Olive oil’s reputation has been besmirched. It isn’t the magic life elixir fueling the teeming hordes of Mediterranean-dieting, crusty bread-eating, moderate wine-drinking centenarians, but it doesn’t deserve to be tossed in the trash heap with soybean, grapeseed, corn, and canola oils. I sense that it’s fast becoming a “fallen fat” among our crowd and I think it’s a darn shame. Are a few extra grams of linoleic acid, one or two unfortunate incidents of adulterated oil, and gushing praise from vegans, vegetarians, and the American Heart Association alike enough to turn us against a staple, phenolic-rich food sporting several thousand years of storied history?
Allow me to explain myself. Early this week, I got an email from a reader: “I often roast my veggies with EVOO. Would butter be a better alternative, or are the fats in EVOO just as well?” This is an extremely common, totally innocent question. I get similar questions a few times each week. Moreover, I’ve noticed a general undercurrent across the paleosphere of folks avoiding olive oil altogether, either because it isn’t necessary for health, has too much linoleic acid, or it’s too prone to oxidative damage when exposed to the elements (heat, oxygen, light). I’d like to address each of these, particularly the oxidative stability. And I’ll answer whether I think we can cook with it or not.
Now, you don’t need to eat olive oil to be healthy – agreed. I would enjoy life less without good extra virgin olive oil, but I could be healthy without it and I can see why people would find it unnecessary. Besides, good olive oil can be hard to find or expensive, while a slab of good grass-fed butter is almost always more affordable.
Olive oil does have a fair amount of linoleic acid, with some varieties reaching concentrations of 20%. Using such a variety for the majority of your added cooking and salad fat – especially on a high-fat Primal Blueprint eating strategy – would mean eating excessive amounts of omega-6. Note, though, that some olive oil varieties are far lower in linoleic acid, and most extra virgin olive oil runs about 10%. Two tablespoons of the average stuff gives you about 2.8 grams of linoleic acid. That’s less omega-6 than most lard and poultry fat, if you’re counting, especially if you use it sparingly as a drizzler or in salads.
As for the oxidative potential of olive oil, that depends on a few things. Your olive oil is only as unstable as its environment. Heat, light, and exposure to oxygen all impact the oxidative stability of olive oil, as does the presence of antioxidants and phenolics. Of course, this is all works in a dose dependent manner; the more heat, light, and oxygen exposure, the greater the oxidative potential, while the more antioxidants and phenolics present, the lower the oxidative potential. Ultimately, it’s up to you to source good quality oil and store and handle it properly. If you buy your olive oil at Costco in two-gallon clear plastic jugs, don’t be surprised when it doesn’t hold up as well as the extra virgin deep green olive oil that leaves streaks of olive sediment behind and burns your throat going down. If you store your olive oil next to the stove, often forget to secure the cap, and expose it to plenty of kitchen lighting, it’s not going to last very long.
Surely heating such a fragile plant oil will render it inedible, toxic, and liable to result in oxidized serum lipids if eaten. Right? Not so fast. While subjecting extra virgin olive oil to high heat can alter the taste, it’s actually fairly resistant to oxidative damage from cooking. Let’s take a look at some studies to make sure:
In one study, the authors heated various oils to “deep-frying conditions” and checked oxidative markers every three hours. The olive oils made it 24-27 hours of constant high heating before reaching the maximum legal value of heat damage. Not bad, and it’s not like you’re going to use your olive oil to deep fry anyway.
Despite being heated at 180 degrees C (356 degrees F) for 36 hours, two varieties of extra virgin olive oil exhibited strong resistance to oxidative damage and retained most of their “minor [phenolic] compounds.”
But then there’s this study, in which subjects were given heated olive oil meals, heated safflower oil meals, unheated olive oil meals, and unheated safflower oil meals. Both of the heated oils and the unheated safflower oil resulted in elevated postprandial oxidative markers, while eating unheated olive oil resulted in none. Note, though, that the olive oil was probably refined or light (otherwise they would have called it “virgin” or “extra virgin”) and thus devoid of significant phenolics with antioxidant properties. Also, the oils were heated at 210 degrees C (410 degrees F) for eight hours, which seems excessive. The home cook sauteeing some shrimp and onions in white wine and EVOO is unlikely to hit 210 degrees C, let alone stay there for eight hours.
