6 Reasons Why Vegetable Oils Are Toxic

Unhappy and Frustrated DoctorMany people perceive vegetable oils as healthy.

Maybe it’s because they have the word “vegetable” in them.

I mean… vegetables are good for you, right? So vegetable oil must be too…

Even the mainstream nutrition organizations recommend that we eat them, because according to them, unsaturated fats are much healthier than saturated fats.

However, many studies have now demonstrated that these oils can cause serious harm (1).

The composition of the fatty acids in them is different than anything we were ever exposed to throughout evolution.

This is leading to physiological changes within our bodies and contributing to multiple diseases.

Here are 6 reasons why vegetable oils are downright toxic.

1. Vegetable Oils are Very “Unnatural” in Large Amounts

Vegetable Oils

In this article, I’m referring to processed seed oils like soybean oil, sunflower oil, corn oil, canola oil, cottonseed oil, safflower oil and a few others.

Even though they aren’t really vegetables, these oils are commonly referred to as “vegetable oils.”

These oils contain very large amounts of biologically active fats called Omega-6 polyunsaturated fatty acids, which are harmful in excess.

This does NOT apply to healthy plant oils like olive oil or coconut oil, which are extremely good for you.

Humans have been evolving for a very long time, but industrial food processing is brand new. We didn’t start producing vegetable oils until about a hundred years ago.

Between the years 1909 and 1999, the consumption of soybean oil increased more than a thousandfold and now supplies about 7% of calories in the U.S. diet (2).

Take a look at this video to see how commercial canola oil is made:

This processing method is really disgusting and involves pressing, heating, various industrial chemicals and highly toxic solvents. Other vegetable oils are processed in a similar manner.

It baffles me that anyone would think this stuff is fit for human consumption.

If you choose healthier brands that have been cold pressed (lower yield and therefore more expensive) then the processing method will be much less disgusting, but there is still the problem of excess Omega-6 fats.

Bottom Line: Humans were never exposed to these oils until very recently on an evolutionary scale, because we didn’t have the technology to process them.

2. Vegetable Oils Mess up The Fatty Acid Composition of The Body’s Cells

Rapeseed Oil

There are two types of fatty acids that are termed “essential” – because the body can’t produce them.

These are the Omega-3 and Omega-6 fatty acids.

It is absolutely essential for the human body to get these fatty acids from the diet, but it must get them in a certain balance.

While humans were evolving, our Omega-6:Omega-3 ratio may have been around 4:1 to 1:2. Today, our ratio is as high as 16:1 on average, with great variation between individuals (3).

These fatty acids aren’t just inert structural molecules or fuel for the cell’s mitochondria, they serve vital functions related to processes known to affect various systems like the immune system (4).

When the balance of Omega-6s and Omega-3s in the cell is off, things can start to go terribly wrong.

Another problem is the relative unsaturation of these fatty acids. Polyunsaturated fats have two or more double bounds, while monounsaturated fats have one and saturated fats have no double bonds.

The more double bonds in a fatty acid, the more reactive it is. Polyunsaturated fats tend to react with oxygen, which can cause chain reactions, damaging other structures and perhaps even vital structures like DNA (5, 6).

These fatty acids tend to sit in the cell membranes, increasing harmful oxidative chain reactions.

According to this graph, our body fat stores of Linoleic Acid (the most common Omega-6 fat) have increased 3-fold in the past 50 years.

Linoleic Acid in Human Body Fat

Photo from: Stephan Guyenet.

That’s right, excessive consumption of vegetable oils leads to actual structural changes within our fat stores and our cell membranes.

I don’t know about you, but I find that to be a pretty scary thought.

Bottom Line: Omega-6 and Omega-3 fatty acids are biologically active and humans need to eat them in a certain balance to function optimally. Excess Omega-6s in our cell membranes are prone to harmful chain reactions.

