The Worst Cooking Oils For Your Thyroid: Use These Instead

The Worst Cooking Oils For Your Thyroid: Use These Instead

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Will eating fat help your health or hurt it? What about your thyroid?

The truth is that it really depends on what type of fat you are eating. 

But let’s be clear: the consumption of fat is essential for your body. 

Certain fats, called essential fatty acids, can not be created by the body and are required for very important cellular functions like promoting brain health, regulating metabolism, improving cognition, and more. 

Fat also provides your body with a source of calories and is one of the most potent regulators of appetite. 

All of this information is generally well-known. 

What isn’t as well known, is the negative impact that using the wrong types of fat can have on your body and your thyroid. 

I would even go as far as to say that the consumption of inflammatory oils may be a leading cause of chronic disease and inflammation that most people just aren’t aware of.

It doesn’t matter what type of health condition you have, eating the wrong type of fat can make it worse. 

And this is especially true for thyroid patients who tend to be more prone to inflammation than the general population. 

What makes this even more concerning is the fact that the majority of fats that you are coming into contact with fall into this inflammatory category and may be damaging your health and making your thyroid problem worse. 

Here’s why:


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#1. These Unhealthy Fats Are Found Everywhere (And In Everything). 

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The most unhealthy fats that you can come into contact with are often labeled and marketed as vegetable oils but this naming convention couldn’t be more misleading. 

The name vegetable oil gives you the idea that the oil came from something healthy, like a vegetable, which is exactly what the manufacturers of these oils want you to think. 

But the reality is that these fats are so processed that they barely resemble the plant or seed that produced them. 

For this reason, I think a much better name for them is industrial seed oil. 

But, as you might have guessed, the name industrial seed oil doesn’t sell well, which is why you’ll see them marketed as vegetable oils. 

But, as I mentioned, don’t let the highly misleading naming convention that they choose to use confuse you. 

Whether you refer to them as vegetable oils, industrial seed oils, cooking oils, or some other name, these are the most unhealthy fats that you can consume and they should be avoided. 

What types of cooking oils fall into this unhealthy category?

Allow me to introduce them: 

  • Canola oil
  • sunflower oil 
  • Safflower oil
  • Corn oil
  • Soybean oil
  • Cotton seed oil
  • Grapeseed oil
  • Rice bran oil

These cooking oils are by far the most toxic of all cooking oils available and they are found all over the place. 

If you don’t believe me, walk into your kitchen right now and start reading the ingredient list on the back of any processed food. 

Unless you are a seasoned ingredient label reader and know how to identify healthy food, I can almost guarantee that these oils are found in your house right now. 

There’s one reason for this: 

They are dirt cheap. 

Compared to healthier oils (which we will soon discuss), these oils are neutral (so they don’t alter taste), cheap (so manufacturers can make money), and easy to purchase in bulk. 

As a result, they are found in all sorts of foods and are heavily used in restaurants. 

This, by the way, is one of the main reasons that eating out is so unhealthy!

Have you ever found a restaurant willing to cook everything with extra virgin olive oil? 

If they used healthy oils, they’d have to increase their prices considerably. 

So the easier option is to just use low-quality, cheap, toxic cooking oils to keep their prices low. 

But, believe me when I say, if you eat these foods you will pay the price at some point. 

Part of the reason that these oils are so toxic has to do with their creation process. 

It’s well known that the more processed a food is, the less healthy it is for the body

The creation of industrial seed oils requires a multistep process that involves heating, dissolving, deodorizing, and the addition of chemicals to get the final product that you then cook with and put in your body. 

It’s no wonder why these oils cause so many problems when consumed.

The processing of these oils isn’t the only problem with them though which leads us to…

#2. Unhealthy Fats (Industrial Seed Oils) Contain High Amounts of Omega 6 Fatty Acids.

One of the biggest issues with these fats is their high concentration of omega-6 fatty acids. 

In your body, there exists a ratio between omega 3 fatty acids and omega 6 fatty acids. 

This ratio may not mean a lot to you but it’s really important when it comes to regulating inflammation. 

We know from research that higher levels of omega-6 fatty acids push on the gas of the inflammatory cascade (1). 

This is both good and bad. 

Bad because it means that eating these oils can lead to inflammation. 

But good because it means that avoiding them can positively impact inflammatory levels in your body. 

And this is a great thing for your thyroid health. 


Your thyroid gland is very sensitive to changes in inflammation to which it responds by reducing thyroid function

The more inflammation in your body, the worse your thyroid will function. 