You’re probably aware of the oft-cited benefits of olive oil on blood lipids. Namely, that it raises HDL and lowers LDL. You’re probably rightfully skeptical of the relevance of these changes in numbers. I am too, so let’s not talk about those. But how do you feel about oxidized LDL? Many are beginning to suspect that a causal link between oxidized LDL and atherosclerosis exists, and I think everyone agrees that reducing the oxidative potential of our lipoproteins is a good thing. The story as commonly told is, roughly, that unsaturated fat-rich LDL are inherently unstable and prone to oxidative damage, so eating a lot of unsaturated fats will mean vulnerable LDL and eating lots of saturated fats will mean stable LDL. Since the primary fat in olive oil is the unsaturated monounsaturated oleic acid, the common idea is that eating too much olive oil will make LDL vulnerable to oxidation like the other unsaturated fats.
So, what does the research show?
Most studies show that extra virgin olive oil either reduces measurable oxidized LDL or reduces measurable markers for oxidized LDL in humans. Dietary extra virgin olive oil reduced the number of oxidized LDL and increased HDL in proportion to the phenolic content of the oil; the more phenolics, the greater the effect. Tested LDL was also more resistant to oxidation after being removed from subjects and exposed to oxidative stress. Similar effects were found in a more recent study, in which men were given either EVOO with high phenolic content or refined olive oil with zero phenolics present. Men consuming high phenolic EVOO had less oxidized LDL and more phenolics present in LDL, indicating that dietary phenolics reach serum LDL and exert antioxidant effects in vivo.
A possible mechanism behind reduced oxidized LDL looks like an increase in oxidized LDL antibodies. In one randomized clinical trial, healthy men were given 25 mL of olive oil of varying phenolic content per day; a greater capacity for antibody production corresponded with higher phenolic intakes.
The proof, as they say, is in the pudding. Most evidence points to extra virgin olive oil being a highly nutritious, healthy addition to a diet. And for all the hand wringing about extra virgin olive oil being way too unstable to have around on a regular basis, let alone actually willingly ingest, it even appears to be protective against LDL oxidation when consumed in the pure, extra virgin, high phenolic, room temperature state (and even reasonably heated it doesn’t seem too shabby, either). From what I can tell, it does the exact opposite of what some people worry it will do to their blood lipids. For that reason, I think olive oil deserves another look. A fresh start, perhaps?
Let’s put it to rest – olive oil, especially good quality virgin olive oil with all the phenolics intact, is decently resistant to heat-incurred oxidative damage and a great addition to your diet. And if you’re worried about exposure damage, adding a bit of vitamin E to olive oil seems to reduce oxidation. (Furthermore, rats who ate the vitamin E-dosed oil exhibited fewer signs of oxidative stress in vivo than the rats who ate the unenriched olive oil, so it’s not just cosmetic; it actually has an impact on how the food is processed in the body.) Keep your intake moderate, don’t use it as a frying staple, choose the good stuff, and try to use it mostly at room temperature. I find that the culinary benefits of extra virgin olive oil (the taste, the pepperiness, the subtle depth) and the nutritional benefits (the phenolics, primarily) become heightened when added at room temperature (or at the most gently warmed) to dishes. I love butter and ghee and coconut oil as much as anyone, but the undercurrent of fear surrounding the exposure of olive oil to slightly elevated temperatures and to oxygen is unfounded and, in my opinion, misguided.
The bottom line? If you’re making a tomato-and-meat-based sauce to go over spaghetti squash and you want the traditional Italian flavor, don’t worry about a bit of extra virgin olive oil going rancid due to some heat exposure. Give it some EVOO love. You and it will survive the journey intact.