Polyphenols in olive oil

This page explains what polyphenols are, why they occur in olive oil, and what their content tells you about an oil's composition. If you arrived from a social post — welcome. No prior knowledge required.

What are polyphenols?

Polyphenols are a large group of organic compounds produced naturally in plants. They function as the plant's own defence system against sun, pests, and oxidation — a chemical protection mechanism found in leaves, bark, seeds, and fruit.

In the olive tree, polyphenols are concentrated in the leaves and the olive itself. When olives are pressed into oil, some of the polyphenols dissolve into the fat and carry through to the final product. Which ones, and how many, depends on the cultivar, the stage of ripeness, and how the pressing is handled.

Which polyphenols occur in olive oil?

Olive oil contains several subgroups of polyphenols. The most studied belong to the secoiridoids — a type of compound specific to the olive family (Oleaceae):

Oleocanthal — responsible for the characteristic peppery burning sensation in the throat, and the compound most studied for its chemical similarity to ibuprofen (see /fact/oleocanthal/).
Oleuropein and its derivatives — the dominant polyphenol compound in the olive fruit itself and the primary source of bitterness in the oil (see /fact/oleuropein/).
Hydroxytyrosol and tyrosol — simpler polyphenol compounds formed when oleuropein breaks down during pressing and storage. These, together with the oleuropein complex, are the specific compounds referenced in the EU-authorised EFSA health claim on blood lipids and oxidative stress (see /fact/polyphenols-and-oxidative-stress/).

Why the content varies so much

Polyphenol content can differ tenfold between a standard supermarket oil and a carefully handled early-harvest oil. It depends on an interplay of factors:

Cultivar. Different olive varieties produce polyphenols in different quantities. Lastovka, the cultivar grown at Vela Luka on Korčula, is known for consistently high polyphenol values.

Harvest timing. Content is highest in unripe, green olives early in the season. As the olive ripens, polyphenol content falls — while yield rises. Early harvests give lower volume but more polyphenol-rich oil.

Time from harvest to press. Polyphenols begin to degrade immediately after harvest. Every hour of delay is an hour of breakdown. Vala Selection's olives are pressed within 24 hours of harvest — not a marketing claim but a production decision that directly affects the final value.

Storage. Light, heat, and contact with air continue to break down polyphenols in the finished oil. Dark glass and correct storage slow the process.

What the numbers mean in context

Polyphenol content is measured in milligrams per kilogram of oil (mg/kg) using HPLC analysis. Observed ranges in the market:

100–250 mg/kg    ordinary olive oil
250–350 mg/kg    premium olive oil
700+ mg/kg       Vala Selection Core (guaranteed minimum per harvest)
1000+ mg/kg      Vala Selection Pre-harvest (target value)

Vala Selection's reference batch 2025-VL-MIR-001 measured at 1,004 mg/kg by HPLC analysis at the University of Split. That is a measured value for a specific batch — not an average and not a guarantee for every future harvest. Polyphenol content varies with harvest year and weather; each batch is analysed separately.

What this does not mean

High polyphenol content is a compositional measure — it describes what is in the oil, not what happens in the body. Polyphenols in olive oil are food components, not pharmaceuticals or dietary supplements.

The only EFSA-authorised health claim for olive oil polyphenols relates to the protection of blood lipids from oxidative stress, and it is strictly conditional. See /fact/polyphenols-and-oxidative-stress/ for a full account of what the claim says and does not say.

No food product — including high-polyphenol olive oil — may be marketed as a treatment for a disease.

How is polyphenol content measured?

The method is called HPLC — high-performance liquid chromatography. A full explanation of how the analysis works and what a value in mg/kg actually represents is at /fact/hplc-analysis/.