I've heard that cooking with olive oil is bad for you and can be toxic. Is this true? If so, to what extent?

I see no warning on the container of my olive oil that states that it would be bad to cook with olive oil.

  • 1
    Depends on how you cook it. While olive oil is monosaturated and considered a very good/healthy oil, it also has a pretty low "smoke point." When oils burn/smoke, their structure breaks down, and you get a lot of damaging free radicals, but I think that's generally if you're trying to do something like fry with oils, not general sauteing. Aug 30, 2016 at 19:58

3 Answers 3


I think this is a problem with all oils. When something burns, it produces smoke. Smoke is generally indicative of something that isn't particularly good for us if inhaled. Same holds for oils. It seems that all oils will begin to produce toxins once they hit their smoke point. However, before that, they are completely fine. So pick an oil that will handle the temperature you're using by checking the smoke point.

There's also a difference between producing toxins and toxic. Does burning oil produce toxins? Yes. Will that actually make you sick? I don't know. But my inclination is that it's unlikely to cause you harm under "normal" usage or else we'd be hearing about people actually getting sick from burning their oil rather than just getting scare stories on the news about free radicals.

And to get very sciency (stop reading immediately if your eyes glaze over, I think that's a sign of toxicity), from biology online:

Researchers investigated processes of oxidative degradation - notably that caused at 70°C with ventilation - of a broad group of oils with very wide-ranging compositions. Another degradation process studied was that which is caused by microwave action that does not heat greater than a temperature of 190°C.

In both processes deterioration of the oils takes place. In the first type of process (70°C with ventilation) hydroperoxides are first produced and subsequently aldehydes. In the second kind of process (microwave) it is basically aldehydes produced. It has to be pointed out that both the oxidative conditions and the composition of the oil determined the velocity of the degradation and both the nature and concentration of the compounds produced.

These studies have shown, for the first time, that degradation of lipids in foods can produce toxic oxygenated aldehydes. These compounds, well-known in medical studies for their geno- and cytotoxic activity, considered as markers of oxidative stress in cells as well as being causal agents of degenerative illnesses, had not previously been detected in foodstuffs.

Researchers have shown that some oils produce these toxic substances in greater quantities and at a greater rate. Virgin olive oil was, amongst all the oils studied, that which took longer to produce this type of compounds and produced a lower concentration of them.

  • 1
    at the end, it looks like olive oil wins for being able to smoke the longest, if that's a good thing...
    – justkt
    Aug 27, 2010 at 13:24
  • Very informative answer. :-)
    – Chris
    Aug 27, 2010 at 13:24
  • 2
    Beat me to it! Agreed about the "we'd be hearing about it more". +1, wish I could +2 for the science part. Aug 27, 2010 at 13:26
  • Mediterranean cuisine always used olive oil; now I know the scientific reason behind that.
    – apaderno
    Aug 27, 2010 at 14:21
  • See also cooking.stackexchange.com/questions/13132/…
    – tog22
    Mar 24, 2015 at 20:49

General consensus seems to be that heating oils beyond their smoke point - which is generally low for olive oil - causes free radicals to form and can be toxic. Here's a summary of that information. So if you need to cook to high heat, you probably want to go with a higher smoke point oil like peanut.

There appears to be some research that highly unsaturated oils held at high heat for a long time can begin to break down into a toxic substance known as HNE. This research comes out of the University of Michigan. While olive oil is highly unsaturated, it wasn't mentioned specifically in this study.


The problem is that smoke points are not as simple as one would think. The smoke point of an oil varies from sample to sample. That is why the smoke point of olive oil is usually represented as a range.

Extra virgin olive oil smoke point range 350⁰ - 410⁰ F Olive oil and light-tasting olive oil smoke point range 390⁰ - 470⁰ F

For comparison sake, a normal home cooking temperatures are between 350 and 375⁰ F. So generally, olive oil has a high enough smoke point to cook with. http://blog.aboutoliveoil.org/olive-oil-smoke-point

  • There are techniques beyond 190°C that some use at home (mostly wok cooking), but people using them tend to know that olive oil is not the best choice for these recipes :) Aug 31, 2016 at 8:56

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