Updated: Mar 3, 2019
I was involved in a conversation the other day on fats. We exercise physiologists/fitness therapists have them often. It usually involves one of three subjects. Losing fat from your body, eating safe fats or what fats you should use for cooking. Any one of these subjects are difficult to process for most. You know lots of sciency stuff to talk about. But that’s what we are about to do in this week’s blog. Talk about the kinds of fats/oils that are good and bad for cooking and eating, but we’ll keep the sciency stuff to a minimum.
Have you ever left oil in a pan over high heat, only to turn around and find it billowing with smoke? Yeah me either but I Abet you know someone who did right? The point is, every cooking fat, whether its butter, lard, or oil, has a temperature at which it stops simmering and starts to smoke. That’s called the smoke point, and learning how to interpret those points is a crucial element of any cook's vocabulary, even recreational ones.
Of course it’s not just the smoke we have to worry about when we overheat oil, or the kitchen fire that comes right behind it (well actually we do have to be concerned about that one). When oil is heated past its smoke point, the fat in the oil starts to break down, releasing free radicals and a substance called acrolein, the chemical that gives burnt foods their acrid flavor and aroma. Think panic, watering eyes, stinky kitchen, and bitter tasting, scorched food.
Acrolein can ruin your whole dinner but there’s another side effect of that breakdown. Yep, the heating denatures the oil. That means the heat causes the fat to degrade and lose any nutritional benefit it once had. And yes, it's also getting closer to its flash point, producing ignitable gases which can burn you and your kitchen. That said, if your oil starts to smoke, don't panic, get it off the heat fast and let it cool, it’s not likely ruined yet, but it is important to understand how the smoke point affects your food.
Traditionally, we extract oils from nuts and seeds. This is done through a mechanical crushing and pressing of the product. If packaged immediately, you've got a cold-pressed raw, or "virgin" oil, which tends to retain its natural flavor and color. But, many unrefined oils are packed with minerals, enzymes, and other compounds that don't play well with heat and tend to be especially susceptible to rancidity; these are the oils best-suited to drizzling, dressings, and lower temperature cooking.
To produce an oil with a high smoke point, manufacturers use industrial-level refinement processes like bleaching, filtering, and high-temperature heating to extract and eliminate those extraneous compounds. What you're left with is a neutral-flavored oil with a longer shelf life and a higher smoke point. Clarified butter, or ghee, follows the same basic concept: a process designed to extract more heat-sensitive components—in this case, milk solids—from a fat in order to raise its smoke point.
But not all oils are created equal. Oils that are extracted from seeds like Soybean, Cottonseed, Sunflower and a few others are significantly more harmful to your health than others. Fact is we have created new ways to extract oils which are more efficient, but exponentially more harmful to the human body. Frankly, when you look at the manufacturing process of these oils it blows the mind. The process basically involves an extremely harsh extraction process that includes deodorizing, bleaching and the addition of a toxic solvent called hexane. Once considered safe, Hexane is so neurotoxic that it can cause irritation to the mucus membranes, headaches, and nerve death.
Hexanes are used in motor fuel, shoe glues, leather products and roofing. Why we believe we can eat them too is a tribute to the craziness of man and the inability of the FDA to do their sworn duty of consumer protection. What is concerning is that these oils have made their way to all sorts of processed foods, including “healthy” salad dressings, butter replicates, mayonnaise, cookies and more.
If it were only hexane that posed the problem, then we would already be at risk, but the problems stem deeper. You see, the main problem with most of these oils is that they are high in Omega-6 polyunsaturated fatty acids.
I know, you have heard that Omega fatty acids are good for you right? But only if the ratios are maintained. You see, both Omega-3 and Omega-6 fatty acids are needed in the diet because you cannot produce them in your body. The perfect ratio is 1:1 Omega-3 to Omega- 6, and we get close to that in grass fed beef. But over the past several decades our ratio has been slowly changing. It is not unusual to find grain fed beef at a 16:1 ratio.
The problems begin when we begin to shift the Omega-6 fatty acids up. Too much Omega-6 without Omega-3 contributes to a lot of inflammation in the body. Inflammation has been determined to be the underlying factor in most of the disease states in which we encounter. Cardiovascular disease, cancer, diabetes, arthritis, the list goes on.