Beyond the thyroid issue, inflammation is at the heart of just about every chronic disease you can think of and the use of these oils may either be contributing to their creation or making them worse. 

#3. They (Seed Oils) Stick Around in Your Body For a Long Time. 

Remember: your body stores excess calories and energy as fat. 

In addition, it also uses fat to protect your cells by incorporating them into your cellular membranes (2). 

Why is this important?

Because industrial seed oils, as a whole, are considered polyunsaturated fats which means that their chemical structure has a lot more double bonds than saturated fat. 

And these double bonds act as a point of weakness and as a point of potential oxidation. 

It’s easy to imagine a scenario in which the consumption of these fats allows for their incorporation into your cellular machinery. 

Do you think that their points of weakness will keep your cells healthy and functional or that they will hurt them in the long run?

Obviously, the latter, which is why they should be avoided. 

The problem with consuming these fats is that they do get incorporated into your cells where they can sit around for a long period of time. 

And all the while they are open to damage and oxidation from regular day-to-day activities. 

As they get damaged, they weaken your cell walls and compromise cellular function. 

This, in my opinion, is probably their worst attribute: 

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Their ability to promote oxidative stress. 

Oxidative stress is bad for all of your cells but it’s exceptionally bad for your thyroid cells. 

The low thyroid state compounds the effects of oxidative stress (3) and adding further fuel to this fire will certainly not help thyroid patients. 

The good news is that as you avoid industrial seed oils and fill your body with healthy fats, they will take the place of these unhealthy fats in your cells and in your fat tissues over time, resulting in better health for you overall. 

The only downside is that it can take several months to turn over and replace these unwanted fats. 

#4. The Reheating of Industrial Seed Oil Results in The Creation of Toxic Byproducts. 

On top of being inflammatory all by themselves, industrial seed oils are often heated and reheated by both restaurants and the at-home cook (4). 

This process takes an already unhealthy base and makes it even more unhealthy. 

Heating oil destabilizes it, changes its structure, and results in the creation of polycyclic aromatic hydrocarbons which are potentially cancer-promoting. 

Because these oils are so cheap and because they are frequently used by fast food restaurants where they are repeatedly heated and reheated for frying, they are prone to creating these toxic byproducts. 

Add this to the fact that these oils are highly fragile and more prone to oxidation, you have a double whammy, and not in a good way. 

This means that even if you aren’t reheating them over and over again, they are still causing problems compared to their unprocessed counterparts (more on this in a minute).  

#5. The Conventional Food Establishment Is on a Mission To Convince You That These Fats Are Healthy. 

I’m not necessarily claiming malicious intent here, but there seems to be a push to try and get as many people as possible to consume these oils by calling them heart-healthy

You can find this information on all sorts of major websites and organizations including the American Heart Association where canola oil is touted as one of the most heart-healthy oils available. 

It’s easy to look at this information and come to the conclusion that these oils must be healthy because why else would the American Heart Association promote them?

What makes this more confusing is the fact that there are plenty of studies that seem to suggest that these oils are, in fact, heart-healthy (5). 

You can read through all of the research and competing viewpoints when it comes to these oils but let me tell you how I think about it: 

With record levels of thyroid disease, obesity, diabetes, and chronic disease in general, do you honestly feel like the standard dietary advice is working?

It’s hard to look at the data over the last 20 years and claim that the standard advice is worth something when we see that heart disease continues to be the number one cause of mortality in developed countries.

We know for sure that people are eating more of these oils than ever before, so it seems suspicious that heart disease continues to rise. 

But beyond this, do you think it makes sense to consume an oil that has undergone 15+ different steps in order to be palatable to humans 

Or does it make sense to consume a cold-pressed oil from an unprocessed source?

It’s clear that processed foods directly correlate with disease so why would processed oil be the only exception?

I’ve spent a lot of time reading, researching, and experimenting with my own body and I’ve come to the conclusion that eating the least processed version of food is always the best option. 

And part of the reason that I know this is because I’ve tested both options!

I feel so much better when I avoid processed foods and when I avoid industrial seed oils. 

And if you are someone who has not been feeling very well or is suffering from thyroid disease or other chronic diseases, then it may be time to try something like that out. 

But at the end of the day, you’re an adult and you can make whatever decision you want. 

