Wednesday, April 16, 2008

Olive Oil Buyer's Guide

Olive oil is one of the few good vegetable oils. It is about 10% omega-6 (n-6) fatty acids, compared to 50% for soybean oil, 52% for cottonseed oil and 54% for corn oil. Omega-6 fatty acids made up a smaller proportion of calories before modern times, due to their scarcity in animal fats. Beef suet is 2% n-6, butter is 3% and lard is 10%. Many people believe that excess n-6 fat is a contributing factor to chronic disease, due to its effect on inflammatory prostaglandins. I'm reserving my opinion on n-6 fats until I see more data, but I do think it's worth noting the association of increased vegetable oil consumption with declining health in the US.

Olive oil is also one of the few oils that require no harsh processing to extract. As a matter of fact, all you have to do is squeeze the olives and collect the oil. Other oils that can be extracted with minimal processing are red palm oil (9% n-6), hazelnut oil (10% n-6) and coconut oil (2% n-6). These are also the oils I consider to be healthy. Due to the mild processing these oils undergo, they retain their natural vitamin and antioxidant content.

You've eaten corn, so you know it's not an oily seed. Same with soybeans. So how to they get the oil out of them? They use a combination of heat and petroleum solvents. Then, they chemically bleach and deodorize the oil, and sometimes partially hydrogenate it to make it more shelf-stable. Hungry yet? This is true of all the common colorless oils, and anything labeled "vegetable oil".

Olive oil is great, but don't run out and buy it just yet! There are different grades, and it's important to know the difference between them.
The highest grade is extra-virgin olive oil, and it's the only one I recommend. It's the only grade that's not heated or chemically refined in any way. Virgin olive oil, "light" olive oil (refers to the flavor, not calories), "pure" olive oil, or simply olive oil all involve different degrees of chemical extraction and/or processing. This applies primarily to Europe. Unfortunately, the US is not part of the International Olive Oil Council (IOOC), which regulates oil quality and labeling.

The olive oil market is plagued by corruption. Much of the oil exported from Italy is
cut with cheaper oils such as colza. Most "Italian olive oil" is actually produced in North Africa and bottled in Italy, and may be of inferior quality. The USDA has refused to regulate the market so they get away with it. If you find a deal on olive oil that looks too good to be true, it probably is.

Only buy from reputable sources. Look for the IOOC seal, which guarantees purity, provenance and freshness. IOOC olive oil must contain less than 0.8% acidity. Acidity refers to the percentage of free fatty acids (as opposed to those bound in triglycerides), a measure of damage to the oil.
Fortunately, the US has a private equivalent to the IOOC, the California Olive Oil Council (COOC). The COOC seal ensures provenance, purity and freshness just like the IOOC seal. It has outdone the IOOC in requiring less than 0.5% acidity. COOC-certified oils are more expensive, but you know exactly what you're getting.

Thanks to funadium for the CC photo


lesitedanais said...

Very interesting to read, as always. I'll check my oils.
Something I always wondered, is if the goodness in the oil (or what ever fat you use actually) is destroyed by heat. I have this really nice walnut oil here but I only use it in vinaigrette, not for cooking. What do you think?

Anna said...


Great post! Of course, it sent me to the pantry looking at my olive oils! I knew there has been lots of scandal and shading dealings with EVOO from Italy, with cheaper and substandard oils blended and sold as EVOO, but it's so hard to find info that helps one choose an oil that is less likely to be compromised. And from a book called Moveable Feasts and other sources, I have been learning about how, since Roman times, much of the world's olive oil is processed, bottled and sold from Italy (hence labeled Product of Italy), but the olives are primarily grown in other countries like Spain, Turkey, and Morocco, as was the pressing in many cases (I wonder why we never seem to hear of these tankers of olive oil spilling like we do of petroleum oil). Spain, and especially Andalucia, is a major olive growing region, and is trying to get out from under Italy's oily "thumb" and promote their olive oils as their own.

As I've learned more about fats and oils the past few years, our olive oil consumption has naturally fallen as my use of home rendered lard, rendered chicken fat (schmaltz), coconut oil, butter, and ghee (clarified butter) as risen. I often prefer these fats for sautéing and browning because they are more stable in high heat and less likely to be damaged during cooking. So if a recipe says to use olive oil for any amount of time or higher heat levels, I nearly always substitute a more stable fat now (usually in a higher amount, too, especially if I'm following an Eating Well magazine recipe!).

EVOO used to be my staple oil, but not anymore. It still is my primary plant oil, though. I basically save EVOO for the salads and if I have a really special olive oil (like infused with white truffles), then I drizzle with it before serving.

The only thing I buy pure olive oil for is making my weekly mayonnaise. I find EVOO just too strong and overpowering a flavor in homemade mayo. I know that the pure OO is of lower quality, but I guess until I come up with a better option for my mayo, it's a trade-off I'm willing to make. But I'm open to suggestion, if anyone has another good option for mayo oil.

