Leisha I love olive oil, but you will rarely see us cooking with it at Living Ground. We use good extra-virgin olive oil generously on salads, vegetables, herbs, cheeses, fermented foods, soups and finished dishes, but when a pan goes onto the stove, we reach for butter, coconut oil or tallow. I am always surprised when someone tells me they use olive oil to cook with. Hence the reason I am sharing this information.
There is a simple reason for this. Extra-virgin olive oil contains far more than fat, and many of the compounds that make it such an extraordinary food are sensitive to heat. If I have a beautiful bottle of fresh, peppery olive oil, I want to eat those compounds, smell them and taste them, not use them as fuel for a frying pan. I want the benefits of olive oil.
Olive Oil Is More Than Oleic Acid
Olive oil is rich in oleic acid, a monounsaturated fatty acid that is actually quite resistant to oxidation compared with highly polyunsaturated oils. Good extra-virgin olive oil also contains a collection of plant compounds including hydroxytyrosol, tyrosol, oleocanthal, oleuropein derivatives, lignans, tocopherols, squalene, pigments and aromatic compounds.
These compounds help give fresh olive oil its bitterness, green fragrance and that lovely peppery sensation that can catch in the back of your throat. They are part of the living chemistry of the olive fruit, and they are a large part of what separates a beautiful extra-virgin olive oil from a bottle of refined fat.
So when someone asks me, “Can I cook with olive oil?” my answer is not based simply on whether the fatty acids survive the heat. I want to know what happens to everything else in that oil as well.
Heat Changes Olive Oil
Heating any fat begins changing its chemistry. Temperature, oxygen, cooking time, moisture and repeated heating all influence what happens, and higher temperatures generally speed those reactions.
Studies examining virgin olive oil under cooking conditions have found significant reductions in some of its phenolic compounds. Hydroxytyrosol and related compounds are particularly sensitive, while lignans appear to withstand heat considerably better. Tocopherols can also decline with prolonged heating.
A 2022 review examining the effect of cooking on olive-oil phenols found that the outcome varies considerably with temperature, cooking method, the food being cooked and the particular oil being studied. The researchers still noted a general nutritional preference for extra-virgin olive oil being used at lower temperatures for shorter periods when the goal is preserving its phenolic compounds.
That is enough for me to make a very simple kitchen decision. I do not buy good olive oil because I need something slippery in the frying pan, so I would rather keep it out of the pan altogether.
But Olive Oil Has a High Smoke Point
Smoke point gets brought into nearly every discussion about cooking oils, but smoke point is only one measurement. An oil does not remain chemically unchanged until it reaches one magical temperature and then suddenly deteriorate.
Chemical changes are already occurring during heating, and the degree of change depends on much more than smoke. Fatty-acid composition, phenolic content, antioxidants, oxygen exposure, temperature and length of cooking all contribute to what happens in the pan.
Extra-virgin olive oil actually performs surprisingly well in thermal-stability studies because oleic acid is relatively stable and its natural antioxidants offer some protection. Research has shown that several components, including oleic acid, sterols and squalene, remain quite stable during heating, even while some phenolic compounds and tocopherols decline.
So I am not telling you that olive oil immediately becomes poisonous when it gets warm. I am saying something much simpler: heating a beautiful food changes it, and some of the compounds I specifically want from olive oil are among the compounds affected by that heat.
The Phenols Are Part of the Prize
Hydroxytyrosol is one of the phenolic compounds associated with extra-virgin olive oil, along with tyrosol and a much larger family of related plant chemicals. When virgin olive oil was subjected to simulated domestic cooking conditions in laboratory research, heating at 180°C significantly decreased hydroxytyrosol-like and tyrosol-like substances.
Other research has found substantial losses of phenolic compounds during frying, with temperature playing an important role. Reviews of the literature describe decreases in several phenols as heating becomes hotter or longer, even while acknowledging that olive oil remains relatively resistant to oxidation as an oil.
Those two facts are not contradictory. The basic fatty-acid structure of olive oil can be reasonably heat stable while some of its more delicate plant compounds are being reduced or transformed.
That distinction gets lost in arguments about whether olive oil is “safe for cooking.” Safe is not the only question I am interested in asking about food.
What Are We Trying to Preserve?
Imagine buying fresh garden herbs and then boiling them for hours before eating them. You would still have plant material in the pot, but you would not expect every aromatic compound in those herbs to remain exactly as it was when you picked them.
I think about olive oil in much the same way. A fresh extra-virgin olive oil is a plant extract produced mechanically from a fruit, carrying volatile compounds, phenols, pigments and flavours that tell us something about the olive variety, its ripeness, the harvest and even the land where the tree grew.
Heat changes some of that complexity. Research looking at olive-oil antioxidants and cooking has consequently suggested adding EVOO to vegetables after cooking or toward the end of preparation when preservation of these compounds is the priority.
