Hydroxytyrosol Dietary Supplement and Prevention of Age-Related Diseases

Fifty subjects 40-75 years old overweight (BMI between 24-29,9 kg/m2) and prediabetes (fasting blood sugar between 100-126 mg/dl and/or glycated hemoglobin between 5,7-6,4%) will be recruited. Detailed inclusion and exclusion criteria are provided below.

Participants will be randomly divided into two groups, one to consume the Hytolive® capsule and the other a placebo. The intervention study has been designed for daily consumption before breakfast of one capsule for 16 weeks. The study includes a two-week washout period during which subjects will not be allowed to consume olives or virgin olive oil.

At the beginning and end of the study, upon arrival at the ICTAN-CSIC Human Nutrition Unit, volunteers will provide a urine sample corresponding to the first morning void, and a nurse will draw a fasting blood sample (20 mL distributed in tubes with various anticoagulants for measurements). Additionally, their blood pressure will be measured, and a complete anthropometric and body composition study will be conducted. Furthermore, volunteers will provide a stool sample from the preceding days (these samples will not be used in this study but will be stored at -80°C for potential future determination of the intestinal microbiota metagenomic profile). Subsequently, dietary controls will be conducted, physical activity and emotional well-being tests will be administered, and fatigue will be evaluated. Additionally, there will be an interim visit aimed at verifying adherence to supplementation. For this purpose, volunteers will provide a urine sample corresponding to the first morning void on an empty stomach, in which levels of hydroxytyrosol and its derivatives will be determined. Likewise, dietary and physical activity controls will be conducted to confirm that volunteers are not altering their habits.

• Group 1, hydroxytyrosol-rich extract capsule (Dietary supplement): Following a two-week washout period, the subjects will receive a bottle containing capsules (Group 1). Blood, urine, and fecal samples will be collected from each participant during their stay at the Human Nutrition Unit at the beginning and end of the study. Subjects will be instructed to refrain from consuming products rich in hydroxytyrosol (such as virgin olive oil and olives) and to maintain their usual dietary habits throughout the study. Additionally, olive oil (1L/week) will be provided to each volunteer that will consume during intervention study as the sole source of dietary fat, used for cooking, salad dressing, toasts, etc. in order to control the extra consumption of hydroxytyrosol apart from that provided by the capsule.
• Group 2, capsule of placebo (Dietary supplement): Following a two-week washout period, the subjects will receive a bottle containing capsules (Placebo) (Group 2). Blood, urine, and fecal samples will be collected from each participant during their stay at the Human Nutrition Unit at the beginning and end of the study. Subjects will be instructed to refrain from consuming products rich in hydroxytyrosol (such as virgin olive oil and olives) and to maintain their usual dietary habits throughout the study. Additionally, olive oil (1L/week) will be provided to each volunteer that will consume during intervention study as the sole source of dietary fat, used for cooking, salad dressing, toasts, etc. in order to control the extra consumption of hydroxytyrosol.

Primary outcomes

• LDL-ox as marker of oxidative status [Up to six months]: Differences between subjects supplemented with hydroxytyrosol and non-supplemented subjects

