Cooking in extra-virgin olive oil adds and boosts antioxidant power 07/11/2019
Traditional Mediterranean diets are typically rich in olive oil, and have been linked to better cardiovascular health.
And clinical studies have convincingly confirmed that olive oil’s cardiovascular benefits flow from the potent, tyrosol-type antioxidants found only in extra-virgin olive oil or EVOO.
For example, see Olive Oil Benefits Linked to EV Grade's Key Antioxidant. Extra Virgin Olive Oil Confirmed as Best Cardiac Prevention Choice, and related articles in the Fats & Oils section of our newsletter archive.
Several recent studies compared the effects of cooking vegetables with water versus various oils, including EVOO — and they all found that cooking veggies in EVOO raised veggies’ antioxidant power and improved people’s blood markers for cardiovascular and metabolic health: see When is Oil Better than Water?.
Now, researchers from several Spanish institutions report findings that confirm and expand on those prior discoveries, making EVOO look even better.
Cooking in EVOO boosts veggies’ antioxidant power
The new study was led by Prof. Rosa M. Lamuela of the University of Barcelona and included scientists from there and from two multi-institution centers in Spain that perform research on cardiovascular and metabolic diseases.
It was designed to explore why population studies strongly link the Mediterranean diet — characterized by high intakes of vegetables, fruits, legumes (beans and lentils), and EVOO — to better cardiovascular and metabolic health.
That link has been found in many population studies and were reliably confirmed by the large PREDIMED clinical trial, which involved more than 7,000 people. (Dr. Lamuela was among the many co-authors of that clinical trial.)
However, the apparent benefits of the Mediterranean diet haven't always manifested to the same extent in non-Mediterranean populations and the researchers behind the new study suspected that this might be due differences in cooking methods.
Accordingly, the Spanish researchers set out to see whether the Mediterranean diet’s health benefits might depend in part on the way vegetables are cooked (Rinaldi de Alvarenga JF et al. 2019).
The Spanish study was designed to measure the effects of using extra virgin olive oil on the antioxidant characteristics and capacity (power) of tomatoes, onion and garlic. They chose those vegetables because they are commonly consumed in countries closely associated with the Mediterranean diet, such as Spain, Italy, and Greece.
People in those Mediterranean countries commonly cook tomatoes, onion, and garlic in EVOO to create a saucy mix known as sofrito, which typically contains 40 different antioxidant compounds belonging to the phenol family, and a somewhat smaller variety of antioxidants belonging to the carotenoid family.
Prior studies have linked frequent consumption of sofrito-type vegetable combinations coooked in EVOO to human “biomarkers” for reduced cardiovascular risk and improved insulin sensitivity.
A key finding of the study was that cooking vegetables with EVOO causes some of the antioxidants in the vegetables to transfer to the oil, which enhances their absorption and “bioactivity”.
In other words, cooking vegetables in EVOO substantially enhances absorption of their antioxidants and boosts their health benefits in the body.
Study uncovers a new EVOO benefit
The study also revealed a previously unknown benefit of cooking veggies with EVOO.
The researchers found that cooking vegetables in EVOO yields different forms (isomers) of their antioxidant phenol and carotenoid compounds — ones that are more bio-available and exert stronger antioxidant effects.
This finding could explain why a separate study from the same research group found that making tomato sauce with EVOO enhances its anti-inflammatory effects (Hurtado-Barroso S et al. 2019).
For more on that subject, see Olive Oil Antioxidants Douse Inflammation Genes.
Fats and heart health: monounsaturated, polyunsaturated, saturated
For decades, the apparent cardiovascular benefits of olive oil were attributed to the fact that it’s unusually rich in monounsaturated fat (oleic acid).
But as we noted above, it's now clear that olive oil’s benefits flow from the potent antioxidants found only in extra-virgin olive oil or EVOO.
Most commonly used vegetable oils — except canola oil and so-called “high-oleic” sunflower oil — are very high in polyunsaturated omega-6 fats and low in monounsaturated fats.
Unlike saturated or monounsaturated fat, there’s ample evidence that polyunsaturated fats bring cardiovascular benefits.
