Here's a look at the basic differences between the three types of fatty acids that are found in all commonly available oils:
Saturated fatty acids pack together tightly, making oils that contain a large percentage of them extremely stable when exposed to heat and light. Oils that have a high percentage of saturated fatty acids are your best choice for cooking.
Monounsaturated fatty acids do not pack together as tightly as saturated fatty acids do. They are relatively stable when exposed to heat, so oils that contain a high percentage of monounsaturated fatty acids are a fair choice for cooking.
Polyunsaturated fatty acids do not pack together very well. They are unstable when extracted out of whole foods, so oils that have a high percentage of polyunsaturated fatty acids tend to produce significant amounts of free radicals when exposed to heat. These oils should never be used for cooking.
Oils that contain a high percentage of saturated fatty acids are more stable than those that contain a high percentage of polyunsaturated fatty acids. When exposed to heat and light during processing, storage, and use, oils that contain a high percentage of polyunsaturated fatty acids tend to contain more free radicals than oils that contain mainly saturated and/or monounsaturated fatty acids.
Coconut oil is by far the healthiest cooking oil. It’s true that about 92 percent of the fatty acids in coconut oil are saturated. What many have overlooked for years is that over two-thirds of these saturated fatty acids are medium-chain fatty acids (MCFA). MCFAs are different from other varieties of saturated fatty acids in that as soon as they enter your bloodstream, they are taken to your liver where they are converted to energy. While other dietary fats and even excess carbohydrates can be stored as fat in your cells, the MCFAs found in coconut oil provide an almost immediate source of energy and may actually speed up your metabolism.
The high percentage of saturated fatty acids found in coconut oil makes it extremely stable when exposed to heat. Unlike almost all other vegetable oils, coconut oil contains virtually no trans fats, and is highly resistant to free radical formation when used for cooking at any temperature. No other oil comes close to being as safe and healthy for cooking as coconut oil.
Please always choose coconut oil made without fermentation or heat (cold-pressed, virgin coconut oil).
Palm oil is second only to coconut oil in its ability to remain stable when exposed to heat. If you did not use palm oil when you were growing up, you might find its taste and odor to be objectionable.
Its high percentage of monounsaturated fatty acids makes Olive oil relatively stable when exposed to heat. For cooking, it is the next best choice after coconut and palm oil. If you have difficulty maintaining your ideal weight, use olive oil sparingly, as its monounsaturated fatty acids are quite long in structure, which makes them more prone to being stored as fat than short or medium chain fatty acids. Believe it or not, butter is less likely to cause weight gain than olive oil because it contains a high percentage of short and medium chain fatty acids.
Like olive oil, Avocado Oil has a high percentage of monounsaturated fatty acids, which makes avocado oil relatively stable when exposed to heat.
Because it has slightly more monounsaturated fatty acids than polyunsaturated fatty acids, Peanut oil is relatively stable when exposed to heat. If you use peanut oil, I recommend that you limit use to just a few times per month.
Sesame oil has almost equal percentages of monounsaturated and polyunsaturated fatty acids. It shouldn't be used for cooking on a regular basis, and should be used raw sparingly.
Although it contains a high percentage of relatively stable monounsaturated fatty acids, Canola oil goes rancid quite easily, and relative to olive oil, forms high concentrations of trans fatty acids. Canola oil consumption has also been linked to vitamin E deficiency and heart disease, especially when a person is not getting enough saturated fatty acids in his or her diet. Many recent studies recommend staying away from canola oil whenever possible.
Stay away from Corn, Sunflower, Safflower, and Cottonseed oil completely. All of them contain large percentages of polyunsaturated fatty acids. They also have high concentrations of omega-6 fatty acids, which can cause a variety of health problems.
Because of their high concentrations of unstable polyunsaturated fatty acids, it is not recommended to use Hemp or Flaxseed Oil in cooking. If their manufacturers have minimized exposure to heat and light with their processing and bottling techniques, a small amount of these oils in their raw forms can be a part of a healthy diet. But it's healthier to eat their seeds freshly ground.
Grape seed oil should also be avoided when cooking. As with most other vegetable oils, it contains a high percentage of polyunsaturated fatty acids which produce significant amounts of free radicals when exposed to heat.
Please Note: the fatty acid percentages listed above have been calculated using the nutrient profiles for each oil as listed under the USDA nutrient database.
Bottom Line: use primarily coconut and/or olive oil for your cooking and baking.