Olive Oil Polyphenols - what's it all about

HIGH POLYPHENOL OLIVE OIL – BITTER IS BETTER (within limits!)

For an olive oil to call itself ‘extra virgin’, it must, by definition, be cold pressed, fresh, free from defects in taste or aroma (organoleptic properties), and must fulfil certain chemical criteria (acidity, peroxide levels). But even within this band of ‘extra virgin’ olive oils, the range in these qualities is vast, and to date two other important attributes - provenance and health value - have remained relatively ignored.  These differences can be very difficult to detect from current commercial labelling. In other words,  not all ‘EXTRA VIRGIN’ Olive Oils are equal, so it helps to know what to look for.

One of the qualities I am most interested in, as a doctor and producer of my own olive oil, is how healthy the olive oil is – and how should its health value be measured? Health claims on food products can be very misleading, and for this reasons the EU commission (Regulation (EU) No. 432/2012 May 16, 2012 ) has defined a list of permitted health claims for various foods – including olive oil.

The permitted health claims for olive oil relate to olive oil polyphenols, oleic acid (a specific healthy type of monounsaturated fatty acid), vitamin E and other monounsaturated and/or polyunsaturated fatty acids (for full list see here).  In this blog I focus on olive oil Polyphenols.

WHAT ARE POLYPHENOLS AND WHY ARE THEY GOOD FOR YOU?

During normal daily life, the body produces numerous harmful products, rather like the exhaust fumes from a car! Many of these harmful products are known as ‘reactive oxygen species’ which cause damage to cell membranes, and potentially carcinogenic compounds which cause damage to the genetic code of cells. The amounts of these compounds in the body are increased by unhealthy lifestyles such as smoking, pollution, stress – and poor diet.

Fortunately, the body has an armoury of  ‘good’ chemicals – antioxidants - which help to ‘mop up’ these harmful substances. These include certain vitamins C, E, K, D, certain minerals - and yes you guessed it -  POLYPHENOLS!  Importantly, all of these antioxidants come from our diet. Polyphenols are one of nature’s natural ‘antioxidants’ found in a range of plant foods, and one of the richest sources is high quality olive oils.  

Many people know that the Mediterranean diet is healthy – and one of the main reasons for this is the high intake of good quality olive oil. Of course Olive oil contains many other healthy substances such as monounsaturated fatty acids, (oleic acid), vitamins E and K - but it also contains more than 30 different types of POLYPHENOLS.

Scientific research has shown that long-term dietary intake of Polyphenols is good for health and the high concentration of polyphenols in olive oil may be one reason why the Mediterranean diet is so helpful. It has been shown that polyphenols are associated with a lower risks of cardiovascular disease (heart disease, stroke, high blood pressure, thrombosis), type II diabetes, neurodegenerative diseases (eg Alzheimer’s disease, Parkinson’s disease), osteoporosis, gut disorders, lung damage,  inflammatory disorders, cancers (especially colon, breast and skin cancer) and obesity.  Polyphenols also have antimicrobial and antiviral activity (this article summarises much of this research)

As mentioned above, these health effects of polyphenols are LARGELY related to their antioxidant and ‘free radical scavenging’ properties and their anti-inflammatory effects. But another helpful aspect, separate from their antioxidant role, is that Polyphenols promote a healthy ‘microbiome’ - gut bacteria -  (68, 69) which in turn may contribute to the beneficial effects of polyphenols on chronic diseases risk, such as improved insulin sensitivity and the atheroprotective and hepatoprotective effects of polyphenols (73–77).

The most important olive oil polyphenols are: oleocanthal, oleacein, oleuropein, hydroxytyrosol, and tyrosol, and also verbascoside, luteolin-7-O-glucoside, rutin, quercetin, luteolin. Oleocanthal – with its pungent peppery taste is as potent an anti-inflamatory agent as Ibuprofen (both are COX-2 inhibitors). A daily consumption of 50 g of extra virgin olive oil, which contains around 10 g oleocanthal, is comparable to 10% of the low/daily dosage of ibuprofen for treatment of pain. Moreover, regular consumption of oleocanthal may protect against cardiovascular and some types of cancer and progressive brain disorders such as Alzheimer’s disease. Oleocanthal is responsible for the pungent peppery quality of olive oil (file:///C:/Users/stavi/Downloads/processes-09-00953-v2.pdf)

Oleacein has anti-inflammatory, antioxidant and anti-thrombotic properties and contributes to the bitterness of olive oil. Oleacein generally has lower storage stability and heat stability compared to oleocanthal. Oleuropein, hydroxytyrosol, and tyrosol are the most potent of the antioxidants and contribute to the bitterness of olive oil. 

WHAT DETERMINES THE POLYPHENOL LEVELS IN OLIVE OIL AND HOW MUCH SHOULD YOU CONSUME?

Olive Oil Polyphenol levels depend on many factors, notably olive variety, harvest time, transit time between harvest and pressing, and extraction and storage procedures [polyphenol levels,30,31,32,33

Olive variety and polyphenol levels: There are more than 100 different olive varieties, and their polyphenol content can range from 50-1000mg/kg.

• For the highest polyphenol levels, look for olive oils made from Koroneiki, Coratina, Conicabra, Moraiolo and Picual varieties.