Secondary outcomes

• Mental well-being determined by Warwick-Edinburgh Mental Well-being Scale [Up to two months]: Differences between subjects supplemented with hydroxytyrosol and no-supplemented subjects
• Sleep quality determined by Pittsburgh Sleep Quality Index [Up to two months]: Differences between subjects supplemented with hydroxytyrosol and no-supplemented subjects
• Fatigue test determined by Borg Rating Of Perceived Exertion [Up to two months]: Differences between subjects supplemented with hydroxytyrosol and no-supplemented subjects
• Fasting glucose [Up to six months]: Differences between subjects supplemented with hydroxytyrosol and no-supplemented subjects
• Fasting insulin [Up to six months]: Differences between subjects supplemented with hydroxytyrosol and no-supplemented subjects
• Glycated hemoglobin (HbA1c) [Up to six months]: Differences between subjects supplemented with hydroxytyrosol and no-supplemented subjects
• Glucagon-like peptide-1 (GLP-1) [Up to six months]: Differences between subjects supplemented with hydroxytyrosol and no-supplemented subjects
• Total cholesterol [Up to six months]: Differences between subjects supplemented with hydroxytyrosol and no-supplemented subjects
• High density lipoproteins (HDL) [Up to six months]: Differences between subjects supplemented with hydrpxytyrosol and no-supplemented subjects
• Low density lipoproteins (LDL) [Up to six months]: Differences between subjects supplemented with hydroxytyrosol and no-supplemented subjects
• Triglycerides [Up to six months]: Differences between subjects supplemented with hydroxytyrosol and no-supplemented subjects
• Apoliporpotein A1 [Up to six months]: Differences between subjects supplemented with hydroxytyrosol and no-supplemented subjects
• Apoliporpotein B [Up to six months]: Differences between subjects supplemented with hydroxytyrosol and no-supplemented subjects
• Total antioxidant status (TAS) [Up to six months]: Differences between subjects supplemented with hydroxytyrosol and no-supplemented subjects
• Total oxidative status (TOS) [Up to six months]: Differences between subjects supplemented with hydroxytyrosol and no-supplemented subjects
• Oxides of nitrogen (NOx) [Up to six months]: Differences between subjects supplemented with hydroxytyrosol and no-supplemented subjects
• Thiobarbituric acid reactive substances (TBARS) [Up to six months]: Differences between subjects supplemented with hydroxytyrosol and no-supplemented subjects
• C reactive protein [Up to six months]: Differences between subjects supplemented with hydroxytyrosol and no-supplemented subjects
• Interleukine 6 (IL-6) [Up to six months]: Differences between subjects supplemented with hydroxytyrosol and no-supplemented subjects
• Tumor necrosis factor alpha (TNF-α) [Up to six months]: Differences between subjects supplemented with hydroxytyrosoland no-supplemented subjects
• Alanine aminotransfesare (transaminases ALT) [Up to six months]: Differences between subjects supplemented with hydroxytyrosol and no-supplemented subjects
• Aspartate aminotransferase (transaminase AST) [Up to six months]: Differences between subjects supplemented with hydroxytyrosol and no-supplemented subjects

Sex: All, ages: 40 Years to 75 Years, accepts healthy volunteers

Inclusion Criteria:

* Prediabetes (defined as fasting glucose levels according to the American Diabetes Association guideline, with fasting blood glucose ≥100 and <126 mg/dL, or hemoglobin A1c levels ranging from 5.7% to 6.4%)
* Overweight (body mass index BMI 24-29.9 kg/m2)

Exclusion Criteria:

* Any prior diagnosis of diabetes, hypertension, hyperlipidemia, other cardiovascular diseases, thyroid gland disorders, asthma, arthritis, or inflammatory conditions, cirrhosis, or other liver diseases
* Weight loss > 2.5 kg in the last 6 months
* Being on pharmacological treatment of any kind
* Taking dietary supplements containing antioxidants other than vitamins
* Being a smoker or habitual alcohol consumer; being HIV positive
* Being pregnant or breastfeeding
* Blood pressure ≥ 140 mmHg (systolic) and ≥ 90 mmHg (diastolic)
* Total cholesterol ≥ 240 mg/dL, LDL cholesterol ≥ 160 mg/dL, or TG ≥ 200 mg/dl

• Results publication: Moratilla-Rivera I, Perez-Jimenez J, Ramos S, Portillo MP, Martin MA, Mateos R. Hydroxytyrosol supplementation improves antioxidant and anti-inflammatory status in individuals with overweight and prediabetes: A randomized, double-blind, placebo-controlled parallel trial. Clin Nutr. 2025 Sep;52:17-26. doi: 10.1016/j.clnu.2025.07.006. Epub 2025 Jul 12. PMID 40690822

• Raquel Mateos, PhD, Principal investigator, Institute of Food Science, Technology and Nutrition (ICTAN-CSIC)