New results show that top grade oil beats lesser “Virgin” and “Pure” grades for enhancing cholesterol profiles and protecting blood fats
by Craig Weatherby
The list of heart benefits attributed to “extra virgin” grade olive oil grew longer in 2005, and new findings published earlier this month should make its heart-health reputation even stronger.
Olive oil heart benefits get upgraded from “mono” to stereo
For decades, researchers assumed that the exceptionally high proportion of monounsaturated fatty acids in olive oil explained why olive-loving countries like Greece, Italy, Spain, and Portugal enjoy reduced rates of heart disease.
This perfectly reasonable hypothesis stemmed from tests showing that oleic acid—the monounsaturated fatty acid in olive oil—exerts beneficial effects on people's blood cholesterol profiles.
(Oleic acid is abundant only in olive oil, macadamia nut oil, and special “hi-oleic” safflower and sunflower oils. It also occurs naturally in our unrefined sockeye salmon oil supplement.)
But the results of American and Spanish studies published last year added a second source of cardiovascular benefits. These discoveries upgraded our perspective on extra virgin olive oil's cardiovascular benefits from the older “mono”-based hypothesis to a new “stereo” scenario.
The new, second source of olive oil cardiac benefits is the extraordinarily potent tyrosol antioxidants abundant in extra virgin grade oil, and, to a lesser extent, in virgin grade olive oil.
Here's what we reported last January (see “Extra Virgin Olive Oil Seen Superior for Reducing Cardiac and Cancer Risks”):
- “…last September , American scientists isolated a previously unknown phenol in olive oil called oleocanthal, which exerts anti-inflammatory effects similar to those that non-steroidal anti-inflammatory drugs or NSAIDS (e.g., Advil, aspirin) exert on the body's inflammatory COX enzymes.… Because the preventive benefits that aspirin and other NSAIDs bring heart patients relate to these drugs' anti-inflammatory, COX-inhibiting effects, it makes sense that the anti-inflammatory [COX-inhibiting] phenols in olive oil would bring similar cardiac benefits.”
- “Spanish researchers who were conducting a study on blood vessel function in human volunteers last year  found that an olive oil rich in antioxidant polyphenols—that is, an unrefined, extra virgin grade oil—produced a significant improvement.… In contrast to the extra virgin oil, the antioxidant-poor oil—one like the cheap, refined, ‘pure' grade oils that dominate the mass market—had very little beneficial effect.”
Now, new findings from Spain support and expand the heart-health promise of the antioxidant polyphenols in extra virgin olive oil, suggesting that they provide some of the cholesterol-lowering effects once attributed solely to the monounsaturated fatty acid (oleic acid) that's equally abundant in all grades of olive oil.
Eurolive study findings affirm unique heart benefits of extra virgin olive oil
Dr. Maria-Isabel Covas led a team at the Municipal Institute for Medical Research in Barcelona determined to examine the effects of olive oil phenols on three key risk factors in disease:
1) blood levels of triglycerides, 2) blood levels of cholesterol, and 3) damage to blood lipids and arterial tissues from free oxygen radicals (so-called “oxidative stress”).
They started with a small pilot study that showed positive results (Covas MI, de la Torre K, et al 2006), and went on to test them in a much larger “Eurolive” study (Covas MI, Nyyssonen K, et al 2006).
The positive findings from the Eurolive trial hold significance because the study was so large and well-designed.
The Spanish researchers recruited 549 healthy men from five European countries (Spain, Denmark, Finland, Italy and Germany).
They divided the volunteers into three groups, each of which was instructed to replace their normal cooking oils (e.g., canola, soy, corn) and condiment fats (e.g., butter, margarine) with just under one ounce per day (25 mL) per day of one of three olive oils.
