From the home cooks new-found enthusiasm for coconut oil to restaurants deep frying with “healthy” vegetable oil, there has been a lot of debate over which oils are the best cooking oils.
The fact is that some oils degrade when exposed to heat, which makes them bad choices for cooking.
In this article and video, I explain which oils to include as part of your healthy low-carb or keto lifestyle, and which ones to avoid.
Categorize Cooking Oils
Cooking oils are best categorized by their level of saturation.
So, we think of them as being either saturated, monounsaturated, or polyunsaturated.
The more saturated a fat is, the more stable it remains when subjected to heat.
Tropical oils, like coconut oil and palm oil, contain a lot of saturated fatty acids.
Vegetable oils, like soybean, corn, and sunflower oil are highest in polyunsaturated oils.
Other commonly used oils, like olive oil, avocado oil, and canola oil contain mostly monounsaturated fatty acids.
Oils Contain a Mix of Fatty Acids
You may have noticed that I said these oils contain mostly saturated, monounsaturated, or polyunsaturated fats.
The reason I worded it that way, is because all oils contain a mix of different fatty acids.
For instance, let’s take a look at the USDA Food Composition Database (1).
Looking at this chart, we see that soybean oil, which is the most frequently used polyunsaturated vegetable oil, contains more than 15 grams of saturated fat per 100-gram serving.
We also see that olive oil, which is an oil that is classified as monounsaturated fat, contains more than 13 grams of saturated fat per 100-gram serving.
Saturated Fats Have an Undeserved Bad Reputation
It might be surprising to you that saturated fatty acids are found in soybean and olive oils.
There is no doubt that saturated fats have gotten a bad reputation over the years, but the current research shows that saturated fats are not the problem they were once thought to be.
This point is backed up by a systematic review study published in August of 2015 (2).
Systematic review means that a group of researchers read and reviewed all of the important studies on saturated fats and health to get the big picture.
Their conclusion was that “Saturated fats are not associated with a higher risk of all-cause mortality, CVD (cardiovascular disease), CHD (coronary heart disease), ischemic stroke, or type 2 diabetes.”
Saturated Fats: Heros or Villains?
Despite the fact that saturated fats have been exonerated of their evil status in many research papers, the public perceptions that saturated fat is a bad fat is hard to get away from.
However, in my opinion, it is about time we take a new look at saturated fats.
Saturated fats are the only oil that remains stable when exposed to heat and, therefore, oils that are high in saturated fats are the best cooking oil.
What Does It Mean To Be a Stable Oil?
Let’s take a little closer look at what it means to be a “stable oil.”
When you evaluate an oil for cooking, the main factor to consider is how well the oil tolerates heat.
You do not want the oil to break down or oxidize when it is exposed to heat.
This is because if the oil oxidizes, the fatty acids in the oil degrade into oxidation products.
Some of these oxidation products are called, free radicals, and they cause damage to your cells.
Saturated Fatty Acids are the Most Stable Fats
Whether or not oil will oxidize has everything to do with how saturated the molecule is.
Basically, the more saturated the oil is, the less opportunity it has to react with oxygen or oxidize.
Side Note: I went into the chemical structure of different fats in a video on my YouTube channel earlier this year. You can check that out here.
As a brief chemistry recap:
A saturated fatty acid has no available bonds around its carbon atoms to grab hold of another atom.
So, when we look at the molecule, we see that the four hands of the carbon are all joined to an atom already.
There is no available bond (or hand) to reach out and grab another atom.
In other words, there is no opportunity for an oxygen atom or extra hydrogen atom to sneak in and cause the fatty acid to change.
This means a saturated fat molecule is stable.
The stability of the saturated fat molecule protects the molecule from heat-induced damage.
It also makes saturated oils, like palm oil, coconut, and even MCT oil, (which is derived from coconut oil), good choices for cooking even at high temperatures.
Polyunsaturated Fat Molecules are the Most Unstable Fats
On the other hand, polyunsaturated fatty acids contain two or more double bonds, and it is these double bonds that are prone to oxidation.
Think of those bonds as hands, so that double-bonded carbon can reach out one of its hands and grab hold of an oxygen atom.
In other words, it is prone to being oxidized or changed …AND… the risk of oxidation increases with two things:
- The number of double bonds present in the fatty acid
- The addition of heat
Polyunsaturated fats, like vegetable oils, have multiple double bonds in their structure.
This means that they are the most unstable oils when exposed to heat, and therefore the oils to avoid when cooking.
Monounsaturated Fats are in the Middle
Monounsaturated fats, like olive oil, only have one double bond.
So they can tolerate some heat, like low-temperature sauteing.
Which Monounsaturated Fats are Okay to Use?
When it comes to figuring out which monounsaturated fats are okay to use, I tend to look at the smoke point of the oils.
Olive oil has a low smoke point, so I only recommend it for non-cooking purposes, like salad dressings.
Avocado oil has a higher smoke point than olive oil, which makes it more stable.
So I do use avocado oil for cooking.
Canola oil is another oil that has a lot of monounsaturated fats in it.
However, it is a very controversial oil that is extracted from the rapeseed plant.
Personally, I do not use it because it is a highly refined oil and the reports link it to inflammation and other conditions.
So, I leave canola oil on the shelf.
Which Oil is the Best Cooking Oil?
The bottom line is that the more saturated an oil is, the more heat it can tolerate.
When it comes to cooking with oil, Coconut oil, palm oil, and MCT oil are good choices and vegetable oils are poor choices. Avocado oil also gets a thumbs up as a monounsaturated oil with a high smoke point.
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Thank you for reading. I hope this information will help you reach your healthy goals!
- US Department of Agriculture, Agricultural Research Service, Nutrient Data Laboratory. USDA National Nutrient Database for Standard Reference, Release 28. Version Current: September 2015. Internet: /nea/bhnrc/ndl
- De Souza, Russell J., et al. “Intake of saturated and trans unsaturated fatty acids and risk of all cause mortality, cardiovascular disease, and type 2 diabetes: systematic review and meta-analysis of observational studies.” Bmj 351 (2015): h3978.
About the Author
Dr. Becky Gillaspy, DC graduated Summa Cum Laude with research honors from Palmer College of Chiropractic in 1991.