Searching for the Health Benefits of Extra Virgin Olive Oil - Article

By Eliza Ward

In 2013, UC Davis conducted a test of some of the more popular brands of imported “Extra Virgin” olive oils and discovered, among other things, that 69% of them did not possess the minimum characteristic needed to be called “Extra Virgin”. (For a definition of what is “Extra Virgin” and details about olive oil fraud, please see my post, “The Inconvenient Truth about Olive Oil – Part I”) The reasons why an extra virgin olive oil may not actually be “Extra Virgin” can vary, and is sometimes a result of pure ignorance or neglect. But just as likely, the reasons are more nefarious – such as intentional fraud and adulteration. But regardless of the reasons, the question remains:  Why should we care so much about our olive oil?

Polyphenols in Olive Oil and How They Work?

Polyphenols are micronutrients that are found in many of the known “superfoods” – such as olive oil, red wine, chocolate, coffee, artisan-produced fruit vinegars, and fresh and colorful vegetables.

Polyphenols in olive oil (and those other foods) can have a direct impact on our metabolic risk factors – such as high blood pressure, cholesterol and glucose – which together affect our risk of heart disease, dementia and other degenerative and chronic diseases. So, polyphenols help lower our metabolic factors, which in turn reduces the risk of heart attach and stroke, and improves our overall health. It’s the main reason the Mediterranean Diet is so touted.

Additionally, the polyphenols appear to decrease cellular proliferation and inflammation, reduce oxidation and cell damage by acting as antioxidative agents, and have anti-microbial properties – together reducing the risk of cancer and other diseases related to aging – such as osteoporosis, Alzheimer’s, arthritis, and memory loss (Hummmm…) They also helps counter the effects of bacterial and viral infections, such as HIV and HPV, and boost our immune systems.

What Factors Affect the Polyphenol Count in Olive Oil?

Time, light, heat and air are the main culprits that “kill” the positive health effects of polyphenols in olive oil – as well as decrease the stability of the prevalent lipids or fatty-acids present in olive oil, primarily Oleic Acid (or Omega-9s). As time passes, from harvest to consumption, the olive oil polyphenol count diminishes – because of the oils exposure to heat, light and air. Olive oil has a maximum shelf life of approximately two years – but often less, depending on how it was pressed, how it has been stored, and when it was bottled. Modern extraction and storage methods help extend the life of olive oils, but once that bottle is opened in your kitchen, the clock starts ticking faster.

But, there are other factors that affect the polyphenol count as well. For example:

1. Variety of olives, the weather, and where the olives are grown

Besides effecting flavor, the variety of olives grown and pressed, where they are grown, and how much water and sun they received during the growing season (how stressed the trees are) also affects the level and variety of polyphenols present in an olive oil. Desert Miracle Olive Oil, for example, has registered some of the highest polyphenol counts ever tested. They believe it’s because the olives are grown in the desert – so they get 365 days of sun, and their growing environment is well regulated and controlled, although they are not 100% sure and it varies from year to year.

2. How the olives are harvested

If olives have been roughly treated and exposed to the elements – mostly air – they will have fewer polyphenols. That’s why harvest methods and pick-to-press times are so critical. The term “Extra Virgin”, although not well understood or regulated here in the US, is supposed to mean that the olives are picked and pressed within 24 hours, and are pressed slowly to ensure little heat is generated during the oil extraction process (i.e. “Cold Pressed”). That’s also why, at, I sell only estate olive oils; the best assurance I have that the olives have been handled gently and pressed quickly is the name on the bottle. (And the best assurance that the oil has not been exposed to extreme heat in transport and storage, is to minimize the distance between the field and me.) Again, Desert Miracle’s high polyphenol count could also be attributable to the fact that it’s a modern, high-density planting which uses modern picking methods; the olives are pressed in the field within 20 minutes of picking.

3. The age of the trees

In general, the older the trees, the higher polyphenol content of the olives. You will also notice that the olive oil’s flavor gets better as the trees get older – more nicely-rounded and less harsh – indicating a more balanced collection of polyphenol compounds. Avid, long-term followers of Albert and Kim Katz, and their award-winning Katz’s Chef’s Pick Olive Oil, have probably noticed the flavor of the oil getting rounder and deeper as their trees have matured over the last 20 years. It doesn’t hurt that Albert’s groves are helped by his free-range feathered friends – Mother Nature’s way of feeding fine olives back to the trees from which they came.

