Are they pulling the ‘OIL’ over your eyes


This post aims to clarify how the oils you can buy are produced and how to tell good quality oils and be confident they will not damage your health.  

Seed Oils

These are all the type of oils you are being offered on the shelf in your local supermarket, don’t assume that all oil is equal so read the labels and ingredients carefully, a lot of oil is blended.

Cold pressed

This term means that the seed is extracted using a screw press, but the seed is not pre cooked to break down the cell structure and release more oil.  That does not mean that temperatures reached in this process are not high enough to start the breakdown of EFAs.  Cold pressed should mean quality oil, but in fact is often used on oil labels where the oil has been Refined (See below).

How can you tell unrefined oil? There is an easy infallible test – if it doesn’t smell and taste of the seed that came from, it has been refined.  

Unfortunately many of the “cold pressed” oils on the shelf have been refined, which involves some pretty nasty processes. (read on…)  

Expeller Pressed


The oil is extracted by a screw press and may or may not have been cooked, so the term is often used instead of cold pressed.  So while there has been no solvent use, it does not mean the oil has not been refined.

Solvent extracted 

Oils like soy, rice bran, grape seed and corn on the supermarket shelf are usually extracted the “modern” way, using an oil based solvent because this method is capable of cheaply extracting oil from low oil containing sources like these.

Hexane is the main solvent used and is a cheap byproduct of petroleum refining, so it’s a perfect solution to use it to extract oil from seeds cheaply – it surely doesn’t matter if it leaves a small residue in the oil?  Well maybe it is a neurotoxin, which can give the glue sniffers the high they are after – but hey?  


Refined oils

Most oils in the supermarket have been through the whole industrial process which involves: 

Cleaning & Cooking: 

The seeds are mechanically cleaned and then cooked at temperatures well over 100°C. This breaks down the cell structure to aid oil extraction, but such high temperatures start the oxidation process. 

Oil extraction:

The cooked seeds are expeller pressed at high pressures and temperature and the seed cake is then solvent extracted. The damaged oils which result from these processes need to be cleaned up so that they are palatable. 


Phosphoric acid and water are mixed with the oil to strip out the lecithin (which helps your body to digest oil), minerals and chlorophyll. 


Caustic soda or soda ash are added to settle out the damaged fats, waxes and phospholipids which can promote oxidation. But these two steps also take any naturally occurring antioxidants like Vitamin E or A. 


Fullers earth, activated clay or activated carbon are used to remove the last of the soaps and protective pigments. These three steps are all done at high temperatures, which cause substantial oxidation of the EFAs. 


Steam at destructively high temperatures and pressures is passed through the oil to remove all the volatile flavour components, some of the damaged oil fragments and any remaining natural antioxidants. 

What is left is a pale, bland flavourless, oil which contains damaged EFAs and is extremely susceptible to oxidation. 

Of course light is extremely damaging to oils, so to allow such oils to be put on the supermarket shelf in a clear plastic bottle, a synthetic antioxidant is added – many of these are suspected to promote cancer. 


What does this mean for the health of you and your children?

Refined oils are similar to white flour and white sugar in that they are empty calories with none of the cofactors needed for healthy metabolism.  

Yes, they do contain some undamaged Omega-6, but most people have way too much Omega-6 in their body anyway and you seriously need to cut down on the amount you eat.  

These oils also contain nasty byproducts of the refining process so are actively damaging to your health – your body uses the fats present in your bloodstream to make millions of new cells each day so you need to eat only undamaged fats.  

So what are your options for getting healthy undamaged oil from the supermarket?


The Good Oils to Cook with:

If you can find unrefined Macadamia, almond or canola oil they are high in Omega-9 and good to use.  

However there are really only two readily available options – Olive oil or Avocado oil and of these only the Virgin or Extra Virgin have not been solvent extracted or refined.  

These two oils come from the flesh of the olive or avocado, so are extracted by a very different method.  For supermarket oils the fruit is ground to break down the cell structure and churned to release the oil.  The fibre and juice are separated from the oil by a sophisticated centrifuge.  

The different grades are:  

Extra virgin

Solvent extraction is not permitted for virgin labeled oils.  Because there can be a lot of oxidation during the grinding and churning process, only oil that has been tested to have low damage and superior taste can be called extra virgin.  



Non solvent extracted oil which has lesser taste and higher levels of oxidation – but still good oil.  


This is a rather misleading name as you could think that this means lower calorie/fat which it isn’t. It is solvent extracted from the pomace after the virgin oils and has been refined so that it has no flavour components left. Not a healthy oil.  

The Good Oils Not to Cook with:

The unrefined nut and seed oils with high levels of Omega-6 – see Omega-6 blog, should not be used for cooking. Cooking exposes them to heat, light and oxygen all at once and the Omega-6 molecule is much more easily damaged than the Omega-9 molecule because of the extra double bond.  

Extra Virgin Flax seed oil is also a very healthy oil – see Omega-3 blog, but is even more easily damaged by cooking because Omega-3 contains 3 double bonds.  


Most oils in the supermarket have been so badly damaged in the manufacturing process that they are not fit to put into your body.
So don’t be fooled by the big letters saying ‘Cold Pressed’ – check the label to see if it is unrefined – if it doesn’t say unrefined assume it has been refined or try the taste.
The readily available good oils are Virgin and Extra Virgin Olive, Avocado and Flax Seed oils

Tip of the Day

A healthy and tasty  combination to use in cooking is about half and half butter and Virgin or Extra Virgin Olive oil (See Butter vs. Margarine blog)  


Check out the best oils at


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