Hydroxytyrosol: Which Olive Oils Have the Most, and What the Numbers Mean
Which olive oil has the highest hydroxytyrosol content? It is a fair question, and the honest answer starts with a correction: almost none of the hydroxytyrosol in a fresh extra virgin olive oil is sitting there as free hydroxytyrosol. Most of it is bound up in larger molecules — oleacein and the oleuropein aglycones — and how much of that a laboratory reports depends on which method it used and which compounds it chose to add up. So the oils with the most hydroxytyrosol are real and identifiable, but the numbers attached to them are not all measuring the same thing. This guide sets out what the EU's one authorised claim actually requires, how laboratories measure it, what peer-reviewed research says raises and lowers it, and how to read the figures brands publish.
For our own oil, see our Cold-Pressed Single-Estate Extra Virgin Olive Oil - Marrakech (500ml).
The Short Answer
- The one legal benchmark is 5 mg per 20 g. Regulation (EU) No 432/2012 allows the claim that olive oil polyphenols contribute to the protection of blood lipids from oxidative stress only for olive oil containing at least 5 mg of hydroxytyrosol and its derivatives (e.g. oleuropein complex and tyrosol) per 20 g of oil.
- Free hydroxytyrosol is a small fraction of the total. One brand's 2025 laboratory report from Laboratorio Espejo in Seville lists 438 mg/kg of total biophenols but just 2 mg/kg of free hydroxytyrosol — most of the phenolic content sits in larger, bound molecules.
- Method changes the number. An inter-laboratory study by Tsimidou and colleagues, testing the same oils with five liquid chromatography protocols and one NMR protocol, found differences in absolute values between methods.
- Cultivar matters most. In a 2021 study of 44 widespread cultivars over three seasons, Miho and colleagues found up to 15-fold differences in total phenols, with cultivar explaining 66.8% of the variance.
- Earlier harvest raises it; time lowers it. A 160-oil study found total phenols fell by about 42% after 12 months' dark storage at 20 °C, while free hydroxytyrosol actually rose as the larger molecules broke down.
- Read the certificate, not the headline. A useful figure names the laboratory, the date, the sample and the method — and says which compounds were added together.
- We do not publish a hydroxytyrosol figure for our own oil, because no laboratory result for the current batch is on file. We will not imply one.
What Hydroxytyrosol Is — and Why Most of It Is Hidden
Hydroxytyrosol is a small phenolic molecule that olive trees build into much larger ones. In the fruit it sits inside oleuropein; when the olives are crushed at the mill, enzymes break oleuropein down into new compounds — oleacein and the aldehydic forms of oleuropein aglycone — each of which still carries a hydroxytyrosol unit. A parallel family descends from ligstroside and carries tyrosol instead; oleocanthal belongs to that side, as our article on oleocanthal explains.
That is why "hydroxytyrosol content" can mean three different numbers. There is free hydroxytyrosol, the small molecule on its own. There are hydroxytyrosol derivatives, the bound forms such as oleacein, oleuropein aglycone and hydroxytyrosol acetate. And there is the total you get if a laboratory breaks every bound form apart and counts the hydroxytyrosol released. In a fresh oil the first figure is usually tiny and the second is large. Our guide to olive oil polyphenols walks through the wider family.
The One Authorised Claim, Word for Word
We read the annex to Commission Regulation (EU) No 432/2012 on legislation.gov.uk on 3 October 2026, in its latest available revised form. The entry for olive oil polyphenols permits the wording "Olive oil polyphenols contribute to the protection of blood lipids from oxidative stress". Its conditions of use read: "The claim may be used only for olive oil which contains at least 5 mg of hydroxytyrosol and its derivatives (e.g. oleuropein complex and tyrosol) per 20 g of olive oil. In order to bear the claim information shall be given to the consumer that the beneficial effect is obtained with a daily intake of 20 g of olive oil." The entry cites the EFSA Journal 2011;9(4):2033 as its scientific basis.
Three details are worth noticing. The condition is written per 20 g of oil, not per kilogram. It names hydroxytyrosol and its derivatives, so free hydroxytyrosol alone is the wrong figure to compare against it. And its examples include tyrosol, which is why some laboratories add tyrosol-side compounds into the sum and others do not.