Eat These Cooking Oils For Better Thyroid Health

If you’ve found this information interesting and you want to try and avoid your exposure to these unhealthy cooking oils then here’s what you’d want to replace them with: 

  • #1. Extra virgin olive oil – This (truly) heart-healthy oil has been used for thousands of years and is a big part of the Mediterranean diet which is known to be anti-inflammatory in nature. It contains a rich source of oleic acid and polyphenols (such as oleocanthal (6)) which impart beneficial anti-inflammatory, anti-cancer, anti-atherogenic, immuno-modulatory, neuro-protective, and hepato-protective benefits (7). In other words, this cooking oil is great for your entire body. 
  • #2. Cold-pressed coconut oil – This oil is loaded with medium-chain triglycerides (8) and has additional benefits like acting as an antifungal, antiviral, and antibacterial agent. 
  • #3. Grass-fed butter or ghee – These foods contain conjugated linoleic acid and fat-soluble vitamins like vitamins A, D, E, and K2


This is just a list of cooking oils so make sure to also get as many healthy fats as possible from your diet, especially omega-3 fatty acids, from whole foods like fish, meat, nuts, and seeds. 

Eating these minimally processed oils and fats will provide benefits to your thyroid and body in more ways than one. 

And if you don’t believe me, you can always give it a test. 

Ditch the industrial seed oils for 30 days and see what happens when you only consume the fats listed above. 

I can promise you that eating extra virgin olive oil for 30 days is NOT going to cause any serious problems, but ditching industrial seed oils has a big chance of helping you feel better. 

The risk vs reward ratio here is pretty lopsided in your favor.

If you are someone who has been eating a lot of these inflammatory oils then you might also want to take steps to reduce inflammation in your body. 

If that’s the case then I would strongly recommend checking out this article next which highlights the most powerful anti-inflammatory supplements available

Now I want to hear from you: 

Were you aware of the potential danger of these oils?

Are you someone who is already actively avoiding these oils in favor of other cooking oils?

Are you planning on making any changes to your diet after reading this? Why or why not?

Leave your questions or comments below! 

Scientific References









These cooking oils are damaging your thyroid

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About Dr. Westin Childs

Hey! I'm Westin Childs D.O. (former Osteopathic Physician). I don't practice medicine anymore and instead specialize in helping people like YOU who have thyroid problems, hormone imbalances, and weight loss resistance. I love to write and share what I've learned over the years. I also happen to formulate the best supplements on the market (well, at least in my opinion!) and I'm proud to say that over 80,000+ people have used them over the last 7 years. You can read more about my own personal health journey and why I am so passionate about what I do.

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41 thoughts on “The Worst Cooking Oils For Your Thyroid: Use These Instead”

  1. Good Morning!
    I feel like I’m obsessed with your site and all the info you have to provide on hypothyroidism! Currently (slowly) changing my diet so as not to trigger any migraines…but its been 2 weeks of gluten free & mostly whole foods…..excited about how I feel, hoping to begin adding some of your supplements after a month of my new diet but i digress…was wondering if Avocado Oil would be considered a seed oil or if it is healthy like olive oil? I thought it was healthy and has the benefit of a higher flash point than olive oil but I really have no clue!
    thank you & happy saturday

    • Hi Megan,

      Avocado oil is not a seed oil and would certainly be superior to them, but I wouldn’t put it on the same level as olive oil or the other cooking oils I mentioned in the article. There’s a place for using it with higher heat, but it suffers from problems such as being adulterated with other oils.

      There was a study that showed that some 70% of private avocado oil brands tested were either rancid or were adulterated with other oils. For these reason, it’s hard to suggest it because better alternatives exist.

  2. Do any cooks or bakers out there know what is best for baking when oil is called for? I thought grapeseed oil would be okay but not according to Dr. Childs.

    • I have this same question. I have been using grapeseed oil to bake some keto cakes. After reading this, I thought that avocado oil would be healthier if it is an unrefined, cold-pressed brand. Now I am unsure if it is okay or not to bake with avocado oil.

    • How about using coconut oil? It really doesn’t leave too much taste and anyway you can get by with much much less than the recipe calls for and still come out great. A little dab when cooking goes a long way. Think of substituting a few tablespoons rather than in terms of cups/half-cup the recipes call for when baking.

  3. I had thought according to other holistic health experts that grapeseed oil was preferable as a cooking oil vs olive oil, since it could withstand higher heat. Is there a certain temperature at which olive oil becomes unhealthy? Can it be used for cooking on the stovetop as well as baking?

    • Hi Lauren,

      Extra virgin olive oil has a smoke point of around 410 degrees Fahrenheit. While it is true that heating olive oil beyond this temperature will result in some oxidative damage, the polyphenolic compounds naturally found in olive oil provide protection from oxidants that may be created during this process. Given this, it’s really not a concern.