So now that I use so much less olive oil, and I know more about the corruption in the OO industry, I've stopped buying inexpensive bulk EVOO from Costco or Trader Joe's, and instead sticking to smaller bottles of oils that are unfiltered and from estates, or specifically labeled as from a region/type of olive variety, or even domestic (California grown) since I live in CA. But none of the bottles I had in my pantry (Sicilian origin of Ogghiaredda olives and California estate grown - labeled "new harvest" - of Arbequina olives) have the IOOC or COOC seal, so I'm not sure what to think about that. When restock the pantry, I'll pay closer attention to the seal issue.

I love walnut and hazelnut oils in salads! I store them in the fridge and try to use them up quickly to avoid rancidity.

lesitedanais said...

Thank you Anna for the extra information.
To come back to the original post, in France (where I come from) it says on good olive oil "premiere pression a froid" suggesting the oil was not heated. Here in the UK it does not mention anything about it. I don't know what to make of that.
Also, can someone explain what is wrong with sunflower oil? It has a bad reputation but I don't know why.

paul said...


Very useful, thanks. I have just been reading up on oils these last few days, which had left me with some specific questions. I would appreciate any help you can give! I could not find an online table listing different oils and their breakdown into MUFA, saturated, PUFA. Do you know any such resource? I notice you do not list avocado oil as healthy oil even though it is relatively low n-6 - is it because the extraction methods are bad? (seems like it should just involve squeezing, like olive oil). Finally I just read that a benefit of palm oil is vitamin E, but I also read (at wikipedia) that "Boiling it for a few minutes destroys the carotenoids and the oil becomes colourless". Since boiling is a lot lower heat than frying, does this mean that cooking at all with palm oil is a bad idea, because one is destroying nutrients? Sorry for a list of questions, and thanks for any help!


p.s. About getting good quality extra virgin olive oil, there's an online farm called McEvoy Ranch that sells oil from their their own olives. It's a little expensive, but it's also nice to know one can trust the content of the bottle!

Stephan Guyenet said...

Hi everyone, thanks for the comments. I'm at a wedding in Mexico right now, but I'll respond once I get back next week.

Stephan Guyenet said...

Hi Anais,

Basically, an oil's usefulness for cooking depends on its level of saturation. The more polyunsaturated fat it has, the less well it holds up to cooking in general. That's because polyunsaturated fat is more susceptible to oxidation so it has a lower smoke point. Saturated fat is the most stable, and monounsaturated is in between. Refining an oil increases its smoke point but can damage it, leave it with chemical contaminants and strip it of its micronutrients.

I usually say olive oil is OK for temperatures up to a light saute, but honestly I don't even use it for that. I use it in salad dressings and stews mostly, or I'll add it to a saute at the end.

Extra-virgin olive oil is the equivalent of "premiere pression a froid".

Walnut oil is mostly polyunsaturated and so should never be cooked, but it's fine for salads.

Sunflower oil varies. Regular sunflower oil is high in omega-6 polyunsaturated fat and is refined, so I don't recommend it. There is a type of sunflower oil called "high oleic" that is almost all monounsaturated however, like olive oil. It has very little omega-6 (4%). I think it's just a different variety of sunflower. If you could find unrefined high-oleic sunflower oil, it would probably be a good choice for cooking.

Even refined high-oleic sunflower oil is probably better than most other refined vegetable oils, because of its higher stability and lower omega-6 content.

Stephan Guyenet said...

Hi Paul,

My list of healthy vegetable oils was not comprehensive. I think if you can find unrefined avocado oil, it's probably a fine oil. I think most avocado oil is refined though. I would put that in the same category as refined olive oil. It has a similar amount of omega-6. Unrefined avocado oil should have a lot of color and flavor.

I get my information on the composition of different foods at Just search for the oil you're interested in and you can get a lot of information on it.

About the red palm oil, I've read that same Wikipedia entry and I don't know what they're talking about. I cook with red palm oil all the time and cooking it at the boiling temperature of water does not eliminate the red/orange color indicative of carotenoids. The vitamin E should also be stable unless you're frying the hell out of it. I have sauteed with RPO many times and it retains its color. It has a fat composition similar to butter but with a bit more omega-6.

Stephan Guyenet said...


I don't think the IOOC or COOC labels are absolutely necessary to ensure quality, but they're an easy way to be sure. If the labels aren't there, you have to go on faith. So it becomes a question of whether or not you trust the manufacturer.

Ulf said...

A little bit late to comment...

Anna, macadamia oil is an excellent oil that is very good in mayo IMO.

Marwan Daar said...

Bit late on this, but if I'm not mistaken, both olives and avocados are fruits.

Not sure if classifying them as a vegetable oil is accurate.

Marwan Daar said...

never mind, according to wiki, the term vegetable oil is simply an oil that is derived from plant sources.

By that token, coconut oil and palm oil are also vegetable oils.

Wilamo2 said...

My friend Ed said extra virgin olive oil helps with easier bowel movements and blood flow. Are both of the above true?