Why Are Seed And Vegetable Oils Bad For You? The Shocking Truth

Why Are Seed And Vegetable Oils Bad For You?Modern nutrition has got it all wrong.

Often, your best bet would be to listen to what the nutrition authorites have to say…

…then do the exact opposite.

They tell you to eat a high-carb, low-fat diet… but you eat a low-carb, high-fat diet and your health improves.

They tell you to reduce animal foods, you eat even more of them and feel better than ever.

It applies to carbs, saturated fat, animal foods, eggs, butter and a thousand other things in mainstream nutrition.

This rule (I like to call it “Kris’s Law”) states…

Kris’s Law

Listen carefully to what the nutrition authorities have to say, then do the exact opposite for best results.

There are some exceptions… paradoxes if you will… but this rule tends to be correct 80% of the time.

This rule also applies to the industrial oils, which are the topic of this article.

For some reason, they haven’t merely been acknowledged as suitable for human consumption, but downright healthy, by our beloved authorities.

These oils are usually called “vegetable oils”, “seed oils”, or if you want to sound fancy… polyunsaturated fats.

Seed and Vegetable Oils – What Are They?

The Most Common Types:

  • Soybean Oil
  • Cottonseed Oil
  • Grapeseed Oil
  • Sunflower Oil
  • Safflower Oil
  • Canola Oil
  • Corn Oil

You will find these in various processed foods, “health” foods, vegetarian products and commercial cooking oils and dressings.

The way they are made isn’t very appetizing.

Basically, the raw materials are the various plant seeds. Somehow they manage to extract the tiny amounts of oils from these seeds and collect it into containers, then sell it to humans.

The processing method is rather disgusting and involves solvents, the most common being the toxic petroleum solvent Hexane (1).

Sometimes, the oils are processed even further and turned into partially hydrogenated fats, otherwise known as trans fats, but that is a different story altogether.

The main reason these oils are unhealthy, is that they are composed primarily of polyunsaturated Omega-6 fatty acids.

This doesn’t apply to healthy plant fats like olive oil and coconut oil, which are mainly monounsaturated and saturated, respectively, and don’t require the harsh chemical processing methods.

Increased Consumption

These oils are relatively new to the human diet, which makes sense since we weren’t able to produce them until fairly recently on an evolutionary scale.

They weren’t available until a hundred years ago, which is way too short of a time for genetic adaptation.

Here is a graph that shows how much consumption has increased in the past 100 years (source):

Polyunsaturated Fat Consumption in the USA

The increase in consumption has lead to a direct increase in the polyunsaturated fat content of our body fat stores (source):

Increase in Linoleic Acid in Body Fat Stores

What this means, is that the increased consumption of these oils has actually lead to physical changes in our bodies. We have replaced saturated/monounsaturated fats with polyunsaturated fats in our body fat stores.

The consequences of this aren’t fully known at this point.

Polyunsaturated Fats: Omega-3 vs. Omega-6

There are two types of polyunsaturated fats that we are concerned with, Omega-3 and Omega-6.

The difference between Omega-3 and Omega-6 has to do with the placement of the double bond in the molecule.

We’ve all heard of Omega-3 before. It’s the one we find in fish and grass-fed meat, and can improve various biomarkers of health such as cholesterol, triglycerides and blood pressure.

However, Omega-6 is not the same. It is “essential” like Omega-3, meaning that we need to get some amount of it from our diet or we get sick, but Omega-6 and Omega-3 have different effects in the body and we need to get them in a certain balance.

Getting too little, or too much, of either one is likely to be harmful. It turns out that we’re getting too little Omega-3, and way too much of Omega-6 (mostly from the oils) in the modern diet.

Why Are Seed And Vegetable Oils Bad For You?

The balance of polyunsaturated fats is supposed to be somewhere from 1:1 to 3:1 (typical for our hunter-gatherer ancestors), meaning that for each molecule of Omega-3 we should get 1 to 3 molecules of Omega-6. The balance in the modern diet is way off, somewhere between 10:1 and 30:1.

This is believed to have dire consequences for the human body.

The polyunsaturated fats are used as raw materials to create signaling molecules called eicosanoids. These molecules mediate inflammation, immunity, cellular messaging and various other processes.

When the Omega-6:Omega-3 balance is off, these important pathways start to malfunction.

The biggest sources of Omega-6 fatty acids in the diet are the seed and vegetable oils we’re talking about here.

Polyunsaturated Fats are More Prone to Oxidation

Because polyunsaturated fats have many double bonds (poly = many) in the molecule, they are more prone to a process known as lipid peroxidation.

