`Use Any Olive Oil You Like, "As Long as it's Green and Bitter" - Olive Oil Times
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Use Any Olive Oil You Like, "As Long as it's Green and Bitter"

By Julie Butler
May. 11, 2011 10:23 UTC

The European Food Safety Authority (EFSA) last month approved the claim that ​“con­sump­tion of olive oil polyphe­nols con­tributes to the pro­tec­tion of blood lipids from oxida­tive dam­age.”

Here we speak to the leader of the research team whose inves­ti­ga­tion of EVOO’s health ben­e­fits was piv­otal to the approval.

Dr. María-Isabel Covas is head of the Cardiovascular Risk and Nutrition Research Group at the IMIM-Research Institute, Hospital del Mar in Barcelona, Spain. She is also head inves­ti­ga­tor of the CIBER of Obesity and Nutrition (CIBEROBN) a Network of Research Groups of Excellence in Spain. Last week she won an inau­gural Catalan olive oil DOPs prize in recog­ni­tion of her out­stand­ing research.

Dr. Covas explains why lipid oxi­da­tion mat­ters and that the key to ben­e­fit­ing from EVOO is not to take it as a med­i­cine. ​“You must enjoy it.”

Please tell us about the research that led to the EFSA approval.

Our research started about twelve years ago and focuses on the health ben­e­fits of olive oil, in par­tic­u­lar the effects of its polyphe­nols on the heart. Until 2004, it had been known that olive oil was good for you but there was a con­tro­versy over the in vivo antiox­i­dant power (in humans) of the polyphe­nols.

We started sev­eral stud­ies with Catalan olive oil and our hypothe­ses were suc­cess­ful but we needed full proof, because in this area of sci­ence, for a health pro­fes­sional to be able to say, ​“take this, it is good for you,” you need evi­dence from ran­dom­ized and con­trolled stud­ies with humans. You also need to be very accu­rate when you deter­mine the aver­age daily dose nec­es­sary to get suf­fi­cient quan­ti­ties of polyphe­nols because the effect will be not a phar­ma­co­log­i­cal one but phys­i­o­log­i­cal.

We, there­fore, held an ini­tial trial with Catalan olive oil involv­ing about 30 healthy indi­vid­u­als here in Catalonia. We also did another study here with 38 peo­ple with sta­ble coro­nary heart dis­ease. Then, in order to have defin­i­tive clin­i­cal proof, we orga­nized a European study, the EUROLIVE Study, encom­pass­ing 200 healthy indi­vid­u­als from five European Countries. They con­sumed 25ml/day of three types of olive oil that were sim­i­lar but dif­fer­ent in polyphe­nol con­tent.

What were the results of these stud­ies?

We were able to prove that there was an increase in lev­els of high-den­sity lipopro­tein (HDL), the good cho­les­terol and that this was directly pro­por­tional to the olive oil polyphe­nol con­tent. There was also a proven decrease in lipid oxi­da­tion, one of the main risk fac­tors for car­dio­vas­cu­lar dis­ease, and this risk was shown to be inversely related to the polyphe­nol con­tent of the olive oil.

All this work paid off on April 8 when EFSA con­cluded that a cause and effect rela­tion­ship had been estab­lished between the con­sump­tion of olive oil polyphe­nols and pro­tec­tion of low-den­sity lipopro­tein (LDL- the ​“bad” cho­les­terol) par­ti­cles from oxida­tive dam­age and that this was a ben­e­fi­cial phys­i­o­log­i­cal effect. This was mainly based on our study and we were really happy about it.

How much EVOO must we con­sume each day to ben­e­fit from this antiox­i­dant effect?

EFSA says that 5mg of hydrox­y­ty­rosol and its deriv­a­tives (e.g. oleu­ropein com­plex and tyrosol) in olive oil should be con­sumed daily.

That means tak­ing 25ml/day of a vir­gin olive oil that con­tains 300mg/kg of polyphe­nols, or 30ml/day of a vir­gin olive oil con­tain­ing 200mg/kg of polyphe­nols. (Virgin olive oils have an aver­age con­cen­tra­tion of around 250mg/kg of phe­no­lic com­pounds.)