If you want to compare a certificate written in mg/kg, the arithmetic is simple: 20 g is one-fiftieth of a kilogram, so 5 mg per 20 g is the same ratio as 250 mg per kg. That is our conversion, not the regulation's wording — and it applies only to hydroxytyrosol and its derivatives, never to a total-polyphenol figure. Our guide to high phenolic olive oil explains why those two numbers must not be swapped.
| What the regulation says | What it means for a certificate |
|---|---|
| At least 5 mg of hydroxytyrosol and its derivatives per 20 g of olive oil | Divide a mg/kg result for that fraction by 50 to get mg per 20 g |
| Examples given: oleuropein complex and tyrosol | Check whether the laboratory's sum includes tyrosol-side compounds |
| Consumer told the effect comes with 20 g a day | The claim is about a daily amount of oil, not a single serving |
| No figure in mg/kg; no mention of total polyphenols | A total-biophenol figure is a different measurement |
How Laboratories Measure It: HPLC, NMR and Hydrolysis
The International Olive Council method COI/T.20/Doc. No 29 uses high-performance liquid chromatography (HPLC) to separate the phenolic compounds and report a total biophenols figure, expressed as tyrosol. It also lets a laboratory list individual peaks — free hydroxytyrosol, tyrosol, oleacein, oleocanthal — which is how a single certificate can show a large total and a tiny free hydroxytyrosol line side by side.
Quantitative NMR, developed by Karkoula, Skantzari, Melliou and Magiatis at the University of Athens, measures the main secoiridoids directly. Their 2012 method measured oleocanthal and oleacein in 175 Greek and Californian oils; a 2014 extension added the monoaldehydic oleuropein and ligstroside aglycones across 340 oils from 23 varieties, where the sum of the four ranged from undetectable to 1,534 mg/kg [1][2]. NMR certificates often report "total hydroxytyrosol derivatives" and "total tyrosol derivatives" as separate lines.
Hydrolysis methods take a third route: they break the bound forms apart and measure the hydroxytyrosol and tyrosol released, which maps neatly onto the wording of the claim. Tsimidou and colleagues compared five liquid chromatography protocols and one NMR protocol across five expert laboratories, analysing the same authentic oils within three months, and found slight to statistically significant differences in absolute values between methods [3].
Older colorimetric tests are less useful here. Castillo-Luna and Priego-Capote, testing 100 extra virgin olive oils in 2026, found the classic Folin-Ciocalteu method non-selective and prone to underestimating real phenolic content [4].
| Method | What it reports | What to watch for |
|---|---|---|
| HPLC, IOC COI/T.20/Doc. No 29 | Total biophenols as tyrosol, plus individual compounds | The total is not the claim fraction; free hydroxytyrosol is only one line |
| Quantitative 1H NMR | Oleocanthal, oleacein and the oleuropein and ligstroside aglycones directly | Check whether tyrosol derivatives are added into the per-20 g sum |
| Hydrolysis then chromatography | Total hydroxytyrosol and tyrosol released from bound forms | Closest to the claim wording; results still differ between protocols |
| Folin-Ciocalteu (colorimetric) | A general phenol reading | Non-selective; not suitable for the claim |
Which Olive Oils Have the Most? What the Research Shows
No brand name answers this question on its own. Peer-reviewed work points to four levers, and the oils that score highest tend to combine them.
Cultivar comes first. Miho and colleagues analysed oils from 44 of the most widespread cultivars, evaluated homogeneously over three consecutive seasons, and found up to 15-fold differences in total phenol concentration; cultivar explained 66.8% of the variance [5]. Varieties such as Koroneiki and Coratina have reputations for robust oils, and our cultivar articles cover them individually.
Harvest timing comes next. In the 2012 NMR study, higher oleocanthal and oleacein levels correlated with earlier harvest [1]. In Cornicabra oils studied by Gómez-Rico and colleagues over two seasons, the main hydroxytyrosol secoiridoid fell from 770 to 450 mg/kg as the fruit ripened under rain-fed conditions, and hydroxytyrosol derivatives fell more than tyrosol derivatives [6]. Our guide to early harvest olive oil covers the trade-off in yield and flavour.
Water supply plays a part. The same Cornicabra study found that more irrigation lowered secoiridoid content: at a similar ripeness, that compound fell from 676 mg/kg in rain-fed trees to 388 mg/kg under the FAO-recommended irrigation regime [6]. That is one cultivar in one region, not a rule that every rain-fed oil is high.
