Are seed oils really as bad as those influencers are saying?
Observational studies seem to show no harm. Rodent studies show they cause cancer in rodents. Mechanistic studies show they break down into chemicals known to be harmful to humans. Human trials generally show a null effect, though most such studies were not designed to show a long-term carcinogenic effect.
As a chemist i’ll give my 2 cents. Is it bad? It depends. How it was extracted and how is it used. If you consume it cold pressed and you don’t cook with it - it’s fine, even healthy. If it’s refined it can be laden with residual organic solvents. Also MUFA’s and especially PUFA’s have poor thermal stability, that’s where the problems start. High temperature opens up these weak pi bonds in double bonded carbon sections facilitating synthesis of random compounds and polymers, that can cause cancer and inflamation. Saturated fat on the other hand is thermally stable @ cooking conditions.
From what I’ve gathered, the evidence seems to be conflicting.
My takeaway from that is that I’ll avoid them until strongly demonstrated otherwise. I think “avoid” as the default makes sense for something so novel to human diets.
Don’t get me wrong – I’ll still go out to eat and get exposed to them, but I won’t use them at home.
And, of course, maybe they are okay! But the evidence doesn’t seem strong enough so far, in my evaluation. Science doesn’t just always have the answers. It takes a while to get there.
I’m biased as I would say they are bad, but I’ll take a more measured “fair” approach.
There are claims and science studies that point to how seed oils can improve LDL Cholesterol, and lower heart disease risk. However, I’d say the issue with seed oils is that they’re highly refined and processed, they’re cheap to produce and our consumption has drastically increased since the 1990s. This seems to correlate with America’s Obesity problems getting worse ever since then, even if the seed oils themselves may or may not be the cause.
Perhaps I’m conveniently misinterpreting a quote I read from Harvard’s Guy Crosby, but I find this defense interesting as a low-carb advocate myself:
“While it’s true that many foods that use seed oils—such as packaged snacks and french fries—are unhealthy, they also tend to be high in refined carbohydrates, sodium, and sugar. “Sure, if you cut back on these foods, chances are you’re going to feel better,” Crosby said. But these other components, not the seed oils themselves, are the culprit behind weight gain and other negative health outcomes.”
Link to this quote here:
If the issue is the carbohydrates, sodium and sugar in these foods and we know those things are bad, why are seed oils preferable to butter, pork or beef fat? Assuming that it’s not the type of fat that is necessarily leading to negative health outcomes? My guess is that it largely comes back to money. It’s simply cheaper to fry french fries in Canola oil than it is to fry them in Beef Tallow.
Anecdotally speaking, what you will also find is if you focus on eating a single ingredients, whole foods style diet, much of your exposure to seed oils is significantly reduced. It mainly becomes a matter of swapping Canola Oil for Olive Oil, Butter or Ghee for cooking, and you casn either making Salad Dressings and other toppings yourself, or purchase versions from the store that don’t contain these oils.
The science says seed oils are between no worse and slightly better than most oils (olive is a clear standout in general as being very healthy), and in particular are much better than animal fats.
There have been studies showing seed oils do bad things in very high doses in mice, and polyunsaturated fats do degrade in ways other fats don’t - But oils have antioxidants that tend to prevent that degradation as long as you don’t overheat the oil, reheat it, or keep it hot for hours on end.
In humans, the mechanistic theories influencers lean on to say seed oils are harmful just don’t pan out. The human body is a very complex system, and what an oil does if you put it in a petri dish is not what it’ll do in a human body. We have ways to repair oxidant damage, fatty acids get broken down or burnt for energy, inflammation is a lot more complicated than “on/off” or even than “bad/good”.
In the abscence of those theories, and the well-established fact that saturated animal fats are bad for the heart, the most reasonable conclusion is that seed oils are superior to animal fats for health, and there’s currently no reason to think they’re worse than non-seed plant oils.
I’m unconvinced about them. Speculating about a mechanism by which they could be harmful is a great deal different than demonstrating that harm actually occurs in humans, which so far nobody has done.
Seed oils causing cancer in mice also does not convince me because diet studies in mice are notoriously difficult to replicate the results of in humans. Mice have entirely different fat and dietary needs and overloading them on fat from seeds probably isn’t good for them.
RCTs have been short term but don’t show any negative effects from consuming them.
Population studies are difficult to extrapolate from because populations consuming a ton of seed oils are also probably consuming a ton of highly processed foods. The real trick is to try to disentangle seed oils from other very unhealthy components of diet.
I don’t consume them (except pretty occasional peanut oil on the 4 times a year I deep fry anything), because I like olive and avocado oil so I don’t have much of a dog in the race. If I were poorer though I wouldn’t be super concerned about using small amounts of canola or similar to saute foods with, as I am similarly unconvinced that deep frying some tofu a couple times a year in peanut oil is the thing that’s going to do me in.
There is an argument for caution here because it’s a big unknown but I’m just not that concerned personally.
The seed oil controversy rages almost exclusively online. You get the odd narrative review criticising them or trying to exonerate saturated fat but there’s a very good reason why every last dietary and health body advises PUFA heavy oils over SFAs.