3. Vegetable Oils Contribute to Inflammation

Bottles of Vegetable Oil

Omega-3 and Omega-6 fatty acids are used to make substances called eicosanoids in the body.

These are modified fatty acids that sit in the cell membranes.

There, they play a crucial role in bodily functions like cellular messaging, immunity and inflammation.

If you’ve ever taken aspirin or ibuprofen and noticed relief from headache or some kind of pain, then that’s because these drugs inhibit the eicosanoid pathways and reduce inflammation.

Whereas acute inflammation is good and helps your body heal from damage (such as when you step on a lego), having chronic, systemic inflammation all over your body is very bad.

Generally speaking, eicosanoids made from Omega-6s are pro-inflammatory, while those made from Omega-3s are anti-inflammatory (7).

These different fatty acids compete with each other. The more Omega-6 you have, the more Omega-3 you need. The less Omega-6 you have, the less Omega-3 you need (8).

Having high Omega-6 AND low Omega-3 is a recipe for disaster, but this is the case for people eating a Western diet.

Put simply, a diet that is high in Omega-6 but low in Omega-3 contributes to inflammation. A diet that has balanced amounts of both Omega-6 and Omega-3 reduces inflammation (9).

It is now believed that increased inflammation can contribute to various serious diseases, including cardiovascular disease, arthritis, depression and even cancer.

Bottom Line: Eicosanoids, signaling molecules made from Omega-6 and Omega-3 fats, are crucial in regulating inflammation in the body. The more Omega-6s you eat, the more systemic inflammation you will have.

4. Vegetable Oils Are Loaded With Trans Fats

Bottle of Soybean Oil

Trans fats are unsaturated fats that are modified to be solid at room temperature.

These fats are highly toxic and are associated with an increased risk of various diseases, like heart disease, cancer, diabetes and obesity (10, 11, 12).

They are so bad that even the governments around the world have started taking action, setting laws that command food manufacturers to reduce the trans fat content of their foods.

However, a little known fact is that vegetable oils often contain massive amounts of trans fats.

In one study that looked at soybean and canola oils found on store shelves in the U.S., about 0.56% to 4.2% of the fatty acids in them were toxic trans fats (13).

If you want to reduce your exposure to trans fats (you should) then it’s not enough to avoid common trans fat sources like cookies and processed baked goods, you also need to avoid vegetable oils.

Bottom Line: Trans fats are highly toxic and associated with multiple diseases. Soybean and canola oils commonly sold in the U.S. contain very large amounts of trans fats.

5. Vegetable Oils Can Dramatically Raise Your Risk of Cardiovascular Disease

Old Man Taking Pills

Cardiovascular disease is the most common cause of death in the world (14).

Whereas saturated fats were once considered to be key players, newer studies prove that they are harmless (15, 16).

Now the attention is increasingly being turned to vegetable oils.

Multiple randomized controlled trials have examined the effects that vegetable oils can have on cardiovascular disease.

3 studies have found a drastically increased risk (17, 18, 19), while 4 found no statistically significant effect (20, 21, 22, 23).

Only one study found a protective effect, but this study had a number of flaws (24).

If you look at observational studies, you find a very strong correlation.

This graph is from one study where the Omega-6 content of blood was plotted against the risk of death from cardiovascular disease (25):

Mortality And Omega-6 Fat Consumption Graph

You can see the U.S. sitting there at the top right, with the most Omega-6 AND the greatest risk of death from cardiovascular disease.

Even though this study only shows a correlation, it makes perfect sense given that inflammation is a known contributor to these diseases.

I’d like to point out that there are some studies showing that polyunsaturated fats reduce the risk of cardiovascular disease. But the problem is that they don’t make the distinction between Omega-3s and Omega-6s, which is absolutely crucial.

When they do, they see that Omega-6s actually increase the risk, while Omega-3s have a protective effect (26).

Bottom Line: There is evidence from both randomized controlled trials and observational studies that vegetable oils can increase the risk of cardiovascular disease.

