I grew up in a foodie household, and my mom always used Mazola vegetable oil to cook with. At the time (the 70s and 80s, if you must know), there wasn’t a huge variety of oils in the supermarket, and nobody really cared about nutrition all that much. People were more like, ‘pass the cheez crackers and Tab!’
Now, we’re all concerned with our health and the number of different oils in the grocery store is dizzying. Add in certain diets that say that saturated fat is healthy, and the whole fats thing is even more puzzling. Is saturated fat okay now? Is olive oil dangerous? Is canola oil ‘toxic’? How about all seed oils? Should we believe the ‘seed oils are inflammatory’ rhetoric we’re seeing everywhere?
Just a little primer on fats
Monounsaturated: These fats are known as the ‘good’ fats because they appear to help improve blood cholesterol levels. Oils high in monounsaturates include olive, canola, and avocado. Nut oils like walnut and hazelnut are great too, but their smoke points are super low so use these oils in salads and cold dishes.
Polyunsaturated: These include omega-3 and omega-6 fats. Diets that have a lot of omega 6 and too little omega 3 fats are still thought by some people to be inflammatory, although current research does NOT support this theory.
The confounder for this may be that many of the high omega-6 oils we eat are found in ultra-processed foods, which do appear to be inflammatory. If someone is eating the Standard American Diet, it’s impossible to tease out whether it’s the omega-6 fats they’re consuming that are causing them issues, versus their refined grains, sugar, and low fibre/fruit/vegetable diet.
Oils high in polyunsaturates include canola, soybean, corn, and sunflower.
Saturated: The degree of unhealthiness of saturated fat is perhaps the most debated nutrition topic of this century. The majority of available human research (and here) (and here) (and here) (and here) suggests that replacing saturated fat with polyunsaturates (but not refined carbs) can lower cholesterol levels significantly (and some doesn’t).
There appears to be a correlation between a diet high in saturated fat and high cholesterol/heart disease, but because of the way nutrition research is conducted (ie, you can’t keep people in a lab and feed them a controlled diet for years), nobody has ever singled out saturated fat itself as the exact cause in this case. Oils high in saturated fat include coconut and palm oil.
Still, we do advise against consuming large amounts of saturated fat because we do suspect that it causes heart disease.
A lot of people ask me about coconut oil. It’s not the nutrition miracle some people will have you believe, and it is high in saturated fat. This explainer on coconut oil is fantastic, but TL;DR: Don’t eat it by the spoonful. Don’t eat any oil by the spoonful, and you should be just fine.
It’s important to note that every single oil is a combination of these fats. Even the most saturated fats in the world – coconut and palm kernel oil, FYI – contain at least some unsaturated fat. By the same token, even olive oil contains saturated fat.
It’s also important to consider that different people react differently to different nutrients. Just because your boss can eat nothing but steak for three months and have their cholesterol levels drop, doesn’t mean that you’re going to have the same outcome. Our genetic makeup, gut bacteria, and possibly other factors influence how our bodies process food. This is why I become infuriated when people try to say that their diet is the ‘best’…it’s just never going to be true for everyone.
One-size-fits-all doesn’t work in nutrition (that’s another blog post all together).
Let’s talk about smoke points, because many people have asked me if oils become harmful when they’re overheated. When an oil breaks down under heat, it produces polar compounds, which can be bad for our health. If you’re cooking with an oil, choose one with a higher smoke point (depending on how high you’re heating it and for how long).
This guy wants us to believe that heating our seed oils makes them toxic (and of course, that we should never eat seed oils for various other reasons):
I’ve pulled this ah-mazing chart from Diet vs Disease on smoke points and polar compounds because I couldn’t possibly improve on it.
It’s important to note that the study that this chart is pulled from was sponsored by the olive oil people. Also, the oils in the study were heated to temps that home cooks would rarely if ever reach. This is an important point.
Notice that canola oil, sunflower oil, and grapeseed oils, as the graphic says, have the highest smoke points but also the highest percentage of polar compounds. The lesson: don’t overheat your oils. Again, the oils in this chart were heated for far longer times, and at higher temperatures that anyone would use during home cooking.
seed oils: are they harmful?
I thought that by 2022, we could stop talking about seed oils, but here we are.
