Hi,
You've probably seen this claim doing the rounds:
"Seed oils are poisoning you. Throw out everything in your kitchen."
Like most viral nutrition takes, there's a grain of truth buried inside a lot of noise. Here's what the science actually says — and what I actually do.
P.S. I'm taking on 5 men who want to lose 15 pounds or more on a free 12-week fat loss coaching programme. If that's you, just hit reply and let me know.
WHAT ARE SEED OILS?
Seed oils are vegetable oils extracted from seeds — sunflower, canola, soybean, corn, grapeseed, safflower. They're high in polyunsaturated fatty acids (PUFAs), particularly omega-6 linoleic acid.
They're also in virtually everything — used heavily in ultra-processed foods, fast food, and most restaurant cooking because they're cheap and have a high smoke point.
That last part matters, and we'll come back to it.
WHAT THE SCIENCE ACTUALLY SHOWS
The main argument against seed oils is that linoleic acid converts to arachidonic acid, which triggers inflammation. It sounds logical. The research doesn't back it up.
A 2025 study analysing blood markers from nearly 1,900 people found that higher linoleic acid levels were associated with lower inflammation and better cardiometabolic health. A separate systematic review across 36 human studies found that increasing dietary linoleic acid by up to 551% did not significantly raise arachidonic acid in the blood.
The cardiovascular data is similar: linoleic acid is consistently linked to lower risk of heart disease, stroke, and type 2 diabetes. This is the current consensus from institutions including Johns Hopkins and Memorial Sloan Kettering.
Seed oils, consumed normally, are not the villain they're made out to be.
WHERE THE CONCERN IS LEGITIMATE
Polyunsaturated fats are chemically unstable under heat. When seed oils are cooked at high temperatures — especially repeatedly, as in commercial deep-frying — they oxidise and produce toxic compounds called aldehydes, including 4-HNE and acrolein. At high levels these are linked to oxidative stress, cancer risk, and neurodegenerative conditions.
The concern isn't seed oil in a home-cooked meal. It's seed oils heated to 180–200°C, repeatedly, in a commercial fryer — which is exactly how they're used in most fast food and ultra-processed snacks.
Real mechanism. Wrong context in most of the online discourse.
THE MYTH: "SEED OILS ARE POISONING YOU"
Ultra-processed foods — which happen to be loaded with seed oils, refined carbs, sugar, and artificial ingredients — are strongly associated with poor health. Blaming the oil alone is like blaming the packaging.
Dietary pattern matters far more than any single ingredient. If you're overweight and not yet exercising consistently, stressing over which oil is in your pan is the wrong battle. Get the basics right first — calories, protein, movement, sleep. That will move the needle far more than optimising your cooking fat.
WHAT I ACTUALLY DO
Personally, I cook almost exclusively with olive oil — it covers about 99% of what I do in the kitchen. For anything genuinely high heat, I use avocado oil, which has one of the highest smoke points of any cooking fat and stays stable under heat.
That's it. No seed oils at home — not because I think they're toxic, but because I don't need them when olive and avocado oil cover everything I cook.
If you want a simple rule: olive oil for most cooking, avocado oil when you need high heat. Worry less about what oil you're using and more about what you're cooking in it.
See you next week,
Gabriel Nutrition Coach & Founder | gbMeals | Nutrition Hacks