6. Vegetable Oil Consumption is Associated With Various Other Diseases

Bottle of Sunflower Oil

Because polyunsaturated fats are so tightly involved in the function of the body on a molecular level, it makes sense that they could affect other diseases as well.

Many of these association aren’t well studied in humans (yet), but there are both observational studies and animal studies linking vegetable oils to other serious diseases:

  • In one study, increased Omega-6 in breast milk was associated with asthma and eczema in young children (27).
  • Studies in both animals and humans have linked increased Omega-6 intake to cancer (28, 29).
  • One study shows a very strong correlation between vegetable oil consumption and homicide rates (30).
  • The Omega-6:Omega-3 ratio in blood has been found to be strongly associated with the risk of severe depression (31).

This is just the tip of the iceberg. Inflammation, and therefore vegetable oil consumption, is associated with a wide range of serious diseases and it is beyond the scope of this article to cover all of them.

I am personally convinced that vegetable oils (along with added sugars and refined wheat) are key players in the epidemics of chronic, Western diseases, which are currently the biggest health problems in the world.

Take Home Message

If you want to be healthy, feel good and lower your risk of serious diseases, then you should avoid vegetable oils as if your life depended on it (it does).


  1. Plus, vegetable oils are not yummy!

    Great article.

    • Wish I could stomach coconut oil, water, milk, flour and oil. Any suggestions on how to build up a tolerance for it would be much appreciated.

      • I’m not sure that it would be necessary. Many (most?) of our ancestors lived far away from coconut growing regions and lived very full lives.

        I use butter, even with a dairy allergy, and light olive oil. (The brand I use as practically no olive taste, which is awesome to me. I’m also assuming it’s “human friendly” oil as all you do is squeeze the olives to get the stuff out.)

        Any, that chart suggests that fatty fish are another excellent way to get the right oils in your diet.

        I don’t know — there’s healthy food that I’m allergic and/or react to. (Nuts come to mind.) I tend to avoid rather than worry about it.

        • Sorry, but ‘light’ olive oil falls into the same category as other plant oils, as it’s incredibly over processed; for the oil to have any beneficial effects you MUST use extra virgin, as that’s oil from the first pressing. An OO labelled ‘light’ could have been pressed up to a half-dozen times.

          You need it as unadulterated as possible. You may as well be using canola, sunflower or veggie. Light refers to the colour, and the lighter in colour an oil, for the most part, the more heavily processed – and, therefore, unhealthy – it is.

          (http://www.marksdailyapple.com/healthy-oils/ for info on healthy/unhealthy oils).

          • Well, possibly. Then I’m making the best of a bad lot of choices, because I really don’t like the taste of olives or extra virgin olive oil. I’m sure most of the nutrients are in the first pressing, but it’s moot if I can’t make myself eat it.

            At any rate, the last pressing of olives (especially if it’s cold pressed), doesn’t seem like it really compares with something that needs a weird set of chemicals and/or heat treatment to get the oil out. Maple syrup comes in all sorts of grades depending on when it’s tapped in the season. That doesn’t make Grade B comparable to the brown corn syrup that passes for the real stuff. It maybe the dregs of the olive oil world, but at least olives still just need to be squeezed to get the oil out.

      • There are mildly refined (expeller pressed) coconut oils out there that have no flavor, have all the benefits of coconut oil, and can be used in cooking, etc. Start low, but work up to at least 2 to 3 tablespoons of the stuff per day. CO is high in Lauric acid, which breaks down to mono-laurin, which has anti microbial properties, one of the many benefits of coconut oil.

        • Why? Did the vast majority of our ancestors need to consume 2 to 3 tbsp of it a day? I imagine those who did have access to the stuff didn’t down it in spoon form daily. If you’re otherwise healthy and avoiding most of the bad fats I still don’t see how picking one product that must be flown from 1/2 across the Earth would dramatically improve it.