Of course it has traditionally been saturated fats that have received the bad rap for health. And as it turns out they are fine. Let me explain. When we refer to fats we are talking about three varieties. Saturated, monounsaturated and polyunsaturated fats. In reality if we were to break down the chemistry we are talking about the number of double bonds in the little fatty acid molecules and the saturation of the hydrogen molecule. When we look at stability of a fat we look at the number of double bonds in it. The more double bonds they have the greater is the likelihood of oxidation. Saturated fats don’t have any double bonds, so they are the most stable. Monounsaturated gain their primary descriptive from their single double bond, thus they are called “mono.” Polyunsaturated fats as you might have guessed have two or more double bonds. That makes polyunsaturated (poly=many) fats more susceptible to oxidative damage.
Two things to remember here. The longer the unsaturated fats sit the higher is their chance of rancidity, and, the more we eat and store in our body the greater the risk of oxidation. It gets more complicated but the polyunsaturated fats are more likely to go rancid, even at room temperature, so they need to be preserved more so they can last longer. Because of that we can often find some trans fats in US vegetable oils varying between .56% and 4.2%.
True, that’s a low percentage but we already understand that trans fats are bad for your health. The Polyunsaturated fats are simply more susceptible to free radical damage which turns oxidizes fat and forms peroxides. The process forces a free-radical free for all within the body damaging everything from DNA to blood vessels along its long and ugly pathway. In this way we must be far more concerned with the seed oils than other oils.
The seed oil group dramatically increases risk of death from heart disease, cancer, and many of the immune system based disease. Of course some studies do find improvement too, to be fair. But when you look at certain diseases in the population and the use of certain oils, some interesting things begin to manifest. Most important is that disease and inflammation go up with greater Omega-6 intake, and that increases the risk of disease.
Keep in mind, we are talking mostly seed oils here. These would include:
Rice Bran oil.
Also avoid all margarines and fake butters.
The list would not include fats that are more stable for cooking. These would include butter, lard, coconut oil and tallow. An interesting paradox is fish oil. And what we find is that farmed fish oil has high Omega-6 fatty acids, but wild caught fish oil is generally well balanced. Now all we need to do is consider storage. Obviously fish oil is best stored in a refrigerator, but we still cannot retard oxidation without something to stabilize the oil with. Enter krill oil. Krill oil also has astaxanthins in it, a powerful anti-oxidant which retards rancidity.
Now I bet you’re thinking right now about wok cooking right? That’s where you need to get the oil super-hot and yes, there’s a little smoke. Should we be concerned? Well that’s where we come full circle and talk about the smoke point again. Generally speaking, the higher the fat’s smoke point, the safer it is to cook with.
Now, generally speaking we always want to use a fresh oil for cooking. I realize that some people love to reuse certain oils, especially fast food, deep fry places. The only problem with this is that an oils smoke point will lower with each new smoke point. So if you are deep frying, you only have a limited number of times you can successfully reuse the oil before it oxidizes.
Most of the oils you use, such as avocado, hazelnut, sesame and walnut oils need to be kept in a refrigerator. But remember light, air and heat break it down faster so keep your oils stored in a cool, dark place, and avoid buying oil if it’s in a translucent bottle.
So what about the smoke points? Here are the smoke points of most oils, good and bad ones:
Safflower Oil 510 F or 265 C
Rice Bran Oil 490 F or 260 C
Light, Refined Olive Oil 465 F or 240 C
Soybean Oil 450 F or 230 C
Peanut Oil 450 F or 230 C
Clarified Butter 450 F or 230 C
Corn Oil 450 F or 230 C
Sunflower Oil 440 F or 225 C
Vegetable Oils 400-450 F or 205-230 C
Beef Tallow 400 F or 250 C
Canola Oil 400 F or 250 C
Grapeseed Oil 390 F or 195 C
Lard 370 F or 185 C
Avocado Oil (Virgin) 375-400 F or 190-205 C
Vegetable Shortening 360 F or 180 C
Sesame Oil 350-410 F or 175-210 C
Butter 350 F or 175 C
Coconut Oil 350 F or 175 C
Extra Virgin Olive Oil 325-375 F or 165-190 C
Walnut Oil 320 F or 160 C
Hemp Seed Oil 320 F or 160 C
All of the oils listed on this chart are refined versions; though unrefined versions of them do exist. I chose these because they are the varieties most common to a home cooking environment.
So, when cooking at high temperatures you will want to use fats with smoke points over 400 F. Remember if you are at 425 F or 450 F it’s not going to make a huge difference unless you reuse the oil.
So the question begs what oil I use for what type of cooking. That of course depends on what the oil is doing for you and the food. I cook at fairly low temperatures myself, but there’s a difference for those who want to sear, sauté or deep fry.