Each group's olive oil contained a different level of phenolic antioxidants, measured as milligrams per kilogram (mg/kg):
- Low phenol level (2.7 mg/kg, as in a cheap, refined “pure” grade oil)
- Medium phenol level (164 mg/kg, as in a “virgin” grade oil)
- High phenol level (366 mg/kg, as in an “extra virgin” grade oil)
After the first three weeks, each group switched to one of the other oils for another three weeks. (To eliminate any possible effects from prior consumption of olive oil, each of the two oil-consuming periods in this “crossover” trial was preceded by two weeks of abstinence from olive oil.)
The researchers checked adherence with the regimen by testing the participants' urine for signs of the main phenols in olive oil (tyrosol and hydroxytyrosol), and found compliance good across the board.
In the end, the results were clear, with two out of three of the observed beneficial effects linked closely to the widely divergent phenol contents of the different grades of olive oil consumed by each of the three test groups:
The high-phenol (i.e., extra virgin) olive oil outperformed the other two oils (virgin and pure grade) when it came to enhancing three factors helpful to cardiovascular health:
- Healthiest cholesterol ratios (i.e., lowest total cholesterol in relation to “good” HDL cholesterol)
- Biggest rise in “good” HDL cholesterol (up by 0.045 mmol/L versus only 0.032 mmol/L for medium-phenol oil and 0.025 mmol/L in the low-phenol oil group)
- Biggest drop in levels of oxidized LDL cholesterol (down by 3.21 U/L versus only 1.48 U/L for medium-phenol oil and a rise of +1.21 U/L in the low-phenol oil group). Note: The monounsaturated oleic acid in olive oil tends to reduce LDL oxidation, and may have been partly responsible for this effect
All three oils reduced subjects' triglyceride levels: an outcome that suggests the monounsaturated oleic acid found at equal levels in all olive oils is largely responsible for this particular cardiovascular benefit.
As the Barcelona team concluded, “Olive oil is more than a monounsaturated fat. Its phenolic content can also provide benefits for plasma [blood] lipid [triglyceride/cholesterol] levels and oxidative damage.”
Together with the findings we reported last January, these results make it quite clear that among all the cooking options, extra virgin olive oil remains the best choice for heart health, as well as a delicious sensory delight.
- Covas MI, Nyyssonen K, Poulsen HE, Kaikkonen J, Zunft HJ, Kiesewetter H, Gaddi A, de la Torre R, Mursu J, Baumler H, Nascetti S, Salonen JT, Fito M, Virtanen J, Marrugat J, EUROLIVE Study Group. The effect of polyphenols in olive oil on heart disease risk factors: a randomized trial. Ann Intern Med. 2006 Sep 5;145(5):333-41.
- Covas MI, de la Torre K, Farre-Albaladejo M, Kaikkonen J, Fito M, Lopez-Sabater C, Pujadas-Bastardes MA, Joglar J, Weinbrenner T, Lamuela-Raventos RM, de la Torre R. Postprandial LDL phenolic content and LDL oxidation are modulated by olive oil phenolic compounds in humans. Free Radic Biol Med. 2006 Feb 15;40(4):608-16. Epub 2005 Oct 18.
- Marrugat J, Covas MI, Fito M, Schroder H, Miro-Casas E, Gimeno E, Lopez-Sabater MC, de la Torre R, Farre M; SOLOS Investigators. Effects of differing phenolic content in dietary olive oils on lipids and LDL oxidation--a randomized controlled trial. Eur J Nutr. 2004 Jun;43(3):140-7. Epub 2004 Jan 6.
- Weinbrenner T, Fito M, Farre Albaladejo M, Saez GT, Rijken P, Tormos C, Coolen S, De La Torre R, Covas MI. Bioavailability of phenolic compounds from olive oil and oxidative/antioxidant status at postprandial state in healthy humans. Drugs Exp Clin Res. 2004;30(5-6):207-12.
- Weinbrenner T, Fito M, de la Torre R, Saez GT, Rijken P, Tormos C, Coolen S, Albaladejo MF, Abanades S, Schroder H, Marrugat J, Covas MI. Olive oils high in phenolic compounds modulate oxidative/antioxidative status in men. J Nutr. 2004 Sep;134(9):2314-21.