Scale tells you what is typical. Diamantakos and colleagues analysed 5,764 Greek oils from more than 30 varieties over eleven years by NMR. The mean total phenolic content was 483 mg/kg and the highest recorded was 4,003 mg/kg; they also found a significant correlation with harvest period and identified varieties giving higher figures [7].
Storage: The Number Falls — and Free Hydroxytyrosol Rises
Phenolic compounds are consumed as an oil ages, which is part of what they are doing in the bottle. Castillo-Luna and colleagues stored 160 extra virgin olive oils in darkness at 20 °C for 12 months and found the phenolic concentration fell by 42.0% on average, with a wide spread (±24.3%) depending on each oil's starting profile [8]. Diamantakos and colleagues reported an average loss of 46% over 12 months of usual storage, and proposed that "high-phenolic" should mean above 500 mg/kg so that an oil can still meet the 250 mg/kg equivalent a year after bottling [7].
The counter-intuitive part is that free hydroxytyrosol goes up as an oil ages, because the larger secoiridoids break down and release it. Castillo-Luna's team suggested free hydroxytyrosol and oleocanthalic acid can act as markers of ageing [8]. So a high free hydroxytyrosol line on its own is not a sign of a fresh, phenol-rich oil — it can mean the opposite. Our article on expired olive oil covers the wider signs of age.
Reading Real Certificates: Two Published Examples
Here is what two brands publish, read directly from their own certificates on 3 October 2026. We report the figures as printed and draw no conclusion about which oil is better.
| Brand and oil | Laboratory, report, date | Total biophenols | Free hydroxytyrosol | Hydroxytyrosol and derivatives per 20 g |
|---|---|---|---|---|
| Blueprint Extra Virgin Olive Oil | Laboratorio Espejo, Seville; report A-46697/25, issued 28 November 2025 | 438 mg/kg (as tyrosol, IOC method) | 2 mg/kg | Not reported |
| Olivea Ultra High Phenolic EVOO | Multichrom Lab, Athens; certificate Π-127805, issued 4 November 2025 | 874 mg/kg (as tyrosol, IOC method) | Not reported on that certificate | Stated on Olivea's results page; not shown on the linked certificate |
| Sidr & Stone single-estate Marrakech | No laboratory result on file for the current batch | Not published | Not published | Not published |
The Blueprint report shows how small the free line can be next to the total. Neither line tells you, on its own, whether the oil meets the 5 mg per 20 g condition — that needs the derivatives measured. Olivea's results page states a per-20 g hydroxytyrosol figure, but the certificate it links reports total biophenols and a pesticide screen, so the document behind that figure is not the one we could open. Both brands publish more than most; the point is simply to match each number to its document.
A quick test for any certificate: find the laboratory's name, the issue date, the sample reference and the method; then check whether the line you care about is free hydroxytyrosol, a derivatives sum, or a total.
What the Human Evidence Supports
The claim rests on lipid-oxidation research, the best known being EUROLIVE. Covas and colleagues randomised 200 healthy men across six centres in five European countries to 25 mL a day of three olive oils — low (2.7 mg/kg), medium (164 mg/kg) and high (366 mg/kg) phenolic content — for three weeks each [9]. Markers of oxidative stress, including oxidised LDL, fell in line with phenolic content, and HDL cholesterol rose more with higher-phenol oil.
That is a real but narrow result: healthy men, short periods and blood markers rather than long-term health outcomes. It supports what the claim says — protection of blood lipids from oxidative stress — and nothing broader. A higher hydroxytyrosol figure does not make an olive oil a medicine.
The Objections Worth Taking Seriously
"Then the highest number on the shelf wins." Only if the numbers measure the same fraction, by the same method, at a similar age. A 2025 total-biophenol figure and a fresh NMR derivatives sum are not comparable, and both describe a sample on a date, not the bottle you open months later.
"Why not just take a hydroxytyrosol supplement?" That is a different product, and this article is about food. The authorised claim is written for olive oil at 20 g a day, eaten as part of a normal diet.
"You have no figure, so you would say that." Fair. We publish no hydroxytyrosol figure because the current batch has not been analysed, and the argument above rests on peer-reviewed studies and other brands' own certificates, not on our oil.
