Are seed and vegetable oils “toxic”?!
From viral TikTok videos to popular book charts, vegetable oils—commonly known as “seed oils”—are a hot subject at the moment. To be honest, the discussion around the value of vegetable oils has been ongoing since their introduction to the market.
Recently, with the rise of the carnivore diet, criticism of vegetable oils has surged back into social media circles. You might have seen posts labeling these cooking oils as “toxic sludge,” “motor oil,” “the hateful eight,” and “the foremost cause of chronic illness that nobody is aware of.”
The rationale against vegetable oils typically goes like this… Animal fats have been consumed by humans for millennia. In contrast, vegetable fats were developed in the last century as profit-driven companies sought to create cheap-to-produce products for gullible buyers.
Another point raised: Like margarine, vegetable oils were promoted as healthier substitutes for butter, yet critics claim these oils are worse than butter, increasing the likelihood of obesity, anxiety, depression, ulcerative colitis, and more.
Conversely, other specialists argue that vegetable oils are safe, potentially even beneficial to health—and significantly better than butter.
So, who holds the truth?
As with many nutritional discussions, the reality is too complex to be distilled into a meme.
In this article, we will help you differentiate between scientific facts and pseudoscience so you can make knowledgeable choices regarding the oils you decide to use in your meals.
What are vegetable oils?
Commonly referred to as “seed oils,” vegetable oils originate, as you may guess, from the seeds of plants. The most frequently found in a regular grocery store include:
- Canola oil
- Corn oil
- Safflower oil
- Sesame oil
- Sunflower oil
- Soybean oil
- Grapeseed oil
Just so you know, if you think there are many oils absent from that listing, it’s likely that those oils come from non-seed sources (like olive, avocado, palm, or coconut oil, all of which derive from fruits and aren’t classified as vegetable or seed oils).
How are vegetable oils processed?
Oils that aren’t classified as vegetable oils—such as olive and avocado oil—are sourced from inherently fatty foods. In fact, olives are so rich in oil that technically you could create your own olive oil at home. (Just search “how to make olive oil from scratch,” and you’ll find numerous videos guiding you through the process.)
The same cannot be said for most vegetable oils, which primarily come from foods with a noticeably lower fat content to start with.
For instance: A cup of green olives contains around 20 grams of fat,1 whereas a cup of corn contains just 2 grams.2
Consequently, producers need to implement an elaborate multi-step technique to extract this minimal quantity of oil from these low-fat foods. These steps include:
- Crushing: A machine exerts high pressure to extract oil from the seeds.
- Refining: The seeds are heated with a solvent, like hexane, to retrieve more oil.
- Deodorizing: To achieve a neutral flavor and eliminate undesirable compounds, the extracted oil is then heated at 400 F (204 C) for several hours.
Throughout this method, beneficial polyphenols and other stabilizing nutrients are lost, and small quantities of unsaturated fats are converted into trans fatty acids (also known as partially hydrogenated fats).
(Fun fact: This transformation also occurs during deep frying. When vegetable oils fry in a restaurant deep fryer for extended periods, the trans fat content of the oil rises.)
Describing these processed oils as “toxic” could be an overstatement. Nonetheless, nutrition scientists generally agree that trans fats should be limited in the diet, and in 2018, the Food and Drug Administration prohibited producers from incorporating trans fats into processed foods.3 4