  4. hi dr childs
    i take xyogen t 150 one a day,my last t tests came out good i get my
    bloodwork from veterans,then i see it on line.
    i also take so many great liquid minerals daily,fulvic -humic ,all of them

    i got my tryg down 52 points to a great 99 ,i was 149 before.
    my ? i see ancseteral supp sells liver and thyroid 40 mg caps.i was thinking of changing to them,their cheaper.but il l keep wht im doing
    i do take reg liver caps,maybe i should leave it alone?

    • Hi Jack,

      More important than your labs is how you are feeling. It’s very possible to have relatively normal or even good looking labs while still experiencing the symptoms of hypothyroidism.

  5. Thank you for this excellent article. As a medical professional, I am very pleased to read your informative evidenced based articles. By the way, the American Heart Association will allow you to use their logo for a “donation.” I know this because 10 years ago they said I could with a $25,000 donation. I couldn’t do that so I wasn’t able to get the endorsement.

    • Hi Mc,

      That is not correct. All cooking oils will start to degrade above a certain temperature, known as the smoke point, but this isn’t specific to olive oil. It’s also not true that just because a smoke point is reached that the oil being heated becomes harmful. Olive oil, for instance, contains beneficial anti-oxidants that counteract the effects of oxidation that may occur while heating it. The result is a built-in mechanism of safety. The same cannot be said for highly processed oils which have had all of their natural anti-oxidants removed (if they even contained any, to begin with).

  6. Hi doctor,
    What about palm oils and palm kernel oil?? They’re in a ton of health food items but I thought these were questionable also. Another couple I didn’t see on your list is peanut oil and sesame oil. Thoughts on those, please?? Thank you.

  7. Dr Childs I’ve read many articles that say to watch out for fake olive oil and that even the ones labeled “extra virgin” are adulterated with other cheap oils. There is a lot of fraud in the olive oil industry it is claimed and that getting 100% true fresh olive oil is difficult and the price would be extremely high. All the major big brands are fake and even the smaller bottlers are not honest. I bought a “private label” specialty brand which claimed it was from a family farm, etc. but the oil did not even smell or taste right. It was downright yuk. Even the brands sold at the health food stores are out in the light and on the shelf for weeks if not months and I don’t think it’s possible to know the true quality. One can waste lots of money buying and tasting. I would not cook with olive oil either as it’s not heat stable. Only use it as a finishing touch on dishes.

    • Hi Dee,

      As long as you are getting extra virgin olive oil that is cold pressed with quality certifications then you can be sure you are getting a solid product. These recommendations won’t ensure you are maximizing polyphenol content but it will ensure you are getting a high quality product.

  8. In UK, it is hard to find cold pressed olive oil on the supermarket shelves , but what we do have is cold pressed rapeseed oil. It is supposed to have higher omega 3 content than olive oil. It is not chemically processed.
    Regarding the paragraphs on reheated oils, that is more a warning to not use restaurants or takeaways.

    • Hi C Bear,

      Yes, that specific point is more about avoiding restaurants, but the point still stands: those oils are far more prone to oxidative damage compared to cold-pressed oils. And it’s the oxidative potential which is probably what causes the majority of issues when consuming processed oils.

      You are welcome to use whatever oil you want, I just don’t see any good argument for consuming rapeseed oil but there are plenty for consuming olive oil:

  9. Thank you for this valuable information
    To be honest I used these type of oils many years ago specially canola oil because hey! You see de American heart association logo on it and you would think it is a good oil to use, not anymore
    Mostly I use avocado organic avocado oil, but it’s not in your healthy list
    So it’s safe to cook with extra virgin olive oil? I was trying to avoiding it because the oxidation issue
    I have hashimoto thyroiditis and I want a safe option

    • Hi Alma,

      Yes, it’s definitely safe to cook with extra virgin olive oil. It has a smoke point of 410 degrees Fahrenheit so it can withstand moderate heat. In addition, it’s loaded with polyphenols that protect you against oxidative damage.

  10. I have discovered that any industrial oil is very disruptive to my IBS. It’s taken years to realize this but if I avoid it my digestion is almost completely free of any issues. It means I cannot eat at any restaurant but it’s worth the sacrifice!
    I do use Avocado oil and I’ve heard that some brands adulter it with other oils. Are you aware of any brands that are pure?

  11. I cook with all the right oils but its the problem is the processed foods..So i just went and threw out anything with those oils..I use your products even though its so hard for me to get them where i live in Costa Rica..I share your articles with friends because they are so helpful..thanks

    • Hi Connie,

      Good for you! I think that’s the best place to start, by throwing away anything you don’t want in your body.