Harvest time : the best time to pick olives for high quality and healthy olive oil is just as the olives are turning from green to black (i.e. red), so that there is a good mix of green, red and black olives. The reason for this is because less ripe olives have higher levels of the polyphenols oleuropein, luteolin-7-O-glucoside (total antioxidant capacity) and of α-tocopherol (vitamin E); and a lower ratio of linoleic acid/linolenic acid (ω-6/ω-3) than more ripe olives; on the other hand, as the olives ripen and become darker, levels of  hydroxytyrosol (another important polyphenol) and linoleic acid (omega 6) increase, and the oil becomes more aromatic ‘fruity’ and palatable. As olives ripen/mature, the ω-6/ω-3 ratio increases largely due to increases in linoleic acid levels (omega 6). Oleuropein is highest in green unripe olives, and progressively decreases as the fruit ripens. Hydroxytyrosol and tyrosol are derivatives of oleuropin, and are also potent antioxidants; their levels generally increase with olive maturation; flavonol glycosides, such as quercetin 3-rutinoside (rutin) and luteolin 7-glucoside do not change so much with stage of maturity

• In practical terms, look for an early harvest (November) olive oil as this results in oil rich in antioxidants, low omega 6:3 levels, high quality, high stability during storage and long shelf-life.

How the olives are harvested and processed:

Olives should be picked with as little damage to the fruit (and tree) as possible; hand picking is best, and the olives should be collected into containers with large breathing holes, to enable air circulation; the olives should be pressed ideally within 4 hours of picking, but certainly on the same day; the longer olives are left sitting before pressing, the greater the degree of oxidation, and the lower the quality of olive oil.

The main processing steps involved in olive oil production consist of cleaning of harvested olives, crushing, malaxing, and phase separating. Modern methods use a continuous centrifugation system [25,39] with either a two-phase or a three-phase decantation [25,40,41]. The system commonly employs metal crushers for the malaxation step, which increases extractability of the oil and recovery of total phenolics [25]. Two-phase decanters in place of a three-phase centrifugation reduces the use of water addition to maxalated olive paste means higher levels of polyphenols in the extracted oil.

Filtered or unfiltered olive oil? – A significant loss of polyphenols (notably the water soluble ones) occurs when olive oil is filtered; however, an unfiltered oil will appear cloudy due to the retained fragments of fruit; this can add to its taste and aroma, and many people prefer this taste; others however prefer the clean filtered look; but it is a matter of taste.

• Look for a hand-harvested olives, which are pressed the same day as picking, a two phase decanter, and unfiltered. If polyphenols are the key issue, then go for unfiltered or ‘racked’ olive oil.

How much should we eat

Most people consume around 0.1 to 1.0 g of polyphenols per day [10] with the main dietary source being fruits, vegetables, herbs, spices, seasonings, coffee, tea, or wine – and, in the Mediterranean regions, olive oil. However, given that Italians consume more than 5 times the amount of olive oil than other nations, and that Greeks consume more than twice as much as Italians, it is likely that the polyphenol consumption by Greeks and Italians is considerably higher!

But exactly how much the daily polyphenol intake needs to be in order to have full health benefits is not yet clear. Most of the research looking at the benefits of olive oil polyphenols has been done in  the laboratory setting, but also by looking at epidemiological studies.  In order to verify their beneficial impact on human health, more in vivo studies and well-designed clinical trials are still necessary. Nonetheless, the preliminary results seem to be pretty encouraging in terms of prevention and treatment of cancer or cardiovascular and neurodegenerative diseases.

An increase in consumption of virgin olive oil and other plant products rich in polyphenolic compounds, specifically in populations with low olive oil intake, does seem to be rational and provide diverse health benefits.

However, this does not mean that everyone should start eating vast quantities of concentrated polyphenols. First because it seems to be the e that the full benefits of polyphenols arise when consumed as part of a well varied diet;  ‘supplements’ of polyphenols – may actually do more harm than good[i]. Second, there is some evidence that too many polyphenols may be bad for you (Health problems have been documented from polyphenolic botanical extracts in beverages, especially for individuals with degenerative disease, high blood pressure, thyroid disease, epilepsy, or heart disease (polyphenolic extracts). Dietary polyphenols can also reduce the absorption of some vitamins such as thiamin and folic acid, (vitamin absorption) and iron (iron chelation). What’s more,  the benefits of polyphenols may be organ specific.

So how much is a good amount? 

Most olive oils contain between 50-1000mg/kg olive oil, and the EU regulations state that an oil with a polyphenol level of 250mg/kg or above can qualify as ‘healthy’. So my advice is to aim for an olive oil with a range of 400-800 mg/kg. You will generally find that olive oils in this range also have low acidity (less than 0.5%) and low peroxide levels.

The EFSA health claim regarding polyphenols of virgin olive oil, when reported on labels, can be a useful legislative tool allowing the consumer to recognize the highest quality segment within the product category of extra virgin olive oils. However, to date, only a very low percentage of producers apply this claim on the label, partly because of ignorance amongst producers, but also because of lack of suitable analytical methods tin remoter regions.

Our “Hygeia” and “Cretan Liquid Gold Organic” Extra Virgin Olive Oils belong to this special category of olive oils known as “High Polyphenols Olive Oil”, “Medical Grade Olive Oil” or “Health Claim Olive Oil”, recognised by the European Food Safety Authority ( EFSA - Olive Oil Health Claim EU 432/2012 ). 

Our olive oils range between 400-600mg/kg, which we believe is just right for achieving a balance between good health with good taste. 

[i] Some manufacturers recommend intakes over 100-times higher than those currently associated with a Western diet and the effects of this is simply unknown: Supplementation trials of antioxidants have been associated with adverse effects, including increased mortality or stroke in some studies