How we rate
“Strong” = several concordant meta-analyses or systematic reviews. “Moderate” = one synthesis, or several controlled trials. “Limited” = early trials only. The rating is about the quality of the studies, not about how useful the supplement is.
Olive polyphenols (hydroxytyrosol)
Olive oil polyphenols, including hydroxytyrosol, slightly protect LDL (the "bad" cholesterol) from oxidation in small trials. EFSA and meta-analyses remain cautious regarding cholesterol, blood pressure, or weight.
Benefits
- Less oxidized LDL: in 18 healthy volunteers, 3 weeks of polyphenol-rich olive oil (366 mg/kg) reduced LDL oxidation, compared to a polyphenol-poor oil.
- An effect starting from small doses: biscuits enriched with 5.25 mg of hydroxytyrosol reduced postprandial oxidized LDL in 13 people; a review places the first effects on oxidized LDL starting from 10 mg per day.
- In overweight individuals with prediabetes: in 49 adults, 15 mg of hydroxytyrosol per day for 16 weeks reduced oxidized LDL, markers of oxidative damage, and IL-6, a marker of inflammation, without changing blood lipids or weight.
- A little more HDL: a meta-analysis of 10 trials found an increase in HDL-cholesterol at all tested doses of olive oil polyphenols; LDL only decreases at high doses.
- More effective HDL: in 47 men, 25 mL per day of polyphenol-rich oil for 3 weeks improved the cholesterol efflux capacity of HDL by 3 %.
- Fewer small LDL particles: in 25 healthy men, 25 mL per day of polyphenol-rich oil for 3 weeks reduced apoB-100 and the number of small LDL particles, compared to a poor oil.
- Total cholesterol, triglycerides, and insulin decreased in a meta-analysis of 14 trials (594 participants) on oleuropein, hydroxytyrosol, and tyrosol, especially in individuals already suffering from cardiometabolic diseases.
- Less knee pain: in people with knee osteoarthritis, 4 weeks of hydroxytyrosol improved pain scores compared to a placebo.
Precautions
Tolerance: 15 mg per day for 6 months was safe and well tolerated in 29 women; 45 mg per day for 8 weeks did not alter the liver, kidneys, or electrolytes in 14 people. Ferritin and folates: in the latter trial, ferritin and folates decreased. Limitations: EFSA (2025) considers the evidence insufficient to state that olive oil polyphenols maintain normal HDL-cholesterol: the increase seen in one study was not found elsewhere. Nor does EFSA (2025) acknowledge any established effect on LDL-cholesterol or systolic blood pressure. Alone, hydroxytyrosol has no significant effect on metabolic syndrome, in a meta-analysis of 67 trials. Weight: the weight and visceral fat loss seen after 4 weeks with 15 mg per day tapered off at 12 and 24 weeks. Trials are small (12 to 49 participants for the most part, 200 at most), often short, with highly variable doses and forms.
Recommended dosage
In trials: 5 to 45 mg of hydroxytyrosol per day, or 25 mL per day of a polyphenol-rich olive oil (366 mg/kg).
How to take it
- Form: trials use either a polyphenol-rich olive oil, or hydroxytyrosol in capsules or in an enriched food (biscuits).
- Dose: 15 mg of hydroxytyrosol per day in trials lasting 3 weeks to 6 months; 25 mL per day for the oil.
- Duration: from 1 week to 6 months depending on the trials.
- Rich or depleted oil: in a 3-month trial on 90 volunteers, only the polyphenol-rich oil (328 mg/kg) reduced oxidative stress and inflammation, not the depleted oil (55 mg/kg).
- Absorption: hydroxytyrosol from an enriched biscuit rapidly enters the blood, with a peak 0.5 to 1 hour after.
- What does not work: 5 or 25 mg per day for one week changed neither blood lipids, nor inflammation, nor markers of oxidation.
Did you know?
In 14 volunteers, 45 mg of hydroxytyrosol per day for 8 weeks doubled blood vitamin C levels, without changing cardiovascular markers.
What the studies say
This meta-analysis of 14 human intervention studies (594 participants) shows that oleuropein, hydroxytyrosol and tyrosol supplementation significantly reduces total cholesterol, triglycerides and insulin. The effects appear more marked in individuals with BMI <30, non-Mediterranean or suffering from cardiometabolic diseases. The authors call for additional studies to confirm these results.
Frumuzachi O, Kieserling H, Rohn S, Mocan A. — Critical reviews in food science and nutrition (2025) — View the source study
For information only: not a substitute for medical advice. Dietary supplements are not a replacement for a varied, balanced diet. Learn more