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What is EXTRA in extra virgin olive oil? Olive oil and the Mediterranean diet

written by Marsha Seidelman, M.D.
on Wednesday, 9th October ,2013

Last week, my son told me about an NPR program regarding the Mediterranean diet and the benefits of polyphenols in extra virgin olive oil (EVOO) that he listened to on his way home from work. Within an hour, Thu emailed me to say we needed to write about this NPR story she just heard. Having missed it myself, I looked at in online. I was more fascinated by all the info on EVOO than the reference to the study itself.

It turns out, the NPR program was based on a New England Journal of Medicine article published in April, 2013 about the benefits of a Mediterranean diet. You might have heard about it then, as it made the news big time. Three groups were assigned to a low fat diet, a Mediterranean diet with extra nuts and EVOO, or a Mediterranean diet with 4 tablespoons of EVOO daily (480 calories of oil!). The study was stopped early because the rate of stroke was 30% lower in the two Mediterranean groups; it was felt to be unethical to continue and have the first group stay on the ‘low fat’ diet and be at a higher risk of stroke. The study was widely criticized in the medical literature for many reasons, including: the ‘low fat’ diet was 37% fat (American Heart Association 'low fat' refers to less than 30% and by other criteria closer to 20%); early apparent benefits in the study might be due to prior conditions, such as increased rates of obesity in the 'low fat' group; and ending the study early might have exaggerated the benefits.

In any case, many of the critics believed that a Mediterranean diet is indeed beneficial, just that this study was not a good one to prove that point. To be clear, the term ‘Mediterranean diet’ is a concept, not a specific diet. In fact, it’s a relatively new nutrition plan. It developed in impoverished Greece, Italy and Spain after WWII when minimal meat was available. It emphasizes fresh fruits, vegetables, beans, nuts, seeds, unrefined grains, and olive oil and includes fish and wine, with minimal higher fat foods like meat and dairy. Personally, I use this as the basis for my own nutrition.

What I found more interesting about the NPR piece and its links was the info about olive oil and all its terminology. I’ve always known that I should pay attention to all the different olive oils, but didn’t realize that there’s a culture built around them equivalent to that of fine wines. Testers are trained about a “sensory standard” to recognize the peppery taste and record the number of coughs a sip causes.

The better oils are higher in polyphenols, which was part of the focus of the NPR piece.
Polyphenols are the antioxidants in olive oil that are good for you, but also good for the oil, improving its shelf life. Better oils with the highest levels of polyphenols taste peppery and sting the back of the throat a little, inducing a cough or two – that’s evidently a good thing! Unlike wine, EVOO is at its best the day it is produced. It can stay fresh in a dark bottle for a while, but slow degradation begins as soon as you open the bottle. It may stay fresh up to 4-6 months in a dark cool place, or, up to a year if refrigerated. It can become cloudy and too thick to pour when cold, but when it stands at room temperature again, it will resume its clear liquid form.

Olive oil varieties are graded by their level of acidity. Cold pressed is the best – a chemical-free pressure that results in a natural level of low acidity. EVOO is produced after the first cold pressing, and has the lowest acidity. Then, in order of increasing acidity are virgin, then refined. “Fino” refers to a blend of extra virgin and virgin, while plain old “olive oil” is a blend of virgin and refined. “Light” olive oil is a US marketing term and has the same number of calories and monounsaturated fats as the others, but because it is made using an extremely fine filtration process, its color and fragrance are lighter, hence the name. The milder flavor makes it better for baking and cooking when you don’t want the taste of the olive oil. It also has a higher smoke point, so it can be used for frying at a higher heat. The other olive oils are good for dressings and marinades or cooking up to a medium heat.

Most of the olive oil consumed in the US is produced in California. One of the studies I accessed via the NPR site was done at University of California, Davis. They looked at the quality of retail brands of EVOO and compared domestic with imported brands. I’m proud to say that 90% of the domestic olive oils, but only 31% of imported ones were of proper quality to match their labels. Others had less expensive components or were described as rancid or musty. The findings were confirmed by an Australian group. The best news was that Costco’s Kirkland Organic EVOO was well rated. Having bought this in the past, my only problem with it is that it’s too tall to fit on my shelf; I need to pour it into a smaller bottle that can fit. I'm also not sure that I used it within the recommended 6 months. I might need to put everyone in my family on a diet with 4 tablespoons of EVOO daily to do that!

SO – the extra in extra virgin olive oil – is that it’s extra virgin – less processed, less acidic and better for dressings, marinades and low-heat cooking. Thanks for coming on this Mediterranean journey with me!

Estruch, R., NEJM 368(14):1279-90.
Herbst and Herbst. The New Food Lover's Companion, Fifth Ed., 2013.

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