There are so many internet personalities who try to throw their credentials around and say, “Oh if you believe seed oils are bad for you, then you’re just uneducated.” This is a great way to silence dissent about widely accepted ideas regarding health and science. For years we heard that replacing butter with polyunsaturated fats would reduce your risk of heart disease. I still distinctly remember spraying “I can’t believe it’s not butter” on my popcorn when I was younger. As someone who is close to finishing their third year of nutrition studies, I am here to disagree with this claim.
People like to point to outcome trials as evidence of anything, but they are never able to isolate seed oils as a factor long term. And they adjust numbers to make seed oils seem healthier than they are to the public. For instance, one study claims a “19% reduction” in cardiovascular events, but that’s actually relative risk reduction. That means the actual number is about… 1%. And since we aren’t controlling for everything else they are eating in their diet, a 1% reduction over 4–5 years means nothing. This is just one example but there are many more, the vast majority of “nutrition science” is completely bunk.
You’ve probably heard “correlation doesn’t equal causation”, but nutrition science is exclusively associative. This is because we can only study populations and trends, we cannot lock someone in a room and control their diets for months/years. This is our biggest limitation in the field of nutrition research, and the reason why mechanistic data matters. We can clearly demonstrate numerous mechanisms of harms regarding high seed oil intake using basic biochemistry.
Seed oils are high in omega-6 polyunsaturated fats, which aren’t inherently bad in themselves, but they are chemically unstable. Under heat, processing, exposure to air, or light, they are prone to oxidation. This is a similar process to what turns iron into rust. This is due to their numerous carbon double bonds in the fatty acids carbon chain. Oxidation creates lipid peroxides, which introduce reactive oxygen species into our bodies. These are essentially unstable molecules with unbound electrons. This process increases oxidative stress in the body, especially if antioxidant intake does not match. Oxidative stress is positively associated with systemic inflammation, which is the primary driver of conditions like heart disease, diabetes, and neurodegenerative disorders. Oxidation products, without enough antioxidants, raise systemic inflammation in the body and contribute to chronic diseases and cancer.
As important as it is to minimize your intake of these oils, there are a few things to consider. The first thing is sourcing. Deep fried foods are always going to be the WORST offender by far. The same oil is essentially being boiled all day, introducing a cascade of toxic oxidation products into the oil. The second thing to consider is that junk food is still junk food, even if it isn’t made with seed oils. I see a trend of people incorporating “beef tallow chips” and the like into their daily diet because they are better. Better does not mean good, they are still micronutrient-less carbs that aren’t designed to satiate you, but make you more hungry. The third thing is that eating whole foods with seed oils is still better than eating junk food without them. When I got to college I was extremely upset that the cafeteria only served protein cooked in canola oil. So I resorted to less nutritious options and paid the price. (Haagen daaz doesn’t have seed oils teehee).
Cutting seed oils out of your diet has massive health benefits though, not just long term disease prevention, but short term benefit as well. Oxidized seed oils are very pro-inflammatory, this can manifest as acne or pain all around your body. For instance, I noticed a decrease (basically complete remission) of my tendonitis upon cutting out seed oils. Another amazing benefit of them out is reduced sun burning. Due to omega-6’s highly oxidized and compromised composition, it is very reactive in the sun. Replacing them with stable saturated fats improved my sun tolerance greatly.
I could keep talking about seed oils forever, but I will leave you with an important take away. Polyunsaturated fats, especially from artificial sources, are terrible for you. Monounsaturated fats, olive or avocado oil, are better. And saturated fat from butter, tallow, ghee, coconut oil, etc is BEST.
If you would like to hear more, I post daily on Instagram “@theseedoilbro”