      • Julia – You list “flour” in the list of things you can’t “stomach”. If you will try, just for a couple of weeks, COMPLETELY eliminating wheat, in all its forms, from your diet, you might well discover that consuming that one unhealthy food is actually behind most of your digestive challenges. Believe me (speaking from experience) it is worth a try!

        • You are so right Debby. I have been so ill for years. Bloated, heartburn (I mean 2-3 purple pills a day with tums in between), worsening arthritis, miserable joint and muscle pain, toilet issues and continually gaining weight. I honestly ate very little food as I was so miserable any time I tried to eat anything. I also ate very naturally, no sodas, no packaged or processed food and no fast food.

          However, as the heart burn was so awful I’d have toast or plain crackers to help settle my stomach. WRONG! Stepped away from gluten/wheat and after 2 months I absolutely Can Not Believe how well I feel!!! Everything is better, everything. I am amazed and becoming more educated based on my results. I’d recommend stepping away from wheat, as Debbie suggests, you may be surprised.

  2. So where does ground flax seed fall in regards to this topic? I love the fiber content but the nutrition facts tell me that two tablespoons have 4 grams of polyunsaturated fat and only one gram of monounsaturated fat. Should I just avoid it???

  3. Kris,

    On point as usual. Thanks for posting this. Don’t know where you find the time!

  4. Great article again. Love the way you set things out, it makes the information easy to read and digest, (no pun intended).

    Vegetable oils are definitely a no go do NOT buy area. Just wish more people out there would take the message more seriously. Their health and well being depends on it.

    All we can do is keep spreading the good information on how health can be improved by making far wiser choices.

    All the best, Jan.

  5. Hi Kris, another great post up to your usual high standards! Another strike against canola oil is that virtually all canola oil sold in North America is GMO. I love how the Canola Council of Canada softens it and says on their website: “Remember – the canola plant has been modified, not the oil”. :)

  6. John Firth says:

    Extra virgin, cold pressed rapeseed oil is absolutely fantastic. The Omega 3-6 ratio is acceptable if not ideal. Highly recommended.

  7. What about olive oil? It’s supposed to be healthy, but according to wikipedia the omega 3 to omega 6 ratio is 1:11!


    Is olive oil bad?

    • The ratio is unfavorable, but the total amount of Omega-6 is still pretty low, so olive oil’s total contribution to your Omega-6 intake will be insignificant. I wouldn’t worry about it.

    • If I may play devil’s advocate here, theoretically olive oil is just another product of agriculture. If you stumbled one in nature, you’d just eat the olives in season and move on. Pressing them is what a farmer would do.

      It might not be entirely wrong to think our love affair with farmed vegetable oils started with the humble olive tree. Or that, as an unsaturated fat (aka non-animal/solid fat) it may not be the best fat for us.

      I’m not sure I believe what I just wrote myself and certainly science doesn’t entirely back me up. But… the more self-consistent view is that saturated fats (aka animal/coconut) are good energy source for us and all plant based (unsaturated) oils should only be eaten with their respective containers (like olives).

  8. DaftMuppet says:

    The link says in the very first section: “However, many studies have now demonstrated that these oils can cause serious harm (1).” So I followed the reference.

    Reference (1) says that a bad ratio between omega 6 and omega 3 increases the chance of many harmful diseases. Specifically, they say that in western diet, the ratio of 6 to 3 omega fatty acids is 15/1. Humans evolved on 1/1 and so is considered ideal.

    So we eat 15 times more of the omega 6 than the omega 3. This causes an increase in many diseases. It continues to say that a lower ratio “exerts suppressive effects”!

    Not just that, but: “In the secondary prevention of cardiovascular disease, a ratio of 4/1 was associated with a 70% decrease in total mortality.”

    So 4/1 has to be good for you, obviously. So I ran to the cupboard to get my bottle of 100% pure canola oil to see how badly I’m killing myself. The ratio is 2/1.

    Clear heart, clear conscience.