Why Sidr & Stone
An article about verification owes the reader a plain statement of our own position. Sidr & Stone's Cold-Pressed Single-Estate Extra Virgin Olive Oil - Marrakech (500ml) has no hydroxytyrosol or polyphenol figure on file, so we quote none. What we can state is how it is grown and made.
- Single-estate — Sidr & Stone's olive oil comes from our own family-owned farm on the plains outside Marrakech, Morocco, and we control every step from tree to bottle, with no blending across origins.
- Rain-fed — our trees are not irrigated; they take what the season gives.
- Organically grown — no synthetic fertilisers, pesticides or herbicides are used (not yet certified; certification is in progress).
- Single harvest — a small, limited batch, picked when the fruit is ready; the current batch's harvest details are on the product page.
- Cold-pressed within hours of harvest — mechanical extraction only, with no solvents, refining or deodorising.
- Unfiltered extra virgin — minimally processed, so it may show natural sediment, which is normal.
- 100% natural — a single ingredient, olive oil, with nothing added.
- Dark glass with a gold label — protective packaging against light, which matters for every phenolic compound in this article.
- 10% of profits to charity — a brand-wide Sidr & Stone commitment.
- Fulfilment in the UK, EU, and US.
We will not tell you ours is the olive oil with the most hydroxytyrosol — that is exactly the kind of claim this article asks you to check. When the current batch is analysed, the certificate will be published with the laboratory, date and method named, whatever it says.
Frequently Asked Questions
Which olive oil has the highest hydroxytyrosol content?
The highest figures come from robust cultivars picked early; in one study of 5,764 Greek oils the top total phenolic result was 4,003 mg/kg. Compare brands only on certificates that name the laboratory, date, method and the exact fraction measured.
What is the difference between hydroxytyrosol and its derivatives?
Free hydroxytyrosol is the small molecule on its own. Its derivatives, such as oleacein and oleuropein aglycone, carry a hydroxytyrosol unit inside a larger molecule, and in a fresh oil they make up most of the total.
How do I check whether an oil meets the 5 mg per 20 g condition?
Look for a certificate reporting hydroxytyrosol and its derivatives, then divide a mg/kg figure by 50 to get mg per 20 g. A total-biophenol figure or a free hydroxytyrosol line alone cannot answer the question.
Why does free hydroxytyrosol increase as olive oil ages?
Because the larger secoiridoid molecules break down during storage and release it. In a study of 160 oils stored for a year, free hydroxytyrosol rose while total phenols fell, so researchers suggested it can mark an older oil.
How does Sidr & Stone's olive oil compare?
We cannot compare figures, because we have not published one for the current batch. Ours is single-estate, rain-fed, organically grown, unfiltered and cold-pressed within hours of harvest; a certificate will be published once it exists.
Does cooking destroy hydroxytyrosol?
Heat, light, air and time all reduce phenolic compounds, so using some oil raw — on salads, bread or finished dishes — keeps more of them. Cooking with extra virgin olive oil is still a sound everyday choice.
Where can I buy a single-estate extra virgin olive oil?
Look for a producer that names one farm, one origin and a harvest, and bottles in dark glass. Ours is available to pre-order from our limited single-harvest batch, with fulfilment in the UK, EU, and US.
Is olive oil a medicine?
No. Olive oil is a food, not a medicine. It has a long traditional history — including being honoured in the Prophetic Sunnah — and a substantial body of modern research, particularly around polyphenols, cardiovascular health, and the Mediterranean diet pattern. It can be a worthwhile part of a healthy routine, but it does not cure diseases and is not a substitute for medical care. Be cautious of any olive oil marketed with specific disease-cure claims.
Final Thoughts
Hydroxytyrosol is one of the best-documented compounds in olive oil, and the only one tied to an authorised claim. That makes it worth caring about — and worth reading carefully, because the same oil can show 2 mg/kg on one line and several hundred on another, depending on whether the laboratory counted the free molecule, the bound forms or a total.
The research is consistent about where high figures come from: the right cultivar, picked early, stored cool and dark, and eaten while fresh. Brand names come second. Ask for the certificate, check the date and method, and divide by 50 if you want the per-20 g figure. For the wider checks on any bottle, our guide to choosing a quality olive oil is a good next step.
