitted a study record to ClinicalTrials.gov. There is typically a delay of a few days between the first submitted date and the record's availability on ClinicalTrials.gov (the first posted date).
September 22, 2026

First Submitted That Met QC Criteria

First Submitted That Met QC Criteria

The date on which the study sponsor or investigator first submits a study record that is consistent with National Library of Medicine (NLM) quality control (QC) review criteria. The sponsor or investigator may need to revise and submit a study record one or more times before NLM's QC review criteria are met. It is the responsibility of the sponsor or investigator to ensure that the study record is consistent with the NLM QC review criteria.
September 22, 2026

First Posted (Actual)

First Posted

The date on which the study record was first available on ClinicalTrials.gov after National Library of Medicine (NLM) quality control (QC) review has concluded. There is typically a delay of a few days between the date the study sponsor or investigator submitted the study record and the first posted date.
September 29, 2026

Study Record Updates

Last Update Posted (Actual)

Last Update Posted

The most recent date on which changes to a study record were made available on ClinicalTrials.gov. There may be a delay between when the changes were submitted to ClinicalTrials.gov by the study's sponsor or investigator (the last update submitted date) and the last update posted date.
September 29, 2026

Last Update Submitted That Met QC Criteria

Last Update Submitted That Met QC Criteria

The most recent date on which the study sponsor or investigator submitted changes to a study record that are consistent with National Library of Medicine (NLM) quality control (QC) review criteria. It is the responsibility of the sponsor or investigator to ensure that the study record is consistent with the NLM QC review criteria.
September 22, 2026

Last Verified

Last Verified

The most recent date on which the study sponsor or investigator confirmed the information about a clinical study on ClinicalTrials.gov as accurate and current. If a study with a recruitment status of recruiting; not yet recruiting; or active, not recruiting has not been confirmed within the past 2 years, the study's recruitment status is shown as unknown.
September 1, 2026

More Information

Terms related to this study

Keywords

Other Study ID Numbers

Other Study ID Numbers

Identifiers or ID numbers other than the NCT number that are assigned to a clinical study by the study's sponsor, funders, or others. These numbers may include unique identifiers from other trial registries and National Institutes of Health grant numbers.
  • PID2024-161189OB-I00

Plan for Individual participant data (IPD)

Plan to Share Individual Participant Data (IPD)?

YES

IPD Plan Description

De-identified individual participant data underlying published results will be made available in institutional repositories, in accordance with the data management plan of the project and with international standards for the documentation of clinical study data.

IPD Sharing Time Frame

Data will become available after completion of the project and publication of the main results, and will remain accessible for at least five years thereafter.

IPD Sharing Access Criteria

Requests for access should be submitted to the principal investigator by e-mail, including a description of the proposed research question and analysis plan. Requests will be evaluated by the study investigators. Access to de-identified individual participant data and to the supporting documents will be granted to researchers whose proposal is considered methodologically sound and consistent with the consent given by study participants, subject to a signed data access agreement.

IPD Sharing Supporting Information Type

  • STUDY_PROTOCOL
  • ICF

Drug and device information, study documents

Studies a U.S. FDA-regulated drug product

No

Studies a U.S. FDA-regulated device product

No

This information was retrieved directly from the website clinicaltrials.gov without any changes. If you have any requests to change, remove or update your study details, please contact register@clinicaltrials.gov. As soon as a change is implemented on clinicaltrials.gov, this will be updated automatically on our website as well.

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