  12. I knew about these oil and I will not use them. My sister gives me grief for this because she thinks I am being high-faluting when I buy extra virgin olive oil and unrefined coconut oil. There are also brands I won’t buy such as those without processing dates or certifications. I do like avocado oil and I haven’t heard anything negative about it, so far. Admittedly, I have not gone looking for problems with it. Are there any issues with avocado oil that I should be aware of? Should I stop using it? Thanks for any information you can provide!

    • Hi Katherine,

      The biggest issue with avocado oil has more to do with the fact that most brands contain rancid or are mixed with non avocado oil, not the fact that avocado oil is inherently harmful. It’s certainly not a top tier oil, but you can get by with using it occasionally, provided you are actually consuming avocado oil and not some adulterated counterfeit.

  13. Dr Child’s, I use your T2 supplement and followed Gundry on his oil recommendations, you both have same number 1 choice EVO. Thanks for itemizing and explaining the negatives of the bad oils. I’ll likely ask waiters what oil is used and make better menu choices now.

    It would be very helpful if you made distinctions between thyroid gland function and thyroid hormone processing in your articles as a 30 year radiation injury dead thyroid gland reader. Thanks!!

    • Hi Bruce,

      In general, I will use the term thyroid function when referencing any therapy that improves thyroid function for all those who have low thyroid levels (including those post RAI and post thyroidectomy). If that distinction isn’t made clear, it’s pretty safe to assume that any information directed at hypothyroid patients also applies to those people in your situation. This isn’t universally true, but if you make that assumption you will be correct far more often than you would be incorrect.

  14. Hi Dr. Childs,
    I only use the good oils and grass fed butter you mentioned, and I buy very little processed foods. Everything I buy is organic. However, there is an organic bread with organic, cold pressed, canola oil and an organic cracker that has organic sunflower oil that I occasionally buy, does that make a difference? Or are they still as inflammatory and harmful? Thanks

  15. hello, Dr. Childs, this was quite an interesting article. I’ve got Hashimoto’s with hypothyroidism as well as osteoarthritis and some other arthritis in my neck. I have been trying to find ways to reduce inflammation as the pain management that my doctor has me in doesn’t really address the problem. I am looking forward to taking these seed oils out of my diet and trying some of the supplements you mentioned. Thank you!

  16. This explains why every time I eat takeout I not only swell but the next few days my body aches. I feel stiff and my body aches especially after eating the most popular take out restaurant food. Even some grocery store deli foods have the same effect. I sometimes travel for work and have traveled with a cooler of cooked frozen meals to avoid these problems.

  17. Dear Dr. Childs,

    Yes I have been aware of the industrial oils for about a couple of years. I have been avoiding them. I also use Palm oil, which I believe is a great oil. I have been really ill with Mercury Poisoning for many many years, I am getting better and better each day for years now, getting rid of many parasites that I can see (100’s of them, I have pictures) with Mimosa Pudica Seed capsules. I had an OAT test over a year ago, which showed that I have not been able to get rid of fats that are challenging my health. Do you know is there any other way to help remove the fats in my body that are causing havoc?

  18. Since sunflower oil is bad and those industrial oils trigger my IBS; I am wondering if raw sunflower seeds are also bad to consume and could trigger IBS the same as sunflower oil?

    • Hi Patty,

      You’ll have to experiment to see if you can tolerate the seeds. Because the seeds aren’t as processed as the oil, they are far less likely to cause issues.

      • Thank you. I’ve also realized that sunflower seed butter is also a big trigger. It must be because of the processing used in making it.
        I have been aware of the digestive issues from these oils but I’m excited to see if total elimination of them will keep thyroid symptoms at bay as well. Never associated them with my thyroid imbalances. Thank you for this article.

  19. I just found out about this a few months ago from reading Dr. Mercola articles. He references Ray Peat and his research on this so there is specific research that tells us this.
    My problem is it is very, very hard to find food without these oils and as was said earlier, it’s hard to find EVOO that isn’t adulterated and can still fit in my budget. I did buy some expensive EVOO but mostly I just started using lard, tallow, Kerry Gold butter and I just bought some MCT oil to use in my tallow lotions.
    I do use mayo with avocado oil in it since I can’t seem to find anything else. Still looking or maybe will try to make my own.
    It’s been about three months since I stopped eating anything with these oils (PUFAs). I’m sure I’m getting them somewhere but I’m actively trying not to. I’m not sure but I’m thinking I may need to lower my thyroid meds now. My husband had a stent put in this year so he is following the same diet. We have read this can also help plaque in arteries. I’ll know next month when I get my bloodwork done. Fingers crossed!


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