    Keep in mind canola oil is supposedly the best oil to use in cooking, and the ratio may be different in others. I will look into it. And will look at the rest of the article.

    • If it is cold pressed, then it’s not nearly as bad as the commercial type.

      That being said, canola oil contains mostly ALA, the plant form of Omega-3, which humans don’t convert efficiently to the active forms, DHA and EPA.

      It is therefore a vastly inferior source of Omega-3s compared to a source like fish oil.

      Plus it contains a high amount of PUFAs. We want both the ratio to be balanced and we want a relatively low amount of each, both Omega-3 and Omega-6.

      Definitely do NOT use it for cooking. Like I mentioned in the article, PUFAs are easily susceptible to oxidative damage during high heat.

      Canola isn’t quite as bad as the other ones (especially if it is cold pressed), but it still isn’t something you should eat in large amounts IMO.

      I’ve got an article coming up soon on the best way to balance your Omega-6s and Omega-3s, will cover this in detail then.

  9. Hi! Thanks for this vital information. Please give us some ideas of which olive oils are good for you. I’ve read some articles saying the U.S. has been getting cheap & “artificial” olive oils, many containing trans fats, for many years, so could you recommend some ways to help us determine which olive oil is the best?

    I was anti-canola & vegetable oil & switched to safflower & sunflower oil, thinking I was choosing healthier options for my family. It is all so confusing! I’ll stick with coconut oil for now. Thanks again!

  10. So does that mean that flax seed oil, chia seed oil, and rape seed oil are good for you? (or at least “less bad” than Canola, soy bean, sun flower, and corn oils?)

    I read an article that said that olive oil has some negative effects as well, such as slowing down blood circulation (up to 30%), even though this could be decreased by combining it with vinegar if I am remembering correctly…

  11. What about peanut oil?

  12. Another great article Kris, thanks for sharing so much vital information on such a regular basis. It’s worth noting everyone that’s asking about specific oils here, if you are using them for cooking then all vegetable seed oils are unstable at high temperatures and that includes hemp, flax and olive oils. Nut oils and nut butters are better for cooking, of which coconut oil is by far the best. A cold pressed extra virgin olive oil is probably the healthiest of all the vegetable oils but if you cook it, it’s no longer cold pressed so just use it for dips and dressings.

  13. What about Shea butter? Raw, unprocessed…

  14. DaftMuppet says:

    To say that saturated fats are harmless is just bad advice. As your reference (16) says: “Lifestyle advice to all those at risk of cardiovascular disease and to lower risk population groups, should continue to include permanent reduction of dietary saturated fat and partial replacement by unsaturates.”

    • Saturated fats are harmless, there is overwhelming evidence to support it.

      The Cochrane reviews are weird like that. The stuff they put into the “conclusions” isn’t always in accordance with the data, which clearly shows that there is no statistically significant reduction in mortality or cardiovascular mortality.

      “There were no clear effects of dietary fat changes on total mortality (RR 0.98, 95% CI 0.93 to 1.04, 71,790 participants) or cardiovascular mortality (RR 0.94, 95% CI 0.85 to 1.04, 65,978 participants). This did not alter with sub-grouping or sensitivity analysis.”

    • Saturated fats are not only harmless, they’re essential for good health, just like cholesterol: – http://www.marksdailyapple.com/fats/

    • Kris

      Is there any way to (fairly) accurately calculate your O3:O6 intake? Since I’ve been sick, I can’t tolerate EVCO, or MCT oil, but I can tolerate butter (goats) and other non-cow dairy. I also know I’ve been eating FAR TOO MUCH rapeseed oil, so I know it’s going to be fairly stinky. It’s a bit difficult to eat right when you’re unable to manage the stairs too often!

      I need a fairly accurate appraisal, I can’t go with a guesstimate (it’s the Asperger’s – it makes me pedantic). Need to know how many of NOW’s Super EPA caps I need to lob down me neck (WHY are O3 caps so HUGE…?! Why can’t they be tiny, like D3?!)

