Healthy Cooking Oils and Other Food Preparation Factors

How does cooking affect our food?

Heat depletes the nutrient content of foods. It modifies the protein, carbohydrates and fats into less effective, and sometimes harmful, compounds. Let us consider the impact on PUFAs.

Cooking food in fat or oil changes the overall PUFA content in several ways:
The degree and complexity of the changes depend on the cooking method.


Frying causes the largest changes because of the high temperatures involved and the interactions that take place between the food and the cooking oil.

Do not fry food using oil rich in PUFAs: Avoid using oils that contain high levels of omega-3 or omega-6 PUFAs for frying because they are highly prone to oxidation due to their high levels of unsaturation. Oxidation produces free radicals and other compounds that are detrimental to your health.

Fats and oils that are high in saturated fatty acids and monounsaturated acids are more suitable for frying because they are more stable when heated. Use coconut oil, palm oil, butter, cocoa butter, olive oil or canola oil.

From a PUFA perspective, frying is much more complex than baking or grilling because:
If you fry food frequently you may wish to consider:

Baking, roasting and broiling (grilling)

Baking, roasting and broiling (grilling) food generally have less impact on its PUFA composition than frying. The same principles apply in terms of which types of oil to use.

Does it matter which type of cooking oil we use?

Apart from the issue of instability described above, research has shown that the type of cooking oil used directly affects the ultimate PUFA content of the cooked food (Chow 531). Deep-frying in olive oil enriches the food in oleic acid while deep-frying in sunflower oil enriches the food in LA, therefore impacting the omega-3 to omega-6 ratio adversely.

Choose your cooking oil with care: Frying foods in corn, sunflower, safflower or soya oil enriches the food with LA, resulting in an adverse omega-3 to omega-6 ratio. Choose palm oil, butter, olive oil, canola oil, rapeseed oil or coconut oil to help maintain a more healthy PUFA balance.

In Mediterranean countries around one half or more of fat consumed comes from cooking oils and fats (Chow 531). The type of oil used for cooking is therefore an important health factor.

Cooking oils

Here are some oils commonly used for cooking (Chow 228-229):

Cooking Oils ALA % by weight of total Fatty Acids LA % by weight of total Fatty Acids n-3 to n-6 Ratio
Coconut Oil 0.0 1.5 NA
Canola Oil 9.2 18.7 1 to 2.0
Rapeseed Oil 7.3 14.6 1 to 2.0
Soybean Oi 7.8 53.2 1 to 6.8
Olive Oil 0.6 10.0 1 to 16.7
Palm Oil 0.3 9.4 1 to 31.3
Corn Oil 0.9 57.0 1 to 63.3
Sunflower Oil 0.5 68.2 1 to 136.4
Cottonseed Oil 0.3 53.3 1 to 177.7
Sesame Oil 0.2 43.3 1 to 216.5
Peanut Oil None 31.4 NA
Safflower Oil None 77.7 NA

You can improve your omega 3 to omega 6 balance by using canola, rapeseed, olive or palm oil instead of oils that have a much higher LA content.

Although coconut oil has no ALA, it has one of the lowest LA contents and has other advantages, including very good heat stability and high resistance to rancidity due to its high saturated fat content.

Canola and rapeseed oil have the best omega 3 to omega 6 ratios. Olive oil and palm oil are even lower in LA content although they contain very little ALA and hence have a less well balanced omega 3 to omega 6 ratio.

Refer to The Omega Diet by Artemis Simopoulos for a good comparison of canola oil and olive oil, both of which are recommended by her.

Read a review of Artemis Simopoulos's book The Omega Diet