Welcome back! Last week, I reblogged a post from nutritionist Anne Baker about canola oil and why it should be avoided (see http://wp.me/p3RNDT-bW). It received a great deal of interest. One question, in particular, that came up was which oils were best for medium and high temperature cooking. I’d therefore like to reblog Anne’s recent post on just this subject which can be found on her website http://nourishholisticnutrition.com/choosing-the-right-cooking-oil/:
Sauteeing, stir frying, pan frying, baking, grilling…..each type of cooking subjects foods to different degrees of heat. Using the wrong oil for the job can change a healthful meal and into one that’s toxic. This is because heat damages oils and can make them unstable. Knowing the smoke point of each type of cooking oil is important because heating oil to the point where the oil begins to smoke produces toxic fumes and harmful free radicals. Knowing how the oil is extracted and processed is another aspect to consider.
What we lose when we heat delicate cooking oils
According to Udo Erasmus, author of Fats that Heal, Fats that Kill, all nut and seed oils (which most people use to cook with) are at their peak of nutrition in their raw state, so if we really want to obtain their full benefit we should never heat them at all. This is important because heat destroys the oil’s beneficial polyphenols  and there are some oils that are so delicate they should never be heated. There are others that are fine used for medium heat and only a couple that are suitable for healthful higher temperatures. In general high heating such as pan frying (don’t even think of deep fried!) requires an oil that is stable at high heat.
How the oil is extracted matters
Selecting the right healthy oil begins with how the oil is processed. There are two main ways oil is extracted from its source. Expeller (cold pressed), also known as mechanically pressed, or chemically extracted oils.
Expeller pressing is a chemical-free mechanical process that extracts oil from seeds and nuts. This method of oil extraction is an alternative to the hexane-extraction method used for many conventional oils. The temperature reached during pressing depends on the hardness of the nut or seed. The harder the nut or seed, the more pressure required to extract the oil, which in turn creates more friction and higher heat. There is no external heat applied during the expeller pressing. 
Cold Pressed oils are expeller pressed in a heat-controlled environment to keep temperatures below 120 degrees F. It’s important to note that while Europe has standards prohibiting temperatures above 140 ° the US does not mandate specific temperatures and many products sold as cold pressed are extracted at temperatures up to as high as 470°.
Chemical extraction is done for most mass market cheap oils such as corn, canola and soybean oils (these are inferior oils). This process typically involves extraction with toxic solvents such as hexane. These oils then undergo harsh treatment to remove the solvent. More chemicals, very high heat, and straining are used to deodorize and bleach the oils — rendering them inferior in taste, fragrance, appearance and especially nutritional quality.
With this knowledge, it behooves us all to pay attention to how the cooking oils are processed and stick to cold pressed or expeller extracted.
Since cooking oil charts all indicate temperature ranges instead of the cook top settings low, medium low, medium, medium high and high this can also cause confusion. The chart below shows the oven temperature to cook top conversions – which I find very helpful.
Gas Mark Fahrenheit Celsius Description
1/4 225 110 Very cool/very slow
1/2 250 130 —
1 275 140 cool
2 300 150 —
3 325 170 very moderate
4 350 180 moderate
5 375 190 —
6 400 200 moderately hot
7 425 220 hot
8 450 230 —
9 475 240 very hot
This chart should be accurate enough for all your cooking needs, though keep in mind the temperatures will vary between different types, brands, sizes of ovens, in addition to your locations altitude, temperature, humidity, etc. 
What about cooking with coconut oil, butter/ghee and even lard?
Extra Virgin Coconut oil can be expeller pressed and this is a higher quality oil and healthier since it’s not extracted using chemicals.
High heat cooking oils should be selected based on how resistant to oxidation they are. This is because when oils undergo oxidation, they react with oxygen to form free radicals and harmful compounds that you definitely don’t want to be consuming.
Saturated fats have only single bonds in the fatty acid molecules, monounsaturated fats have one double bond and polyunsaturated fats have two or more. It is these double bonds that are chemically reactive. Therefore, saturated fats, with no double bonds, are by far the most stable.
Coconut oil and ghee are good for high heat cooking.
Coconut oil is 92 percent saturated fat, which is higher than butter. Coconut oil is a plant-based food and therefore does not contain cholesterol. According to Dr. Joseph Mercola “50 percent of the fat content in coconut oil is a fat rarely found in nature called lauric acid. Lauric acid is a powerful virus and gram-negative bacteria destroyer, and coconut oil contains the most lauric acid of any substance on Earth!”
Ghee is made by slowly melting butter over a low heat. This separates the milk solid proteins that are skimmed off leaving a deep golden colored saturated butterfat. Ghee or clarified butter contains conjugated linolenic acid, which is known to aid the body in weight loss and helps to lubricate the body’s connective tissues. Because it is so rich in antioxidants and lacking in milk solids, ghee does not have to be refrigerated. Ghee has one of the highest flash points (485ºF) which make this oil the best choice for high temperature cooking.
While many people do cook with olive oil in researching this post I found that now many experts are advising against cooking with extra virgin olive oil and some even feel olive oil (not EVOO) oxidizes too much when heated – even in low to medium heat. The reason for this is that olive oil is a monounsaturated fat vs. highly saturated fat oils such as virgin coconut oil and ghee. If you want to use olive oil don’t use extra virgin and only use on low to medium heat.
Lard and tallow from grass fed animals are high in mono and unsaturated fats; which makes them good for high heat cooking. I prefer to use coconut oil or ghee because I do not eat these foods.
Nut and seed oils
Contrary to popular belief, peanut oil is high in polyunsaturated fat and that means unstable for high heat cooking. Macadamia nut oil is high in monounsaturated fat so this is a good oil for medium heat cooking.
I found conflicting advice on many of the seed oils; sunflower, safflower, sesame seed, grape seed oils as to whether these are safe and healthy for high heat cooking. The determine factor in terms of healthfulness is weather the oil is predominately polyunsaturated. Grape seed oil is 71% polyunsaturated.
Remember the best oils (most stable at high heats) are saturated and monounsaturated oils. Polyunsaturated oils are not stable and therefor not good for high heat cooking. The other concern with these types of oils is that is that many are processed using hexane extraction which makes them unhealthy. 
Here’s a chart to help you decide which oil is best of low, medium and high heat cooking:
And there you have it – Thanks Anne! I hope this was helpful. Chime in and let us know if you agree with these recommendations.