      Finally, is it better to have a brand which is more EPA than DHA? Keep reading conflicting info on this; some say yes, some say it doesn’t matter…

      Cheers, matey-dude!

  15. Loved it Chris ….. I am 86, disabled but other than that my vitals are A1 so I know that I am on the right track.

    Joe in Sydney, Australia.

  16. Thanks KG! As per usual, great info.

    I’m trying to compensate for all the MANufactured foods we eventually eat [esp. in Ca!] by consuming 3 or more grams of [m.distilled] FO Omega-3 capsules; BUT, that’s only guess-work.

    Look forward to your take on how to compensate, as “out west” we probable never see pasture raised meat in a typical restaurant. [let alone avoid the onslaught of Omega-6 oils in their recipes!!] So far, my new weight/BP/BG numbers are all much better since going paleo/minimizing seed oils & wheat. Sites like yours help immensely.

  17. I’m not sure if this is helpful, but I was at a store in Portsmouth, NH, Leroux Kitchen, their website is LEROUXKITCHEN.COM. I asked and was told their olive oils are all natural & organic, direct from their distributor. They have different kinds of flavors, since they are infused with various ingredients.

    I tasted several and was quite impressed. They also have organic {nitrate-free} balsamic vinegars, also infused with a variety of flavors. I bought 5 different flavors of the Balsamic vinegars!! They were all s-o good, I would’ve bought more and intend to next time or via their website!!!

    I usually wouldn’t promote a website, but felt it was in accordance with the article. I’m sure there are many places where one could find the “good” olive oils. I will try to find a site recommended in another article I read about olive oils and their purity, etc.

  18. I have known that for quite a while and as a grown-up, always cooked with butter (clarified or not) and duck fat and used EVOO for salad dressing only (when I eat a salad, which is not that often).

    I do have some coconut oil somewhere in my pantry, which I use sometimes, but I am not a big fan of cooking with it because of the flavor. For smoothies, it is quite nice to add in some CO but this time, precisely because of the flavor. But apart from that, I like to eat the whole foods (avocado, olives, etc) instead of using the fat only.

  19. Carl Ashlock says:

    I appreciate the fine spirit in this blog and agree with most everything. However, for years I have addressed high cholesterol, hypertension, etc. and followed my doctor’s regimen of ‘drugs’ to keep things in check. Until I finally became fed up with the many ‘side-effects’ and asked my doctor how long I would need to take these drugs. His reply angered me, “For the rest of your life”.

    I read Caldwell Esselstyn’s wonderful book and after throwing away my prescription drugs and going on a completely plant-based, dairy-free, meat-free, and OIL (any ‘processed’ oils including olive and coconut), within three weeks my blood panel showed a very significant improvement in every area.

    Since I love olive and coconut oil and somehow felt that they were different, I began to ease back into taking them, and my blood panel immediately began to rise. I think, at least, for me I’m going to stick with a completely all processed oil-free diet.

  20. Hahaha (how it’s made video). That is hilarious, that canola oil comes from the canola plant. Canola plant does not exist, it’s from a plant called rapeseed (brassica napus) which is poisonous to both humans and animals and is a great form of insecticide.

  21. Thanks for all your posts. Does anyone know if there is a blood test for fatty acids omega 3 and 6? I have celiac and am off processed foods. I’ve been eating only grass-fed meats and dairy and butter, coconut oil and extra virgin olive oil. My eyes got severely dry and worsened whenever I ate fish or chia. Can your balance go too far in the wrong direction?

    Also, for those who dislike olive oil, I was like that. Now I love it. I subscribed to an olive oil club that mails it to you fresh every 3 months from different parts of the world. I love the taste now. It’s like I love garden tomatoes but hate the pale tomatoes in the store. I read the fresh extra virgin olive oil has health promoting compounds that degenerate over time from shelf-storage.

If you made it all the way down here, you probably liked the article. Please share it:

Speak Your Mind