However, there’s sharp scientific disagreement about the best intake levels of and balance between omega-6 and omega-3 polyunsaturated fats: see our Omega-3/6 Balance page and the Omega-3/6 Balance section of our news archive.)
It’s also important to note that the heart risks of diets high in saturated fat have been grossly exaggerated: see Major Study Exonerates Saturated Fat.
Further, the various types of saturated fat vary significantly in terms of their effects on cardiovascular risk factors.
However, most of the recent evidence reviews still link diets unusually high in saturated fats — typically from red meats and whole dairy foods — to a somewhat higher risk for cardiovascular disease and dementia.
If you eat lots of red meat and/or whole dairy, the available evidence suggests that you should replace some (not all) of those choices with seafood — see Low Fish-to-Meat Ratio Linked to Big Health Risks — non-starchy vegetables, beans, and whole-grains.
- Briggs MA, Petersen KS, Kris-Etherton PM.Saturated Fatty Acids and Cardiovascular Disease: Replacements for Saturated Fat to Reduce Cardiovascular Risk. Healthcare (Basel). 2017 Jun 21;5(2). pii: E29. doi: 10.3390/healthcare5020029. Review
- Hurtado-Barroso S, Martínez-Huélamo M, Rinaldi de Alvarenga JF, Quifer-Rada P, Vallverdú-Queralt A, Pérez-Fernández S, Lamuela-Raventós RM. Acute Effect of a Single Dose of Tomato Sofrito on Plasmatic Inflammatory Biomarkers in Healthy Men. Nutrients. 2019 Apr 15;11(4). pii: E851. doi: 10.3390/nu11040851.
- Hurtado-Barroso S, Quifer-Rada P, Rinaldi de Alvarenga JF, Pérez-Fernández S, Tresserra-Rimbau A, Lamuela-Raventos RM. Changing to a Low-Polyphenol Diet Alters Vascular Biomarkers in Healthy Men after Only Two Weeks. Nutrients. 2018 Nov 14;10(11). pii: E1766. doi: 10.3390/nu10111766.
- Nettleton JA, Brouwer IA, Geleijnse JM, Hornstra G. Saturated Fat Consumption and Risk of Coronary Heart Disease and Ischemic Stroke: A Science Update. Ann Nutr Metab. 2017;70(1):26-33. doi: 10.1159/000455681. Epub 2017 Jan 27.
- Rinaldi de Alvarenga JF, Quifer-Rada P, Francetto Juliano F, Hurtado-Barroso S, Illan M, Torrado-Prat X, Lamuela-Raventós RM. Using Extra Virgin Olive Oil to Cook Vegetables Enhances Polyphenol and Carotenoid Extractability: A Study Applying the sofrito Technique. Molecules. 2019 Apr 19;24(8). pii: E1555. doi: 10.3390/molecules24081555.
- Rinaldi de Alvarenga JF, Tran C, Hurtado-Barroso S, Martinez-Huélamo M, Illan M, Lamuela-Raventos RM. Home cooking and ingredient synergism improve lycopene isomer production in Sofrito. Food Res Int. 2017 Sep;99(Pt 2):851-861. doi: 10.1016/j.foodres.2017.01.009. Epub 2017 Jan 11.
- Rodriguez-Rodriguez R, Jiménez-Altayó F, Alsina L, Onetti Y, Rinaldi de Alvarenga JF, Claro C, Ogalla E, Casals N, Lamuela-Raventos RM. Mediterranean tomato-based sofrito protects against vascular alterations in obese Zucker rats by preserving NO bioavailability. Mol Nutr Food Res. 2017 Sep;61(9). doi: 10.1002/mnfr.201601010. Epub 2017 Apr 5.
- Vallverdú-Queralt A, Regueiro J, Rinaldi de Alvarenga JF, Torrado X, Lamuela-Raventos RM. Home Cooking and Phenolics: Effect of Thermal Treatment and Addition of Extra Virgin Olive Oil on the Phenolic Profile of Tomato Sauces. J Agric Food Chem. 2014 Apr 9;62(14):3314-3320. doi: 10.1021/jf500416n. Epub 2014 Mar 27.