When this happens, free radicals steal electrons from the fatty acid molecule and cause a “free radical chain reaction”, where the damage propagates until stopped.

Polyunsaturated fats are much more likely to become spontaneously oxidized than their saturated and monounsaturated counterparts.

Increased oxidation can lead to all sorts of things, including heart disease, cancer and skin ageing.

To sum up, the biological reasons that excess Omega-6 fats (from seed and vegetable oils) are bad for you are these:

Excess Omega-6 fats in the diets distort the balance between Omega-6 and Omega-3 fatty acids, leading to malfunctions in important signaling mechanisms. They are also prone to oxidation, potentially causing damage to vital molecules in the body.

Polyunsaturated Fats and Disease

You have probably heard at some point that polyunsaturated fats are good for your heart. It’s true.

But as with many things in nutrition, the full story is more complicated.

The two types of polyunsaturated fats, Omega-3 and Omega-6, have different functions in the body like I mentioned above.

Increasing Omega-3 intake is extremely healthy and this is well known. Me and the dietitians agree on this, one of the paradoxes of Kris’s law.

Making the distinction between Omega-3 (from fish oil, fish, grass-fed animals) and Omega-6 (from processed seed and vegetable oils) is paramount.

Most of the studies concluding that polyunsaturated fats decrease heart disease risk look at Omega-3 and Omega-6 combined. When you look at Omega-6 specifically then the story looks completely different.

Increasing Omega-6 intake is actually bad for your heart (2), which makes sense given their pro-inflammatory and pro-oxidative effects.

Another study found that replacing saturated fat with polyunsaturated fat lead to an increase in oxidized LDL cholesterol (3), the stuff that likes to lodge in your arteries and give you heart disease (the #1 killer).

There are still some studies showing that omega-6 fats are protective against heart disease, so you should take all this with a grain of salt.

A study of 11.699 Swedish post menopausal women discovered that a dietary pattern high in polyunsaturated Omega-6 fats was associated with an increased risk of breast cancer (4), the most common cancer in women.


Despite the plausible biological mechanism, evidence linking polyunsaturated Omega-6 fats to disease in humans is scarce.

Therefore, I can not make a firm recommendation based on strict evidence, but I can give you my personal opinion based on a clear cut biological mechanism.

Given that these oils are relatively new to the human diet, and that basic biochemistry predicts that they may cause pro-inflammatory and pro-oxidative effects, I personally believe that these oils should be avoided at all costs.

The added fact that they’re leading to actual physical changes in our bodies, coinciding with the period where the diseases of civilization become more common, rings even more alarms in my head.

I feel certain that with time, the damaging effects of these fats will start to show more clearly.

These oils aren’t real food. They are void of nutrients, made in factories with harsh chemical processing methods and have no place in a real food based diet.

I prefer to eat coconut oil, olive oil, a bit of nuts and plenty of animal fats.

I honestly believe this is the best way to ensure optimal health.

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  1. Your stupid add tweet thing does not have a close button, and is preventing reading of your blog.

    • Kristjan says:

      You mean the tweet button? If I click it, it opens up with a new window which is close-able.

      • The window is closable but the original window/pop up/whatever you call it remains after closing the window. Windows 7/chrome.

        It is also like this of wife’s computer. It makes your blog unreadable.

        • Kristjan says:

          Are you referring to the message that pops up on the bottom right?

          • Nothing is popping up on mine….just read the (very interesting!) blog with no problem!

          • I think the poster means the twitter, Facebook etc widget that scrolls at the top of the screen along the left hand side. It sits over the text in places. It disappears eventually but I can see it might block the view in some browsers.

          • Kristjan says:

            I just changed to a new social sharing plugin. Thanks for letting me know.

  2. Chris P. says:

    Are there any alternatives we can use for cooking food, if canola and vegitable oils shouldn’t be use? Olive and coconut? I greatly appreciate the info, but also want to make sure I have sone solutions if given a problem by someone. :p maybe you know of some.

  3. Funny to see that it turns out saturated fats are what’s good for you, and vegetable oils are rather on the negative side.

    Another thing to consider: human body fat, the fat that the body uses for energy and stores for a rainy day, is saturated fat.


    • I second Marks point and it’s also worth adding that the preferred method of fat energy transport in the body is also saturated.

      I’ve been on to friends and clients for years about getting all seed and veg oils (in a processed state, not from nuts and fresh veg) out of their diets for years. I’ve yet to see anyone who doesn’t benefit from doing this.