That makes far more sense to me than pouring beautiful olive oil into a hot skillet.
Use a Cooking Fat for Cooking
In our kitchen, we keep this very simple. For frying and cooking we use fats such as tallow, butter and coconut oil, choosing according to the food we are making.
Then we use extra-virgin olive oil where I think it shines. We pour it over the food after cooking, use it in dressings and pestos, drizzle it over soups and vegetables, mix it with fresh herbs, add it to cheeses and fermented vegetables, or simply eat it with good bread and sea salt.
A plate of warm vegetables finished with raw olive oil is completely different from vegetables that spent twenty minutes frying in it. You still get the richness of the oil, but you also retain more of the fragrance, bitterness, pepperiness and complexity that made you buy extra-virgin olive oil in the first place.
Follow the Olive Back to the Soil
There is another reason I have so much respect for olive oil. Before there was a bottle, there was a fruit, and before there was a fruit, there was an olive tree living in relationship with an entire biological world beneath its feet.
The roots of that tree exist inside a rhizosphere filled with bacteria, fungi, protozoa, nematodes, microarthropods and countless other organisms. Minerals cycle, organic matter decomposes, fungal threads explore the soil, roots release carbon compounds, microbes transform nutrients and the tree participates in this living exchange.
The olive forming above ground is connected to everything happening below it. Soil structure, water, mineral cycling, microbial relationships, climate, genetics and the physiology of the tree eventually become part of the chemistry expressed in the fruit.
Then we crush that fruit and collect its oil. Something that began with sunlight, carbon, soil, water, microbes and plant metabolism ends up shimmering green-gold on our plate.
That deserves a little respect in the kitchen.
Fresh Olive Oil Is Alive With Aroma
If you have only eaten supermarket olive oil that has sat around for a very long time, fresh olive oil can be a revelation. Depending on the variety and harvest, it may smell of cut grass, herbs, green tomato, artichoke, fruit or leaves, and it may finish with bitterness or a peppery catch in the throat.
Many of those aromas come from volatile compounds, and volatile compounds are, by their nature, easily changed or lost. Heat accelerates that loss, which is another reason cooking can flatten some of the sensory character of a beautiful oil.
I want those volatile compounds reaching my nose as I lift the fork. Flavour is part of nutrition because eating is not simply a process of delivering calories into a digestive tract; it is an interaction between plants, chemistry, microbes, senses and the body receiving the food.
Olive Oil Does Not Need to Be Feared
There has been so much confusing information about fats that people often want a simple classification: good oil or bad oil, safe oil or dangerous oil. Olive oil does not need that kind of fear-based treatment.
Good extra-virgin olive oil is an extraordinary food. Its predominantly monounsaturated fatty-acid profile gives it considerable oxidative stability, and the scientific literature certainly does not support the claim that merely warming olive oil instantly turns it into something toxic.
My recommendation not to cook with it comes from the opposite direction. I value it too much.
Why take an expensive, beautifully made, phenol-rich extra-virgin olive oil and repeatedly expose it to heat when there are other fats perfectly suited to cooking? Keep the olive oil for the part of the meal where you can actually experience what makes it special.
My Kitchen Rule
Our rule at Living Ground is easy to remember. Cook with butter, coconut oil or tallow, and use good extra-virgin olive oil raw or add it after the cooking is finished. We do offer seed oil, sunflower, for the vegans and vegetarians but I wish we didn’t
For olive oil, drizzle it over roasted vegetables once they leave the oven. Pour it into soup just before serving, blend it into pesto, whisk it into a fresh dressing, spoon it over tomatoes and herbs, mix it into fermented vegetables, or let it soak into a beautiful piece of bread.
You do not need to be frightened of olive oil and you do not need a chemistry degree to use it well. You simply need to recognize that the olive gave is great raw. When I open a bottle of beautiful extra-virgin olive oil, I want as much of that olive as possible to reach the plate. The tree, the soil, the fruit, the aroma, the bitterness, the phenols and the peppery little kick in the throat are all part of the gift, so I choose not to cook them away.
References
Ambra R, Lucchetti S, Pastore G. “A Review of the Effects of Olive Oil-Cooking on Phenolic Compounds.” Molecules. 2022;27(3):661.
Allouche Y, Jiménez A, Gaforio JJ, Uceda M, Beltrán G. “How Heating Affects Extra Virgin Olive Oil Quality Indexes and Chemical Composition.” Journal of Agricultural and Food Chemistry. 2007;55(23):9646–9654.
Brenes M, García A, Dobarganes MC, Velasco J, Romero C. “Influence of Thermal Treatments Simulating Cooking Processes on the Polyphenol Content in Virgin Olive Oil.” Journal of Agricultural and Food Chemistry. 2002;50(21):5962–5967.
