Published on May 27, 2015

Olive Oil: Liquid Gold with Shades of Black & White

By Genesis Dietitian Teresa Pangan

Olive OilFats in the diet are highly controversial.

You’ll see people arguing about animal fats, seed oils and almost everything in between.

But one of the few fats that most people agree is healthy is extra virgin olive oil.

This oil, part of the Mediterranean diet, is a traditional fat that has been a dietary staple for some of the world’s healthiest populations. There is actually quite a bit of research behind the health effects of olive oil.

What is olive oil?

Olive oil is mainly comprised of monounsaturated fatty acids or often called MUFAs. This is an unsaturated type of fat rather than the type you hear to stay away from called saturated fat. It is pressed from olives, the fruits of the olive tree.

High quality extra virgin olive oil, in particular, provides a high content of antioxidants, like polyphenols, vitamins E & K, chlorophyll and carotenoids. These are key components of olive oil if health is a priority.

There is one major problem with olive oil: it isn’t always what you think it is. Some lower quality versions can be extracted using chemicals, or even diluted with other cheaper oils. And most of the olive oils in the grocery store fit into these lesser quality versions. Therefore, buying the right type of olive oil is incredibly important. Read on to get the details.

Olive Oil Types

Extra virgin olive oil (EVOO) is the preferred version for health and taste when selecting an olive oil. EVOO means it has been produced by a simple pressing of the olives. Other grades labeled as “olive oil” without the “extra virgin” are usually produced using chemicals and other processes to extract the oil from the olives. Second, extra virgin must meet certain laboratory test criteria like levels of acidity and peroxide. Finally, extra virgin olive oil must taste like olives and it can’t have any negative tastes that professionals refer to as “defects.”

Olive oil also can be "filtered"—or not. Unfiltered oils have tiny particles of olive flesh in them, which reduces shelf life, and may appear cloudy if those particles haven’t settled at the bottom of the bottle. Filtered is a process to take out these particles. Nutritionally unfiltered is slightly healthier but not by a lot. Also, unfiltered olive oil cannot be heated. It is best for salad dressing and drizzling.

In general, I don’t recommend looking for unfiltered as the shelf life is key (only good for 3 months) and it is very difficult to find. If you are traveling to Greece, Spain or Italy in the fall (their harvest time) and want to buy unfiltered at a vineyard that is ideal. In other cases I recommend going with the more common unfiltered.

The Good Stuff

The health benefits of olive oil come mostly from the presence of the polyphenolic compounds, which is not technically the oil part, but a non-caloric super healthy part of olive oil. Don’t get scared with some new words you have not heard of. These are all natural parts of olive oil.

Polyphenols decrease heart disease risk factors by lowering blood pressure and cholesterol, reduce blood clotting and improve the health of artery linings. In addition, there is strong evidence of the antimicrobic effect of the phenols from olive oil that successfully destroy colonies of microorganisms which may cause respiratory tract, intestinal, and genital tract infections.

Oleocanthal—a phenolic compound in olive oil that gives it a peppery, burning sensation in the back of the throat, has some preliminary research indicating it may be a preventative for Alzheimer’s. Also, oleocanthal may attack the waste center (lysosome) of cancer cells which leads to the unwanted cells’ death. Research is too early to be sure of these benefits, but it is promising.

Heat and Protection of Phenols

All vegetable oils are susceptible to heat damage—much more so than the whole foods from which they were pressed or extracted. But in the case of extra virgin olive oil, the susceptibility is significant when we want to preserve the super healthy polyphenols.

In all studies, heat exposure destroys key polyphenolic components of extra virgin olive oil. At temperatures close to 350˚F (177˚C), for example, about 60 percent of the health component dihydroxyphenol (a polyphenol compound) in extra virgin olive oil is lost after ten minutes!

Hydroxytyrosol is another extra virgin olive oil polyphenolic compound that gets damaged very quickly by heat, including heat as low as 320˚F (160˚C) according to published research studies. Alongside of this polyphenolic loss that occurs with heat exposure is also the loss of vitamin E.

Until I see studies indicating otherwise, I will play it safe with regard to heating extra virgin olive oil. These extra virgin olive oil polyphenols are simply too important to risk potential damage through heating too high. The 200-250˚F (93-121˚C) temperature range is the one I feel safest with when it comes to the heating of extra virgin olive oil and protection of its healthy polyphenols.

So from a practical perspective, if you need to cook at high heat on the stove or oven, I would use a less expensive olive oil or a cooking oil like canola.

