Out of all the things I've done to try to improve my health over the past decade, removing vegetable/seed oils from my diet has had the most positive effect. These oils are nasty and my body dislikes them so much. If I am accidentally exposed to them, it triggers a migraine and brain fog. Too much of them, and I can actually feel it in my joints for several days after consumption.
I highly recommend avoiding canola oil, cotton seed oil, corn oil, safflower oil, sunflower oil, soybean oil, and grapeseed oil at all costs. You may have seen a bottle of one of these oils on store shelves spouting health claims [*insert eye roll here*]. Contrary to what these companies are allowed to claim, they are NOT heart healthy. Consuming them will do you no favors.
Soybean oil is the most commonly used oils out of the seven I listed above. It's cheap to process and easy to get. Most soybean oil used comes from genetically modified soy crop. A recent study found that consuming soybean oil actually has the power to rewire your brain DNA and has a possible link to Autism, Alzheimer's, anxiety, and depression. Not to mention, soybean oil also has the power to fatten us up and contribute to metabolic disorders and chronic inflammation. Kudos to the soybean lobbyists for keeping this info hidden from the general public. If you knew this oil was linked to the things above, would you have consumed it? Some common sources of soybean oil include fried fast foods, overly processed packaged junk foods, and popular plant-based meat substitutes (can we all just agree that eating real meat is far better for us already?).
Other vegetable/seed oils don't show the same link to the above conditions. However, that doesn't mean a link has yet to be found. These oils can oxidize easily and go rancid. I truly believe they are the real culprits in atherosclerosis and other cardiovascular conditions. They are hidden in almost every conventionally produced packaged food in the world, and they are kind of hard to avoid.
Scientists in the early 20th century discovered that we could hydrogenate seed oils (namely cottonseed), which allowed for them to be used to extend the shelf-life of certain foods. The hydrogenation process turns the liquid oils into solid fats that are more stable and last longer. "Coincidentally", once these oils (both in their liquid and hydrogenated form) were introduced to the masses via packaged foods, the rates of many diseases skyrocketed. And you know what got blamed? Saturated fat. Saturated fats have been around for millennia and humans have been consuming them for just as long. Our bodies are adapted to them. But seed oils have only been around for a blink of an eye when we look at human history. There are studies that actually show that when saturated fats are replaced by seed oil sludge, health suffers and death rates increase.
The reason why we see "health" claims on bottles of these garbage oils is because they do tend to lower cholesterol. And the American Heart Association thinks that's a good thing. Canola oil is marketed as a cholesterol free health food. But it's not healthy. Canola oil, along with other seed oils, can release toxic byproducts in the bloodstream. You become what you eat, and if you're eating seed oils, you are jeopardizing the integrity of your cell membranes. Seed oils are high in omega 6, and consuming too much of them shifts our omega-6 to omega-3 ratios way out of balance. Too much omega-6 can put our bodies into a pro-inflammatory state and lead to chronic inflammation, which has been linked with every chronic disease that humans suffer from.
I could go on and on about the dangers of these oils. But, to make a long post short, I just want to emphasize the importance of eating real food. Seed oils may be marketed as real food, but they are not. If you've got time, I urge you to go on You Tube and watch How Canola Oil is Made. Other seed oils are made in the same heavily processed way. Better options include avocado and olive oil. Some people do well with coconut oil (I don't). And butter and other animal fats are always an option as well. McDonalds original fry recipe called for cooking them in beef tallow before the tallow was deemed "deadly" and replaced with soybean oil in the late 1980s. Other fast food chains and processed food companies made similar switches around this same time. We also saw an increase in pro-inflammatory chronic conditions at this time. Coincidence? You tell me...