Fats and cooking oil are made up of different  fatty acids: mono, poly, and saturated in varying percentages. The predominant  fatty acid within the oil will determine whether exposing it to heat, oxygen, light, or moisture will cause a stress to your health.

We generally advise that a polyunsaturated oil,  should NEVER be cooked with, these oils are high in omega 6 fatty acids and are highly reactive. It is ok to have small amounts raw.  Lipid (per)oxidation and free-radical production quickly takes place when they are exposed to heat – even very low heat. Peroxidation and free radicals  produce inflammation and irritation within our bodies, which in turn set us up for any and all chronic illnesses including autoimmune disease, heart disease, cancers and the list goes on. Your  omega 6’s oils will be protected when they are raw, organic, cold-pressed, and unrefined.

Cooking at higher temperatures is best done with  saturated oils like coconut oil, palm oil, butter, ghee, lard, and tallow.

For sautéing, avocado oil, macadamia nut oil, and olive oil are great.

Let’s look at Grape seed oil and rice bran oil.Here is a fatty acid profile for both:
Grape seed oil                            Rice bran oil
71% POLY                                  36% poly
17% mono                                  48% MONO
12% saturated                            17% saturated

Grape seed oil is mostly a polyunsaturate fat and should never be exposed to any degree of heat. Store it in the refrigerator and use sparingly.
Rice bran oil on the other hand, is predominantly a monounsaturate so it is a bit more stable and can be used at a  low-heat. Rice bran oil is still high in polyunsaturates (36%), so store it in the fridge and use in moderate amounts. Rice bran oil’s 17% saturated fatty acid content protects the delicate poly fatty acids when exposed to low-heat cooking. It shares a similar profile to sesame oil (43 poly, 42 mono, and 15 sat), so it’s best to follow the same rules for cooking with both rice bran and sesame oils, although sesame oil has a higher antioxidant profile for added protection.

If you add a bit of a saturated fat to any monounsaturated when cooking a light stir-fry or low-simmer dish you protect the poly content that particular fat may have. Mix sesame oil with coconut oil for oil pulling, an effective and traditional oral health secret.

Heat and polyunsaturated fats don’t mix! So using heat during the oil extraction phase damages the poly fat molecules. That means the oil is rancid before it gets to the supermarket.
Let’s take a look at the typical fatty acid profile of Avocado and Macadamia

Avocado                   Macadamia                          Olive
10% poly                  10% poly                              12% poly
70% MONO              78% MONO                         75% MONO
20% saturated          12% saturated                     13% saturated

Avocado and macadamia nut oils have a very similar amount of mono with  low poly content (especially macadamia oil), and decent saturated fatty acid content to help protect the more delicate poly and mono fats

Olive oil has the highest poly content of this group, so needs to be kept cool and is probably best poured into foods after cooking, or on a low heat quickly.

Peanut oil is another type of monounsaturated dominant oil, but it also has 34% poly fats in its profile, so has limited use, and it is best to avoid heat here.

Corn, safflower, sunflower, flax (linseed), walnut, hazelnut, hemp, pine nut, pumpkin, and wheat germ oils should only be used raw and in small amounts. Keep in the fridge.

Always look for cold-pressed, unrefined oils.

Cottonseed oil, canola oil, and any refined hydrogenated oils along with trans fats should always be avoided. These fats are anti-nutritive, denatured, highly processed, pesticide and solvent laden, rancid.  NO AMOUNT OF TRANS FATS is safe.

Caroline is a Board Certified Nutritional Therapist (NTP) ,located in Long Island, NY
Sources:
Fats that Heal, Fats that Kill – Udo Erasmus
The Skinny on Fats – Dr. Mary Enig and Sally Fallon – Morell
Know Your Fats – Dr. Mary Enig