For a long time I'd been hearing that the oils used in most salad dressings these days are the least healthy types of oils and that we should never eat oil based salad dressings that we don't make ourselves, however I never really put much thought to it, I figured that it wasn't that hard to get some perfectly healthy olive oil and some herbs and spices and things to mix together into a simple salad dressing so I'd always innocently assumed that all the salad dressing I'd been used to eating my entire life was made that way (despite the fact that my grandma's homemade salad dressing that I knew had olive oil tasted noticeably different). That changed a month or two ago when I had a rude awakening as I looked at the back of the salad dressing in my fridge and noticed that soybean oil was listed as the first ingredient.
Since then I've found myself occasionally trying to find what other things I eat are made out of. Mayonnaise is almost entirely soybean oil, margarine (which I don't eat) is almost always made from soybean oil, and of course almost all restaurants that serve fried food fry their food in soybean oil. Soybean oil has been the most used edible oil in the United States since 1945 and yet when I was noticing all of the things that had soybean oil I realized that I don't think I'd ever seen soybean oil in a grocery store, so the last time I went to one I made a trip to the oil section and found that the only soybean oil there was in the specialty turkey frying oil that is only around for Thanksgiving but that is a soybean and corn oil mix so really you can't go to a typical grocery store and buy a bottle of the most popular oil in the country. (However the restaurant supply store I went to the other day had multiple pallets of it) The most used edible oil in the country is one that most stores don't carry because nobody will buy it. What would cause a product to be so gross that it has to be hidden from us to buy it?
When I was learning the tings that led me to write Margarine is from the Devil I heard Sally Fallon Morell mention that the oils that are being put in our foods were industrial waste products, I believed her but for whatever reason my brain also treated that statement as an exaggeration because that is exactly what an exaggeration would sound like so I chose not to worry about it. But after deciding that I wanted to write this article I decided to see how soybean oil was made and I came across this video showing what happens when soy is processed and the main product focused on here is not the oil but what they call oil cake which is the dry substance left after the oil is pressed out and is used in animal feed, no more emphasis is given on the actual oil after we see it pressed out of the animal feed. This proves Sally's claim, soybean oil is a byproduct of animal feed production, we are being fed industrial waste at a massive scale.
Things get even scarier when you know a thing or two about oil. Oxidation is the chemical process that causes metal to rust but oxidation effects oils as well. As oil molecules break down they become more prone to oxidation, they break down naturally over time but things like light and heat speed up this process (this is why olive oil is sold in green containers and you are told to store it in a cool dark place). Once an oil has oxidized it is considered rancid since at this point it will smell bad and be incredibly toxic because its chemical makeup has been altered. Oils also have different smoke points which is the temperature where they will begin to burn, and while the food industry claims that the smoke point is unrelated to oxidation I find such a claim hard to believe since oxidation occurs as the molecules break down and burning is a process where molecules break down.
So lets take a look back at this video keeping in mind that heating oil causes it to go bad and the specific smoke point of unrefined soybean oil is 160°C. First they take dried soybeans and extract the shells by crushing them up a bit, this is fine. Next they run the crushed soy through a device called an extruder where it is exposed to high heat and pressure, the exact heat is not specified but we can make a fairly good guess that it was far too high once we see that after the third step where the oil is pressed out that the solid oil cake comes out between 120°C and 130°C, this is after a trip through a long corkscrew and certainly a few minutes of waiting in the press for enough stuff to accumulate where it certainly cooled a bit. Based on this we can safely assume that the oil came dangerously close to, if not above its smoke point just when it was being extracted, and it is important to remember that oil doesn't have to get all the way up to its smoke point before it starts to oxidize, I looked at studies where researchers got soybean oil to oxedize at temperatures as low as 90°C. Soybean oil is compromised just through the process of extracting it. If we look deeper into the oil production process we see that there are several more points in that process where the oil is heated and given opportunity to oxidize, and by the time it is bottled it is almost certainly rancid and unsafe for consumption. And it is important to remember that this is not unique to soybean oil, this happens to nearly every edible oil on the grocery store shelf.
But what are the specific risks of soybean oil? Soybean oil is notably high in omega-6 polyunsaturated fatty acids and a diet high in omega-6s has been linked to diseases like nonalcoholic fatty liver disease, cardiovascular disease, obesity, inflammatory bowel disease, rheumatoid arthritis, and Alzheimer's disease.  Soybean oil is dangerous and feeding large amounts of it to people frankly is unethical. We should not eat it and we should seek to avoid it whenever we can along with nearly every other contemporary oil.
It is important to remember that prior to the early 1900s, with the exception of places like the Philippines, everyone on the planet cooked with animal fats like butter, lard, ghee, and tallow, Filipinos, because they didn't have the same access to livestock, used coconut oil which is the only plant based oil high in saturated fat (fats solid at room temperature) making it just as safe and stable for cooking as animal fats. The transition from animal fat to processed oils was by far the biggest dietary shift in the history of mankind and it has undoubtably brought the world terrible health challenges more severe and widespread than ever before. We should never cook with anything other than animal fats or coconut oil, olive oil dates back to biblical times and is safe to eat in moderation as long as we don't eat it, the same can be said of avocado oil which of course comes from an oily fruit the Aztecs began cultivating over five thousand years ago. All other oils should be avoided, soybean oil of course being the worst of these. Be sure to check the ingredients of the products you buy, you will of course have to pay a bit more for avocado oil based mayonnaise but, as you live a life free from ingesting industrial waste like soybean oil, you will find yourself much healthier and spending much less time and money at doctors' offices. The health of you and your family should be one of your biggest priorities.