If you prefer video format I’d suggest Nutrition Made Simple on YouTube.
There’s typically a script involved with the anti seed oil cohort. Things like:
There’s more but that’s what I remember off the top of my head. The science is clear, really clear. Every health institution and government body comes to the same conclusion. Why? Because the science is clear. I’ll reply to my own comment covering different areas concerning seed oils.
Edit: Ok I can only reply once so I’ll limit how much I write, here’s a paper on canola oil:
Be cautious of anyone who says they are harmful. They may be, but the evidence that shows it just isn’t there, so we don’t really know. Anyone who says otherwise is full of it.
However, what doesn’t need scientific evidence to back it up, is that seed oils are a very low nutrient density food. Lots of calories for not a lot of nutrition. Seed oils give you some Vitamin E, and Omegas, but if you are wanting to consume more of those, there are much better sources for them.
About 2 years ago, I eliminated all seed oils from my diet. When I started doing that, I was shocked to find out that I was eating about 350 calories per day just from oils, because they are hidden in sooooo many foods these days.
Yea the data is still super conflicting. Studies done in mice don’t always transfer to humans well so those don’t mean much. A lot of the studies that show no harm or null effects are questionable at best. I haven’t seen a ton of long term research which is really where this kind of thing matters.
For now, I’ll avoid them. I think foods that have a lot of seed oils in general aren’t the healthiest in the first place… if I’m cooking I’ll use olive or avocado just purely from a taste standpoint.
I don’t think you HAVE to avoid them. But given historical trend, the causation with chronic disease is not impossible.
In short, the jury is still out on their long term affects. I choose to avoid them purely due to the foods that DO contain a ton of seed oils are unhealthy for other reasons as well.
Excess adiposity is the biggest issue. Seed oils aren’t bad if you aren’t over consuming fat. Saturated fats aren’t bad if you aren’t over consuming fat. Storing excess adipose tissue can lead to metabolic issues. There is nuance to the affects of different fatty acids and it can get more complicated than that but it doesn’t need to
Cut them out for one month and see how you feel. Any food that has seed oil in it you can usually get without seed oils. You’ll never get an honest answer to this question and you’ll have to find out for yourself. Anecdotally, I cut them out and I’m so pleased I’m never going back!
Of course it’s not as bad as influencers are saying. Think about what an influencer is - supposedly they’re supposed to influence you to do something (as in, do something with your wallet).
You don’t have to go to college to be an influencer. You don’t even need to graduate high school to be an influencer - much less have a masters, a medical degree, or any kind of licensure at all, whatsoever.
If influencers are saying something that you’re not hearing much of from the scientific community, you can ignore it
Seed oils are fine. They are just foods. Just don’t consume it in excess
No.
Flaxseed oil contains a better omega 6:omega 3 ratio then any land based source at 0.3:1. Canola oil (most popular US home cooking oil) beats all land animal sources that are not dairy (so better then beef, pork etc) at 2.2:1. Soybean oil (most popular US commercial cooking oil) has about the same ratio as pork fat at 7.5:1, still beats eggs and poultry. All three of those also beat olive oil at 13.2:1. People who are genuinely concerned about their omega ratio will be substituting their lard & tallow for canola.
While lower ratios are common in diets with proven longevity benefits its not clear what role the ratio plays, they are also very low in things like red meat and have plenty of carbs. Actual evidence of health benefits of a 4:1 diet only show up in those already diagnosed with an inflammatory disease like RA.
Our dietary needs are ~10 times more Omega 6 then Omega 3, if you want to improve your ratio you should eat more omega 3’s rather than decrease your 6’s as LA (omega 6) is an essential nutrient.
The big concern with high consumption of LA is that your body is terrible at synthesizing DHA & EPA (omega 3’s) and the enzymes used in this synthesis are shared with omega 6 so there is a competition concern. The solution to this is to eat or supplement with DHA & EPA (oily fish). There are no land based sources for DHA & EPA.
I am extremely unconvinced with the hexane argument (the solvent used to extract seed oils) as the amount that actually remains in seed oils that someone would reasonably ingest in a day is orders of magnitude lower then that we ingest through the air every day because gasoline engines exist.
I am not very convinced about the oxidation argument because rancid oil has a very distinct taste & smell. I don’t think people will actually use oils if they smell like rotting eggs.
We should rephrase the question to: “Why are so many people suffering with degenerative diseases such as Alzheimer’s, heart disease, cancer, diabetes, asthma, arthritis, and obesity?”
If you look at people with a lot of health problems and what they eat, they usually eat lots of processed foods, fast food, fried foods, and refined carbs. Those processed foods often contain Industrial Seed Oils which contributes to the destructive free radical oxidation.
Let me clarify, Coconut Oil, Olive Oil, Avocado Oil, Almond Oil, and Palm Oil are healthy fats because there is minimal processing after being pressed.
It’s the Canola Oil, Corn oil, cotton seed oil, grapeseed oil, peanut oil, Safflower oil, soybean oil, sunflower oil that are toxic. When they are pressed from the seed, they come out dark and foul-smelling. A lot of industrial processing is required to purify the oils, which adds to the toxicity. And we know pretty well that highly processed foods are making us sick.