What are olive oil polyphenols and why are they so important for health?

Guest written by Giulia Crouch & illustration by Dóra Berczi

Polyphenols is the latest buzzword in nutrition and if you’re interested in olive oil you’ve probably heard of them.

Extra virgin olive oil (EVOO) is a rich source of unique ones – and they’re extremely healthy for us.

But what exactly are they? What do they do for us? And is there a magic number?

This guide will break it down.

Quick summary

- Polyphenols are defence chemicals found in plants 

- They protect the plant from threats like bugs, heat and UV light

- When we eat them they have a protective effect in our bodies too

- They act as antioxidants but also feed our gut microbes, protecting us against disease

- They’re thought to positively impact brain health too via the gut-brain axis 

- Extra virgin olive oil is rich in unique polyphenols

- Regular olive oil is refined and striped of its polyphenols

- Polyphenols give EVOO its distinctive bitter taste and throat-tickling pungency 

- Early harvest EVOO usually contains more polyphenols than late harvest

- EVOO must have a minimum of 250mg/kg to be considered “high-polyphenol”

- Some experts believe the minimum should be around 400mg/kg

- Polyphenols naturally decline as an EVOO ages

What are polyphenols?

Polyphenols are chemicals that naturally occur in all plants. They help to defend the plant from threats such as UV light, heat and insects.

There are around 8,000 different types found across plant foods. The richest sources tend to be colourful or strongly flavoured foods like berries, herbs, spices, tea, coffee, and red onion.

Which Polyphenols Are in Olive Oil?

Over 30 different types of polyphenols have been identified in EVOO but the main ones are:

- Oleocanthal

- Oleuropein and oleacein

- Hydroxytyrosol and tyrosol

- Smaller amounts of lignans and flavonoids

Why Are Olive Oil Polyphenols Good for Health?

Though making up only a small percentage of the oil (around 2%), polyphenols are believed to be a major reason EVOO is considered so beneficial for health.

Large studies have shown that regular consumption of EVOO is good for cardiovascular health and recent reviews suggest that it may be the polyphenols in the oil that are a key driver of these benefits.

They act as antioxidants, which help to protect us against disease.

“They are also well-known for their anti-inflammatory effects, mainly through suppression of pro-inflammatory markers,” says Dr Sammie Gill, which further protects against disease.

In fact oleocanthal has been shown in studies to work on a similar anti-inflammatory pathway as ibuprofen – which might explain why they can both have that tickly back-of-the-throat sensation. 

On top of this, they have also been shown to possess antimicrobial and anticancer capabilities, says Dr Gill. 

New research has also shown that polyphenols feed our good gut microbes, driving overall good health, and, it turns out, positively impacting the brain.

A study from January of this year compared extra virgin olive oil with standard olive oil and found that a higher intake of EVOO was linked to a more diverse (healthier) gut microbiome and better brain health over two years. Whereas a higher intake of regular olive oil (which doesn’t contain polyphenols) was linked to worse gut microbiome diversity and more cognitive decline.

This is thought to be due to the fact that the gut and brain communicate with each other via the gut-brain axis.

What Counts as High-Polyphenol Olive Oil?

Polyphenol levels in EVOO can vary based on the olive variety, the time of harvest, the year and how carefully the olives are processed and how old the oil is, as polyphenols naturally decline over time.

They’re measured in milligrams per kilogram (mg/kg) and can range from around 50 mg/kg in mass-produced supermarket oils to 1,000 – or even 2,000 mg/kg – in some specialty oils.

To be classed as “high,” the European Food Safety Authority (EFSA) set a minimum of 250 mg/kg in 2012. This threshold is based on evidence showing that oils at this level can help protect LDL cholesterol from oxidative damage, which is linked to cardiovascular health.

However, many experts argue the benchmark should be higher, around 400 mg/kg, to maximise benefits. 

At Honest Toil, polyphenol levels always exceed this, typically sitting between 420–540 mg/kg. This is because the oil is made from Koroneiki olives, a naturally high-polyphenol variety, and because the olives are harvested early, when they are still green – which generally produces oil with higher polyphenol content.

For health benefits, EFSA suggests around 20 grams (about 1–2 tablespoons) of high-polyphenol EVOO per day. 

In practice, people in Greece, Italy, and Spain often consume more than this – around 4 tablespoons daily – naturally increasing their intake of beneficial polyphenols.

How Much Should You Have Per Day?

We’re not sure yet, says Dr Gill. “Unlike macronutrients and micronutrients, there are no established guidelines for the recommended intake of polyphenols.”

There aren’t yet studies on very high-polyphenol oils (around 1,000 mg/kg and above). Most studies only compare moderate differences.

What we do know is that 250 mg/kg is a good minimum to aim for and studies suggest that many supermarket oils don’t reach this – often around 100–150 mg/kg.

We also know it’s better to avoid polyphenol supplements and stick to getting them from EVOO.

Polyphenol supplements, containing very high amounts, may have downsides such as: “inhibiting iron absorption and digestive enzymes,” says Dr Gill.

Dr Simon Poole, an expert in the Mediterranean Diet, agrees supplements could be problematic. “There's a possibility that very high levels may result in a loss of beneficial antioxidant effects and may paradoxically shift towards harmful pro-oxidant activity, as described in this review.”

Do Polyphenols Decrease Over Time?

One important thing to remember is that polyphenol levels decline over time – particularly if the oil is exposed to light, heat and oxygen.

For this reason, it can make sense to choose an oil with a higher starting level, particularly if you don’t use it that quickly. 

To preserve polyphenols: store your EVOO a cool, dark place; keep the bottle tightly sealed and, for the most benefits, use it within a reasonable time frame after opening.