Our Cold-Pressed Single-Estate Extra Virgin Olive Oil - Marrakech (500ml) — rain-fed, organically grown and unfiltered — is available to pre-order now from our limited single-harvest batch, with fulfilment in the UK, EU, and US.
Our extra virgin olive oil is grown organically on our own single-estate farm on the plains outside Marrakech: we control every step from tree to bottle, and no synthetic pesticides, herbicides or fertilisers are used. It is not yet certified organic — certification is in progress, and we will publish it as soon as it comes through.
References
- Karkoula E, Skantzari A, Melliou E, Magiatis P. Direct measurement of oleocanthal and oleacein levels in olive oil by quantitative (1)H NMR. Establishment of a new index for the characterization of extra virgin olive oils. J Agric Food Chem. 2012;60(47):11696-11703. doi:10.1021/jf3032765. PMID 23116297
- Karkoula E, Skantzari A, Melliou E, Magiatis P. Quantitative measurement of major secoiridoid derivatives in olive oil using qNMR. Proof of the artificial formation of aldehydic oleuropein and ligstroside aglycon isomers. J Agric Food Chem. 2014;62(3):600-607. doi:10.1021/jf404421p. PMID 24384036
- Tsimidou MZ, Nenadis N, Mastralexi A, Servili M, Butinar B, Vichi S, Winkelmann O, García-González DL, Toschi TG. Toward a Harmonized and Standardized Protocol for the Determination of Total Hydroxytyrosol and Tyrosol Content in Virgin Olive Oil (VOO). The Pros of a Fit for the Purpose Ultra High Performance Liquid Chromatography (UHPLC) Procedure. Molecules. 2019;24(13):2429. doi:10.3390/molecules24132429. PMID 31269664
- Castillo-Luna A, Priego-Capote F. Absolute Quantitation of Phenolic Compounds in Olive Oil for Health Claim Recognition. Antioxidants (Basel). 2026;15(4):511. doi:10.3390/antiox15040511. PMID 42072153
- Miho H, Moral J, Barranco D, Ledesma-Escobar CA, Priego-Capote F, Díez CM. Influence of genetic and interannual factors on the phenolic profiles of virgin olive oils. Food Chem. 2021;342:128357. doi:10.1016/j.foodchem.2020.128357. PMID 33508902
- Gómez-Rico A, Salvador MD, La Greca M, Fregapane G. Phenolic and volatile compounds of extra virgin olive oil (Olea europaea L. Cv. Cornicabra) with regard to fruit ripening and irrigation management. J Agric Food Chem. 2006;54(19):7130-7136. doi:10.1021/jf060798r. PMID 16968073
- Diamantakos P, Ioannidis K, Papanikolaou C, Tsolakou A, Rigakou A, Melliou E, Magiatis P. A New Definition of the Term "High-Phenolic Olive Oil" Based on Large Scale Statistical Data of Greek Olive Oils Analyzed by qNMR. Molecules. 2021;26(4):1115. doi:10.3390/molecules26041115. PMID 33669887
- Castillo-Luna A, Criado-Navarro I, Ledesma-Escobar CA, López-Bascón MA, Priego-Capote F. The decrease in the health benefits of extra virgin olive oil during storage is conditioned by the initial phenolic profile. Food Chem. 2021;336:127730. doi:10.1016/j.foodchem.2020.127730. PMID 32768900
- Covas MI, Nyyssönen K, Poulsen HE, et al.; EUROLIVE Study Group. The effect of polyphenols in olive oil on heart disease risk factors: a randomized trial. Ann Intern Med. 2006;145(5):333-341. doi:10.7326/0003-4819-145-5-200609050-00006. PMID 16954359
Disclaimer: This article describes published research, analytical methods, the text of Regulation (EU) No 432/2012 as read on legislation.gov.uk, and brands' own published laboratory certificates as checked on 3 October 2026; regulations, methods, products and test results may change, and readers should check current sources. Figures attributed to named brands are taken from those brands' own published documents and reported as printed. References to named brands describe publicly available information and are not affiliated with or endorsed by them. Comparisons are made in good faith and in fair terms. Olive oil is a food, not a medicine, and is not a substitute for medical treatment of any condition. For any health concern, consult a qualified medical professional.