In a recent talk on Italian cooking, I emphasized–as I always do–the importance of good olive oil as an ingredient whose flavor is essential to many dishes. We tasted and compared the two Sicilian oils I’d brought. And then came this question from a participant: “What about cooking with olive oil? Dr. Oz says it’s toxic.”
I groaned silently and replied that, if health is the issue, an oil extracted from whole fruit seems like a better bet than a refined seed oil that has been stripped of nutrients and taste by a nasty-sounding chemical called hexane.
What comes closer to the truth–for me, at least–is that I cook almost everything in olive oil because that’s how it’s done in the Mediterranean traditions I care about. Sauteing and shallow frying, for sure. More often than not I use canola oil to deep fry, but I have been known to deep fry eggplant, fish and other foods like Italian cooks I’ve watched. How do they taste? Pretty damned delicious.
But that’s sidestepping the health question–and this wasn’t the first time I’d heard “toxic” applied to cooking with olive oil. So I decided to lose the huffy attitude and find out where that idea was coming from. I’m not a Dr. Oz follower but it struck me as unlikely that he was out there demonizing olive oil. All right, the guy does talk about “belly blasting supplements” on his site. But he’s a highly trained cardiologist and he comes from Turkey, a Mediterranean country as saturated in olive oil as any other.
I found lots of blogger and consumer posts worried about the toxicity of olive oil, but no rants from Dr. Oz. On one site, he says reasonably, “Olive oil has been well studied. It’s more than okay to cook with it.” Studies about the dangers of cooking with olive oil often focus on commercial deep-frying practices, he points out: “It takes 10-15 reheatings to produce the really bad chemicals.”
- All oils degrade–that is, their cellular structures change in negative ways–when exposed to heat. Olive oil is average in this respect. The degree of damage depends on the temperature and duration of cooking.
- Most home cooking happens in a temperature range between 250°F and 350°F. If you’re deep frying, you might get up to 365°F. That’s well below olive oil’s smoke point of 410°F or higher, when toxic aldehydes (these are new to me, too) could form. Unless your smoke detector is screaming constantly, you’re in the safe zone.
- Heat can impair or destroy the polyphenols and other compounds on which olive oil’s reputation as a heart-healthy oil depends (refined oils don’t have these in the first place). So, if you’re consuming olive oil as a health tonic, it’s best to dress a salad or take a daily slurp instead of (or in addition to) sauteing a chicken breast in olive oil.
- Any oil continues to break down into potentially harmful components when reheated. If you’re a deep-frying fan, don’t re-use the oil more than once or twice.
- Tastings by experts indicate that many flavor and aromatic properties of a good olive oil will volatize and vanish when exposed to heat.
Those first four bullets confirm, to my relief, that cooking with olive oil is safe. But the last point about heated olive losing its flavor–that hurts my soul. It’s something I’d rather not believe, like those studies showing that imitation vanilla and natural vanilla produce the same baking results.
And yet respected food scientist Harold McGee says so, based on blind side-by-side tastings of 11 seed oils and 4 olive oils (the latter included two prize-winning extra virgins, an innocuous supermarket oil and a cheap bottle with off flavors). In a New York Times article, McGee’s experts reported that the heated oils all tasted “slightly nutty and fried.”
McGee concludes that there’s not a big flavor payoff for cooking in olive oil–and that, if you do, an inferior oil might produce results similar to a good one. His go-to cooking oil is canola. Mine is a mild but fruity Italian olive oil good enough to use on salads as well as for cooking. I get a price break by buying it in a three-liter tin–but even so it costs about six times as much as canola. Am I a sucker for cooking this way, I wondered?
I went to the kitchen and put my beloved olive oil through an impromptu faceoff with that ugly canola oil bottle from the pantry. There was just one taster: me, moving the cups around as in a dice game, with eyes squeezed shut. The differences were subtle, but in three out of three tastings, I picked my oil.
Bottom line, I’ll go right on cooking with olive oil. But this little inquiry made me realize that it might be equally logical to opt for the seed oil–and that our kitchen decisions depend as much on habit and emotion as on science.