Everything You Need To Know About Bad Oils

We’ve all heard of “bad” oils by now: how we should avoid them at all costs, and instead use butter, ghee, avocado, coconut, or olive oil in their place, and how it’s imperative to ask restaurants to use a different (healthy) cooking oil in their place when eating out.

However, what is it exactly that makes bad oils so bad? First off, the “bad” vegetable oils (corn, cottonseed, canola, safflower, sunflower, soybean) aren’t always where you think they might be. Oftentimes, they’re hidden, lurking in organic foods you would never even think would contain this unhealthy ingredient, like oat milk and other nut-milk blends. They’re also very frequently infused with olive oil, to make a “blend” that restaurants can use to save money….at the expense of your health. Kind of like mystery meat, but with oil…and this lack of transparency concerning oil in the food and restaurant industry makes you wonder: is it really worth trusting strangers to the point where you feel comfortable putting your health in their hands? Still, while I do strive to eat as cleanly as possible and always make an effort to focus on nutrient density above all else, there is something to be said about the benefits of letting go and living a little every once in a while. Is it really going to harm you that much if you just have some sweet potato fries every once in a while, even if they’ve most likely been fried in canola oil?

Luckily, Dr. Cate Shanahan, resource extraordinaire for all things health and nutrition, has made multiple appearances on the B.Rad podcast to share the true facts on How To Become Cancer-Proof and The Four Pillars of Health, among others. And one thing that kept consistently coming up throughout our different conversations was the topic of certain oils: the ones that have been derived from certain sources, refined through certain processes, and that are known to have specific, highly detrimental effects on human health. They also are unfortunately lurking everywhere, and not just in the obvious places you might think, but in organic dairy-free milks, sauces and salad dressings, condiments, and in countless processed foods like crackers and other snack foods that boast “gluten & grain-free”, “paleo-friendly” and “keto-friendly” labels. And yes, even at so-called “healthy” restaurants. And sure, the actual food at those restaurants could very well be the healthiest assortment of grass-fed protein and produce possible, but if the food has been prepared in these oils, then what’s the point? Doesn’t that just cancel all the health benefits out?

It can definitely get overwhelming trying to sort through all of the information out there pertaining to vegetable oils and how they affect our bodies. So, in the hopes of clarifying things and making it easier for you to see what the true risks are from ingesting these oils, I’ve collected the most interesting and startling facts about vegetable oils that I have learned through research and from the wonderful Dr. Cate Shanahan. Not in effort to tell you what to do, but just so you can see what risks you are taking by ingesting them. And maybe at the end of this, you’ll have decided that it’s really not worth stressing over every little thing, and life is short, so you feel like, hey, I may as well have some fries when I feel like it. Or, maybe this information will scare the pants off you from ever eating takeout again! Either way, the point of this article is to simply present straight facts about vegetable oils like soybean, sunflower, safflower, corn, canola, and cottonseed, so you can utilize this information to make the best, most informed decisions for yourself.  

Let’s start with the scary fact that vegetable oils make up 30% to 40% of the average person’s daily calories. Even worse, our bodies don’t even register these oils as nutrition because they can’t provide our bodies with the kind of energy that other fats do. Dr. Cate also points out that even if you’re thinking you’re healthy because you’re on a keto diet, you still have to be careful about the kinds of salad dressings/vinaigrettes/sauces you use to cook with and add to your dishes. This is even more true when it comes to eating restaurant food, because the food industry is notorious for using olive oil blends that contain vegetable oils, or just using straight up pure canola, safflower, soy oil, etc. I’ve talked about this on social media before, and one follower who sells restaurant supplies commented to share that both soybean and canola oil are at every single restaurant!

One of the major problems with vegetable oils is that they promote cancer. And the reason why they do this is because they go after your mitochondria and actually damage it. When Dr. Cate was last on the podcast, she shared studies that she was citing in her next book that show that “mitochondria cannot function when they have a certain concentration of vegetable oil that they’re supposed to be trying to burn for energy. It shuts them down. They cannot produce energy. And that’s what leads to cancer, in my view.”

Dr. Cate also says it helps to visualize the negative effects these oils have on your body. Canola oil, for example, is a problem specifically because it is molecularly unstable: “If you have too much of it in your diet, it destabilizes and that destabilization is a problem; it molecularly deteriorates.” While Dr. Cate admits this part is a little harder to visualize, she went on to explain that there is something called free radical cascades, which is almost like radiation. She explained further: “It’s almost like it becomes like plutonium in your body, where it degrades and starts flying off these high energy molecules called free radicals that damage your cells. They damage your DNA, they damage your enzymes, they damage everything in your cell, your cell cannot have a chance of functioning properly, and they shut down your cell’s energy production.”