      Keep up the good work, people need to know this stuff!


  4. Good post. I have taken out of my diet most of these oils but probably have to look better at the ingredients of the things I buy in the supermarket. I use coconut oil, olive oil and clean butter. But what about flaxseed oil?, I take in about 1 tablespoon everyday should I stop that?

  5. Animal Fats from pasture raised animals is the key!

  6. Great post Kris, thanks for the tips.

    And I have no trouble reading your blog with your popup ;)

  7. I’ve heard from low carbers before not to use veggie oils and now I know why! Thanks for the info in this post. I used to use canola and safflower oil all the time, now I use olive oil pretty much exclusively.

  8. Janelle says:

    I use coconut oil for cooking because I’ve heard that olive oil will also oxidize at high temps. I’m pretty sure that healthy omega-3’s are monounsaturates as opposed to polyunsaturates, too. Am I wrong?

    • Yes you are wrong, omega 3’s are highly polyunsaturated, but that doesn’t have to be a problem;

      It’s only when polyunsaturated fats hang around in the body for too long that they become a problem. And under what conditions does that happen? (because understanding this is key)

      When you eat a diet that’s high carb, especially processed carb and high in n6 PUFA’s. That way you experience an energy surplus (so your body doesn’t need to use the PUFA’s for energy) and they get to wait until they can be dealt with (because you don’t actually need more than about 1g a day of them, any more is too much). They hang around in an oxygen rich environment (your blood) and become oxidised.

      I learned about the dangers of PUFA’s years ago from one of my nutrition teachers, who in turn studied extensively under Ray Peat (raypeat.com), I then went and read his stuff, applied what he was teaching, and noticed a difference.

      Hope this helps,

  9. Elisabeth says:

    Hi, I haven’t seen a reference to sesame or peanut oil?

  10. Hi. Great article. I heard from my trainer and biology teacher saying that when heated up olive oil turns into trans fat. I’m allergic to coconut, what are some other oil alternatives ?

  11. Thanks again Kris!

  12. Roger jackson says:

    Enjoyed your article about oils. Just thought I’d add this for info and food for thought. You can take the oil, be it corn sunflower or canola or whatever and with the addition of lye etc you can turn it into diesel fuel. People collect the old oil from restaurants etc to make their own fuel, so putting it into our bodies has to be a mistake. I haven’t heard of olive oil or coconut oil or lard or butter being used this way. Just a thought.

  13. Kris,

    You’ve got it exactly right. I’ve studied this for years and agree with you 100%. I’m an RN and almost everything they taught me in college was flat out wrong. Keep up the good work. The “Bible” on fats & oils (lipids) is “Know Your Fats by: Mary G. Enig”.

  14. What about products like Spectrum Refined Organic Canola Oil?

    According to the website, this is the info on it:

    This oil has a medium- high (Up To 425°F) ‘smoke point’ making it ideal for sautéing at medium- high heat or, because of its neutral flavor, for baking.

    100% mechanically (expeller) pressed naturally refined organic canola oil.

    Thanks! Suzanne

  15. Halli Magg says:

    Here we can see the smoking point of various oils.
    coconut oil and olive oil have similar smoking point (i.e. heat tolerance).

    Here is a recipe for a good cooking oil from the oil expert Mary G. Enig from her book Know your fats.

    1 part olive oil, 1 part sesame seed oil, 1 part coconut oil. Mix together and keep in a dark bottle and keep it closed in a dark place.

    This one is very good. Enjoy

  16. What about clarified butter?

  17. Shedevr says:

    What about avocado oil?

  18. Thank you for your inspiration. Our world is so bad.The information that they send out there is so out of balance. You can take a study and make it say whatever you want to to prove a point. There is so much confusion out there. I agree with take what they are saying and do the total opposite. I usually do not listen, but I have seen those who do. I have freinds and they are going crazy trying to be “healthy”

    I am taking a natural approach to life nowdays. I try to eat food in it’s natural forms. I see the health problems of those all around me, I see their bad diets. I am living healthy now. It is amazing how I can taste such a difference now. I can taste the chemicals in foods. Food that I used to love, now taste so disqusting and chemical like. I love he clean clear taste of “real food” I am on a long journey of gaining my health back, but I am on the right road thanks to people like you who tell us like it really is.

  19. What about groundnut or peanut oil? I have been using this for ages. Should I change to just butter and olive oil?

  20. Thank you for the info!

    It’s so confusing out there with all the info we are hammered with, it is quite overwhelming at times. Thank you for the clarifications.

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