These amounts, if pro­vided by mod­er­ate amounts of olive oil, can eas­ily be con­sumed in the con­text of a bal­anced diet. However, the con­cen­tra­tions in some olive oils may be too low to pro­vide a suf­fi­cient amount of polyphe­nols while still main­tain­ing a bal­anced diet.

Why is it impor­tant to reduce oxida­tive dam­age to blood lipids?

We know that high cho­les­terol is dan­ger­ous, but the great­est dan­ger is when this cho­les­terol is oxi­dized because it can then read­ily pro­mote ath­er­o­scle­ro­sis (build-up of fatty deposits on artery walls). Of course, if you have high cho­les­terol you have more prob­a­bil­ity of a large amount of it being oxi­dized.

What are you research­ing now?

There are two main areas in which we are con­tin­u­ing our work on olive oil. One is to assess if besides pro­mot­ing an increase in HDL cho­les­terol, the polyphe­nols in olive oil also increase the func­tion­al­ity of this lipopro­tein. That’s because the impor­tant thing is not only to increase the lipopro­tein (HDL) but that this pro­tein be func­tional. So one thing is mea­sur­ing the quan­tity and another is mea­sur­ing the func­tion­al­ity.

Why it is ben­e­fi­cial to increase the func­tion­al­ity of HDL?

The inverse rela­tion­ship between HDL cho­les­terol lev­els and coro­nary heart dis­ease has stim­u­lated inter­est in phar­ma­co­log­i­cal agents that ele­vate plasma HDL. However, recently there has been an unex­pected asso­ci­a­tion of a drug that increases plasma HDL‑C with increased car­dio­vas­cu­lar mor­tal­ity. One of the con­se­quences of this is the con­sid­er­a­tion of whether the func­tional qual­ity of HDL is per­haps more impor­tant than how much of it is cir­cu­lat­ing in the blood.

What is the other area of your cur­rent research?

We are work­ing to increase our knowl­edge of the mech­a­nism by which the polyphe­nols in olive oil exert their ben­e­fi­cial effects. Besides the clas­sic role of scav­eng­ing free rad­i­cals, we think — and have some sup­port­ing data – that EVOO has a nutrige­nomic effect. In other words, we are inves­ti­gat­ing the pro­tec­tive fac­tor that EVOO’s high polyphe­nol con­tent pro­vides in terms of the expres­sion of genes related to ath­er­o­scle­ro­sis.

Is it okay to fry with olive oil?

Yes, because although lipid per­ox­ides – which increase the risk of ath­er­o­scle­ro­sis, can­cer, and other chronic degen­er­a­tive dis­eases – are formed when olive oil is heated, the polyphe­nols in it pro­tect against this lipid per­ox­i­da­tion.

However, fry­ing once with EVOO reduces the polyphe­nols by half and the sec­ond time they are reduced to about 18 – 20% of the orig­i­nal. So it is not advis­able to cook with EVOO more than once, or twice at max­i­mum.

How should we use EVOO in order to max­i­mize its health ben­e­fits?

You need to use EVOO as your main fat, for cook­ing and other pur­poses. It’s not advis­able to have huge quan­ti­ties, because it is fat, but sim­ply to use EVOO as both your raw fat and for cook­ing. And to com­bine it with a healthy diet, that means with a lot of veg­eta­bles.

Another thing many peo­ple don’t know is that olive oil must be kept in a cool, dark place, and ide­ally, it should be used within a year of the pro­duc­tion date. Some bot­tles are clear and that’s wrong. But most EVOO now comes in dark bot­tles.

Also, peo­ple in Mediterranean coun­tries tend to know that EVOO is greener and more bit­ter but some­times peo­ple in other coun­tries don’t like it to be so bit­ter. So I say that every­one must find an olive oil that they like. You need to taste sev­eral types and get the one you like the most, as long as it is green and bit­ter. You want it to be bit­ter because it’s the con­cen­tra­tion of polyphe­nols that con­tribute to that taste.

You don’t need to take olive oil as med­i­cine, you must enjoy it. I think it is a very impor­tant part of the health ben­e­fits, to enjoy it.

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