4. When the olives are picked

Green olives are just un-ripe black olives, and the greener the olive when picked the higher the polyphenol count – generally speaking. The trend in the olive oil industry over the last 10 years has been towards greener and greener olive oils, picked earlier and earlier in the season. Partially because here in the US we are beginning to prefer those greener, grassier flavors. But also, early harvest olive oils are not only healthier for us, the higher polyphenol count helps preserve the oil. Where historically the French and Northern Italians (Chateau Virant, Nicolas Alziari and Opera Prima are prime examples) preferred their late-harvest oils with those buttery, ripe, olive-y flavors, the Southern Italians liked nothing better than a spicy, green and robust early harvest olive oil – the more so the farther south you go. So, if you’re craving those same strong flavors, look for brands like Olio Verde or Pianogrillo, from the region of Sicily – as far south as you can go and still, technically, be in Italy – and you will be rewarded with spice, and green and grassy flavor.

5. How and when the olives are processed

The less processing the better! Extra virgin olive oil is the first pressing of the olives (as opposed to the second or third “pressing”, which is where many low quality olive oils come from) and the olives are “pressed” carefully using mechanical methods (as opposed to a chemical extraction) in a way that maintains a low temperature throughout the extraction. True extra virgin olive oil is the highest quality olive oil, and has the highest polyphenol levels. The farther down the pressing food-chain and the more processed an olive oil is, the lower the polyphenol count – to the point where there is nothing left at all and you’re just left with a cooking fat.

The term “Extra Virgin” also signifies that the oil meets a particular flavor standard, including no off flavors, is not old, or has no musty aromas or tastes. So, when you’re buying olive oil, make sure to look for that term. But remember, “Extra Virgin” is not regulated yet in the US, so don’t buy any olive oil that’s not “Extra Virgin”, but just because it says it’s “Extra Virgin” doesn’t mean it is.

So, more to the point, look for a harvest date or lot number and always buy the most recent harvest – as freshness is paramount. That extra information also tells you someone is paying attention to what’s in the bottle, and how long the bottle has been traveling through the distribution channel or sitting on the grocery store shelf. Be aware that the term “Best-Before Date” has no meaning.  Anyone can put a best-before date on their bottle – usually about 12-18 months after it has been bottled – but it tells you nothing about the quality of the oil that went in the bottle to begin with.  Harvest date is a better indicator of quality, as estate producers almost always give you the harvest year, because they actually know what the harvest year is, because they bottled it themselves. You should also taste before you buy.

A note about harvest dates: When looking at harvest dates keep in mind that in the northern hemesphere, olives are harvested and pressed in the fall, between October and December. So, the most current year will be the prior calendar year. Only novellos are released in the same year that the olives are harvested and pressed. In other words, if it's 2018, 2017 is the most current harvest year. 

6. How the oil is stored and bottled

Any exposure of the harvested olives or the oil to heat, light or air while in transport or storage will reduce polyphenol content. One of the reasons you’ll see bottling dates (as opposed to harvest dates) on your bottle of olive oil is that many modern olive oil producers will keep their bulk olive oil in stainless steel vats and eliminate the oxygen, replacing it with nitrogen, until an order is placed. So they “bottle to order”. This helps keep the oxidative effects down and extends the life of the olive oil – and the polyphenols. But how the oil is stored also applies to how the importer and distributor and retailer are storing the oil once bottled, and how you’re storing your olive oil at home and for how long.  Keep it away from the stove, in its original bottle, in a dark and cool place, and keep the top on tight – do not decant the oil into an open container – and do not use it in any cooking application hotter than about 230 degrees, despite what one cooking celebrity likes to do with her EVOO on TV; to maintain optimum flavor and health benefits, olive oil should be used primarily in low-heat and raw applications. (For more information on high heat cooking oils, see our Rice Bran Oil product page.)

In Conclusion …

So, it’s the polyphenols in extra virgin olive oil that give it its characteristic color and unctuous flavor, as well as most of its health qualities – including the much-touted anti-inflammatory properties. But if the olive oil’s polyphenol count is low – as would be the case in this country with most olive oils labeled as “Extra Virgin”, all non-extra virgin olive oils, or any adulterated olive oils – then none of these health benefits are present – there’s just no way around it; it's what I call the "Inconvenient Truth about Extra Virgin Olive Oil".

For a selection of estate-bottled, extra-virgin olive oils available at, click here.

For information about how to select and store a quality bottle of Extra Virgin olive oil, please read “How to Select and Get the Most out of your Extra Virgin Olive Oil”.

For more information about fraudulent olive oil, please read “The Inconvenient Truth about Extra Virgin Olive Oil

(c), 2021