It’s not surprising that seed oils are still enemy #1, with all of the social media content being created to make you fear them. I’m going to assume that 99% of the people whose anti-seed oil content you see, have no clue what they’re talking about (or have something to sell).
Are seed oils industrial?
The mere mention of ‘industrial oils’ connotes visions of your potato chips being made with some sort of inedible engine oil from a big drum.
The refined oils we eat in food aren’t ‘industrial,’ they’re food-grade and safe. Nobody is going to a gas station to get the oil that they’re cooking your food in.
When you search ‘refined oils harmful’, all sorts of quacky sites pop up. It’s safe to say that when I see Mark Hyman, Food Babe, or some shirtless doctor telling people not to do something, I most certainly will recommend doing the opposite. Predictably, they and many other ‘alternative’ sites recommend staying far away from refined oils.
Refined oils like canola, soy, corn, and palm are expelled from their sources using chemicals or a mill. The heat used during processing may decrease antioxidant and vitamin content somewhat, but is not high enough to cause oxidation (sorry, Dr. Pedi-not-a-doctor). If someone is saying that there are toxic chemicals in seed oils from processed – usually hexane, just know that after processing, there is no hexane left in the oils.
Do seed oils cause inflammation?
This is a commonly-used claim – apparently, seed oils are inflammatory and are responsible for EVERYTHING BAD THAT EVER HAPPENED TO US!
Just an aside that if you see claims that X ingredient is responsible for Y exhaustive list of horrible things that happen to our health (besides seed oils, sugar is often the subject of these claims), this is a red flag. Actual scientists and people who understand science and research and physiology do not make these claims, because they’re simplistic and extremely illogical.
Just like with seed oils, human health is complex. Blaming one single ingredient for the majority of society’s ills is ridiculous and misleading.
Back to seed oils and inflammation, current research refutes this claim wholeheartedly. You’ll see many people using animal studies to ‘prove’ that seed oils are inflammatory or just overall horrible for us, but remember that animal studies can not be extrapolated to humans in this way. Sure, preclinical research (aka animal and cell studies) is very important. But taking a rodent study and using it for recommendations in humans is what people do when they have an agenda without human research to support it.
Let’s look at the research around seed oils and inflammation, shall we? As in, the newer, human research:
Here’s a 2018 study that shows that in healthy adults, omega-6s do not raise inflammatory markers.
Just to provide some context to the above rant, here’s a study showing how mice and humans react differently to omega fats, and why we can’t (or shouldn’t) use rodent studies to prove things. The study also supports the evidence that omega-6s are not inflammatory.
And this 2021 meta analysis of 83 studies that looked at 41,371 people who have IBD and other inflammatory diseases like Crohn’s and colitis showed that omega-6 fats have no effect on inflammatory markers.
The seed oil and inflammation narrative has been blown really far out of control, thanks to this guy and people like him:
Seed oils, in short.
I don’t think there’s any one food in the world that you need to avoid altogether. With oils, it comes down to how much and how often you choose them. Let’s put it this way: if you’re eating a ton of ultra-processed foods, this is a whole other issue. If you’re cooking with only refined oil, mix it up with other oils. Variety is one of the hallmarks of a healthy diet.
There’s no reason to get paranoid because people are posting about the dangers of seed oils and how toxic they are. If you’re eating a lot of ultra-processed foods that happen to contain seed oils, your overall diet could probably use a few tweaks.
the bottom line on Seed oils.
Nobody eats just oil, they eat food with oil in it. Just like with everything else we consume, it’s always best to mix things up. Don’t eat one type of fat – as I mentioned earlier, every oil/fat has a different fatty acid profile. Eating varied types helps us get different fatty acids that are essential for health.
Cut back on ultra-processed foods. Eat more whole and minimally processed ones.
Monounsaturated fats seem to have the most positive evidence for health, with unsaturated oils coming in at a close second.
Trans fats are the only fat we know is 1000% unhealthy. Nobody’s arguing about that one. They’re being taken out of the food supply, but again: if you’re eating a lot of trans fats, chances are you’re eating a highly processed diet.
Enjoy your food, and as with anything, use a combination of different oils. Stop listening to people who don’t wear shirts and call themselves ‘doctor.’ Scroll by fearmongering garbage content that’s meant to scare you into not eating certain foods.