Another major side effect of consuming these oils? Dysfunctional fat metabolism. Our bodies are simply not equipped to handle these toxic oils, let alone such large quantities of them.

According to Dr. Cate, we now have 20 times the amount of linoleic acid (the most common polyunsaturated fatty acid found in vegetable oils) present in the fat in our bodies than we used to have, which has, unsurprisingly, radically altered the composition of our bodies. Dr. Cate reveals: “Our bodies don’t need that stuff so much for energy. We don’t want it for energy. We use it for signaling and we use it for building nervous tissue and for maintaining the proper fluidity of our cell membranes and our body temperature.” She adds, “I think that these oils are a big reason behind the epidemic of thyroid disease. Our thyroid’s are very primal organs and do stuff like maintain our body temperature. And when we’ve changed the ‘melting point’ basically of our body fat, then the physics by which our thyroid operates have been disturbed, and our thyroid doesn’t operate properly anymore.” Dr. Cate has seen tons of patients suffering from thyroiditis, thyroid nodules, hyperthyroidism, and has realized that there wasn’t this epidemic of thyroid disease before vegetable oils came onto the food scene. Further, Dr. Cate says that if you ask a vet who’s been around for 30, 40 years, they will tell you that pets are now starting to get thyroid disease and thyroid nodules, things that they didn’t suffer from before. And it will probably come as no surprise to hear that pet food didn’t used to have ingredients like soy oil in it…that is, until about 10 years ago. 

If you want to get a realistic idea of just how bad these oils are for your health, consider this quote from Dr. Cate: “If you can just get vegetable oils out of your diet, you’re going to do way more good than if you get sugar out of your diet.” Of course, we know how bad sugar also is, and that it’s also highly addicting, but there is a reason why Dr. Cate emphasizes the exclusion of the vegetable oils over the sugar at first. Isolating just the vegetable oils makes that massive of a difference, and not just because they are hidden partially everywhere, but also because of how profoundly harmful they are to our health.

So….if we know from science and studies that these oils are in fact, truly, quite terrible for us, then why can they still be found basically everywhere and anywhere? Ready for the shocking answer?

It’s because of money. OK, maybe that’s not that shocking at all. But, for people who only care about making a profit and don’t care at all about health, the fact that these oils are cheaper than their healthy counterparts is very alluring. And, according to Dr. Cate, that alone is the number one reason why they are so ubiquitous. And if you think about it, if you go to any store and compare the prices (and volume) of say, soy oil to olive oil, you’ll see you can buy a huge amount for less than $20. But think about how much olive oil you could get for the same price….there’s a noticeably big difference.

And here’s a scary stat: smoking a cigarette delivers a disturbance to normal healthy cardiovascular function of around eight hours. Having one serving of French fries can disturb normal, healthy cardiovascular function, make your arteries harder, and lessen blood flow, for up to 24 hours. So, the acute response to French fries and vegetable oil ingestion is worse than sugar and worse than smoking. There are also other facts to be mindful of, like age: one TIME article about the dangers of vegetable oil cited a study that showed the effects of the accelerated oxidation from cooking with vegetable oils is actually strongest for people over the age of 65. In 2015, The Telegraph reported that “scientists found that heating up vegetable oils led to the release of high concentrations of aldehydes, which have been linked to illnesses including cancer, heart disease and dementia.” A different group of scientists researching vegetable oils’ effects compared the aldehydes in food fried in vegetable oil to the aldehydes one receives from smoking cigarettes. Their conclusion? The current level of fried vegetable oil consumption is equivalent to smoking 25 cigarettes per day.

The evidence and research is pretty overwhelming, and the answer is clear: vegetable oils are as bad (and sometimes worse!) for you than sugar and smoking. And yet they are still so present in countless places that it’s hard to imagine our world without them. We’d certainly be better off – heart disease and cancer rates would be cut in two, people would enjoy longer lives, feel better, think more clearly, and feel less depressed and anxious, and way happier. That’s not our current reality, but it’s ok: while the rest of the world may not be up to speed just yet, you’re lucky that you do know the truth about bad oils, so you can proceed with as much (or as little) caution as you’d like. Finally, if you know anyone who is unaware of just how detrimental and ubiquitous these bad oils are, or don’t understand the gravity of it just yet, send them here to read this article — you might just save their life.


Brad Kearns
Brad Kearns
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