Olive Oil Polyphenols: What Lies Behind These Plant Compounds

Extra virgin olive oil is regarded as the flagship of the Mediterranean diet, and part of its reputation goes back to the polyphenols it contains. These secondary plant compounds give a good oil its typical, slightly bitter character that tickles the throat. There are many half-truths surrounding olive oil polyphenols, which is why in this guide we objectively explain what polyphenols in olive oil actually are, where they occur, how they enter the body and what European legislation permits to be said about them. This way you can better judge what matters when choosing a high-quality oil.

What are olive oil polyphenols?

Polyphenols are a large group of plant compounds that many plants form to protect against environmental influences. In olive oil these include above all substances such as hydroxytyrosol, tyrosol and the so-called oleuropein complex as well as oleocanthal, which is partly responsible for the slight tickle in the throat. Together they form the characteristic aroma profile of a good virgin oil.

The polyphenol content varies considerably, however. It depends on the olive variety, the degree of ripeness at harvest, the growing region, the processing and the storage. Early-harvested, green olives generally provide more polyphenols than fully ripe fruit. Gentle processing is also decisive, because heat and oxygen break down the sensitive compounds. This is why virgin oils from the first, cold pressing contain considerably more polyphenols than refined oils.

It is worth distinguishing polyphenols from monounsaturated fatty acids, which make up the largest part of olive oil. Both belong to the overall picture of a good oil but are different things. While the fatty acid content is fairly similar across all olive oils, it is the polyphenol content in particular that distinguishes an aromatic, freshly pressed virgin oil from a mild standard oil. Anyone who deliberately chooses an oil by its character thereby indirectly also opts for a certain level of polyphenols.

The authorised EU claim for olive oil polyphenols

For olive oil polyphenols there is a health claim examined and authorised by the European Union. It reads in the exact wording: Olive oil polyphenols contribute to the protection of blood lipids from oxidative stress. This claim may only be used if an oil meets the specified conditions.

The prerequisite is a daily intake of 20 grams of olive oil providing at least 5 milligrams of hydroxytyrosol and its derivatives, such as the oleuropein complex and tyrosol. Only oils with a correspondingly high polyphenol content can provide this amount in 20 grams at all. The claim expressly refers to the protection of blood lipids from oxidative stress and not to other effects. Other health-related statements about olive oil polyphenols are not legally authorised and should therefore be viewed critically.

Occurrence and content in different oils

Not every olive oil contains the same amount of polyphenols. As a rough order of magnitude the following applies:

• Extra virgin olive oil: from the first, cold processing, generally with the highest polyphenol content.
• Virgin olive oil: also unrefined, but often with a somewhat lower content.
• Refined or mild olive oil: polyphenol content greatly reduced by the processing.

A sensory indication of a high polyphenol content is the taste: an oil that tastes fruity-bitter and tickles the throat slightly is usually richer in these compounds than a very mild oil. Some producers have the polyphenol content analysed and state values in milligrams per kilogram. Such information helps with comparison but is not yet the rule in the trade.

When shopping, a few pointers on the label can help you. The designation extra virgin olive oil is the highest grade and already a good starting point. Information on origin, olive variety and harvest year indicates a producer who values transparency. A dark bottle protects the oil from light and also speaks for a well-thought-out product. If you have the chance to taste an oil, look for a fresh, green aroma and the typical slight bitterness rather than a completely neutral taste.

How polyphenols are absorbed

For olive oil polyphenols to play their role in the body, they must first be absorbed. Hydroxytyrosol and related compounds are considered readily available but are metabolised relatively quickly in the body. What is decisive, therefore, is not a single large amount so much as regular intake through the daily diet.

In everyday life this is easy to implement by using extra virgin olive oil as the main fat source, for example for salads, to refine vegetables or over ready-cooked dishes. Since strong heat breaks down the polyphenols, a high-quality oil shows its advantage especially in cold cuisine or when added only after cooking. This preserves a larger part of the sensitive plant compounds.

Olive oil within the Mediterranean diet

Olive oil polyphenols are often considered in isolation, yet their reputation is closely linked to the Mediterranean diet as a whole. In this way of eating, virgin olive oil is the central fat source, combined with plenty of vegetables, legumes, fruit, nuts, whole grains, fish and a rather restrained use of red meat and heavily processed products. Here the polyphenols are one building block among many, not an extra acting in isolation.

This explains why it makes little sense to overvalue a single food. Anyone who uses extra virgin olive oil but otherwise eats little vegetables and many heavily processed dishes hardly gets the most out of the framework in which Mediterranean cuisine gained its reputation. Conversely, a good oil fits seamlessly into an already plant-focused cuisine and replaces less favourable fats there. It is precisely in this role as a deliberately chosen, high-quality fat source that the oil's practical value in everyday life lies.

Storage and freshness

Polyphenols are sensitive to light, heat and oxygen. So that a high-quality oil retains its content for as long as possible, storage plays an important role. Keep olive oil cool, dark and well sealed, ideally in a dark glass bottle or canister and not right next to the stove. Opened bottles should be used up within a few months, since the polyphenol content decreases over time and the oil can turn rancid.

An indication of freshness is the harvest year or the bottling date on the bottle. The fresher the oil, the more of the sensitive plant compounds are generally still present. An already rancid oil with a musty or off smell has lost much of its quality and should no longer be used.

Honestly assessed

Olive oil polyphenols are a good example of the fact that a food is more than its calories. The authorised EU claim, however, expressly refers only to the protection of blood lipids from oxidative stress and applies bound to the stated amount and minimum content. Further healing promises around olive oil are not legally covered and not factually substantiated.

What remains decisive is the overall picture of the diet. A high-quality extra virgin olive oil fits well into a balanced, plant-focused diet but replaces neither vegetables, whole grains and legumes nor an overall healthy lifestyle. Anyone who has health questions or suffers from an illness should discuss these with their doctor and not orient their diet around a single food alone.

The amount should also be kept in mind, because olive oil is very energy-rich despite its valued composition. It therefore makes little sense to use ever larger amounts for the sake of the polyphenols alone. It is more sensible to use high-quality oil specifically where it gives its best in terms of taste and nutrition and to cut back on other, less favourable fats in return. This way the oil fits moderately into a balanced diet instead of making it unnecessarily higher in calories.

Frequently Asked Questions (FAQ)

What are polyphenols in olive oil?

Polyphenols are secondary plant compounds, in olive oil above all hydroxytyrosol, tyrosol, the oleuropein complex and oleocanthal. They shape the typically bitter, throat-tickling taste of a good virgin oil.

What is one allowed to say about olive oil polyphenols according to the EU?

Authorised is the claim: Olive oil polyphenols contribute to the protection of blood lipids from oxidative stress. The prerequisite is 20 grams of oil daily with at least 5 milligrams of hydroxytyrosol and its derivatives.

Which oil has the most polyphenols?

As a rule, extra virgin olive oil from the first, cold processing contains the most polyphenols. Refined or very mild oils have considerably less of these plant compounds due to the processing.

Does heating destroy the polyphenols?

Strong heat and prolonged heating break down part of the sensitive polyphenols. This is why a high-quality oil comes into its own especially in cold cuisine or added only after cooking.

How do I store olive oil correctly?

Cool, dark and well sealed, best in dark glass and not next to the stove. Use up opened bottles within a few months, since polyphenol content and freshness decrease over time.