Quest for Truly Healthy Olive Oil

Here's the catch: unfortunately, it turns out that more than half of the extra-virgin olive oil imported into the U.S. after testing did not pass the testing for true EVOO. A big part of these substandard olive oils that are being imported to the U.S. are from Italy where there is a large number of big blending operations owned by big name companies. I mean no ill to Italy, but this unfortunately is occurring.

The truth being uncovered is oils like hazelnut, corn, grape seed, and sunflower seed are being added to EVOO and then bottled and labeled as olive oil from Italy. Also, older or non-first pressed (nonEVOO) olive oils are being mixed with true EVOO and labeled as EVOO. Both these practices are fraudulent. Unfortunately, the industry right now is not policing this practice consistently. So most of the EVOO on the grocery store shelves marketed as coming from Italy is not what you and I think it is.

A study from the University of California, Davis, found that 69 percent of imports tested failed to meet a U.S. Department of Agriculture quality standard.

The main problem I have with this resulting lower-grade oil is it will not give you the health benefits that a true EVOO should give you. Even if it's not noticeably rancid, many of the heart-healthy and cancer-fighting compounds have degraded and fizzled.

Buying True EVOO

What can you do to be assured you are buying true EVOO? There are some guidelines you can follow if you are serious like me about getting the super-healthy, polyphenolic compounds you find the in highest concentrations in EVOO you buy:

Step 1: Check the Type of Bottle

First, the olive oil should be housed in dark, colored glass that protects the oil from ultra-violet light. If the bottle is clear glass or plastic, chances are good that you're looking at a poor-quality, adulterated oil.

Step 2: Check the Harvest Date

Quality oil will have a harvest date. If there is none, you likely have a variety of oils of varying grades. In general I can only find a harvest date on about 1 in 20 bottles in the grocery store. Check yourself the next time you make a trip.

You want to buy olive oil with this year’s or within last year’s harvest date. You more often find best by or expiration dates or sell by, these are not the same as a harvest date.

Ideally you want to consume olive oil within 18 months of the harvest date. It is still good up to two years after, but that is more for rancidity than health reasons.

Even if it has a harvest date, you still won't know whether an olive oil has been harvested and handled to maximize polyphenol content. Don’t despair; there are some things you can do to be diligent to get the most health out of your olive oil.

Step 3: Check the Label

Ideally you want the grower’s name and the specific location where the olives were grown. Not just the country, but also the cultivar or type of olive used to make the oil.

Step 4: Try California or Australian Olive Oil

The California and Australian Olive Oil Council has stricter criteria for their olive oils than the International Olive Oil Council (IOOC) and North American Olive Oil Association (NAOOA). Hopefully this will change in coming years.

To earn the seal, the olive oil must pass various chemical analysis standards and be taste tasted by the California Olive Oil Council’s highly trained taste panel each harvest season. You can look online to see if the olive oil you are using passed the testing. Just Google “COOC seal certified oils olive oil” and look for a list for that year.

The olive oil I am using here called California Olive Ranch did pass on 2014 and 2015 certification for the seal. I checked online. They are the biggest grocery store suppliers in the U.S. You don’t have to buy this brand; instead, learn to read the label.

Olive Oil

Bottom-Line:

I make sure most of the EVOO I buy at the grocery store has a harvest date within the last 18 months. If I have a special dish or want to take the health one step higher, I will go to a specialty food shop where the owner is familiar with the olive farm where the olives were harvested and the oil processed and purchase EVOO there. That will typically raise your price by 3 to 4 times.

The best scenario is if I can find out the olive variety that was used in the olive oil. This is similar to knowing the grape variety in wines. There are certain olives that have been tested to have high polyphenolic content (the uber healthy part of olive oil). See the chart below for names.

I use the expensive EVOO for drizzling on salads and low heat sautéing or baking. For high heat cooking I use canola oil. I even adjust recipes to a lower heat and use olive oil if I can. Another secret is to reduce the amount of oil during cooking and add just before serving a drizzle of very good EVOO for a burst of flavor and health. Also, don’t forget olive oil is not for heating in wonderful dishes like pesto, brushetta, and salad dressing. These are great ways to easily get nutrition and flavor with olive oil.

Olive Varieties by Amount of Polyphenolic Chart

Very High: Coratina, Conicabra, Koroneiki, Moraiolo, Picual
High: Bosana, Chemlali, Manzanillo, Picholine
Medium: Arbosana, Barnea, Empeltre, Frantoio, Hojiblanca, Leccino,
Low: Arbequina, Picudo, Taggiasca

Source: International Olive Oil Council

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