HeraSphere #44: Seed Oils Aren't the Problem

Hi friends,

I'm at the beach this week. I packed my good olive oil for salads but left my avocado oil at home. So when it came time to cook, the only other option in the rental kitchen was a big bottle of canola oil sitting in the cabinet.

And I just stood there. Do I use it? Or do I drive to the store for avocado oil like a health nut mom and risk my kids making fun of me?

That little standoff with a canola bottle sent me down a rabbit hole. I'd absorbed a rule I had never actually checked: seed oils bad, fancy oils good. So I went and read the research, and what I found is more useful than either side of the internet is telling you.

The TL;DR

• The oxidation that matters happens in the bottle and the deep fryer, not in your bloodstream. Human trials keep showing that linoleic acid, the omega-6 fat in seed oils, does not raise oxidative stress or inflammation in your body.

• The real problem isn't the oil, it's what the oil is carrying. Most of the seed oil people eat comes packed inside ultra-processed food, and that's the actual health driver.

• Stability is the smart reason to pick a cooking oil, not omega-6 content. This is where the "use olive oil and avocado oil" crowd happens to be right, just for the wrong stated reason.

• The 1:1 omega-6 to omega-3 ratio target has almost no good evidence behind it. Eating more omega-3 matters far more than fearing omega-6.

• You do not need to throw out your canola. I'll give you a cheat sheet for what to use when.

What everyone is saying about oil

• The case against seed oils is that they're industrially extracted, high in omega-6, relatively new to the human diet, and that their rise tracks with the rise in chronic disease. Dr. Mark Hyman, on the Huberman Lab podcast, makes the cleanest version of this argument: he'd rather eat whole-food fats like olive oil, avocado, and nuts than an industrially manufactured product, and he points out that most seed oil intake is hidden inside processed food.

• The mainstream nutrition science lands somewhere differently. Researchers at Johns Hopkins and a wave of 2025 reviews find that swapping saturated fat for the polyunsaturated fat in seed oils actually lowers cardiovascular risk, and that linoleic acid does not raise oxidative stress in the human body.

• Both sides are mostly arguing past each other. The scientists are talking about what happens inside your body, while the influencers are mostly right about the food system and mostly wrong about the salad dressing.

What oxidative stress actually is, and where it really happens

• Oxidation is fat reacting with oxygen, light, and heat, which creates unstable byproducts. Picture a cut apple turning brown on the counter, or a bag of nuts going rancid in the pantry. That's oxidation you can see and taste.

• Oxidation in the bottle, from light and air and time, and oxidation in a deep fryer running hot oil for hours, is real. Oxidation inside your body, from eating normal amounts of these oils, is the thing that randomized trials keep failing to find. As one review put it, humans are not a bottle of seed oil sitting on a shelf.

• The fats in seed oils are polyunsaturated, which is a chemist's way of saying they have lots of fragile bonds that break down faster under high heat. Olive and avocado oil are mostly monounsaturated, which means fewer of those fragile spots and more stability in the pan. That difference is the real reason to think about which oil you reach for, and it has nothing to do with omega-6 being toxic.

• Buy small dark bottles, store them cool, and don't reuse frying oil. That handles the large majority of the actual oxidation risk.

The omega-6 ratio myth

• The most repeated anti-seed-oil claim is about ratios. The argument goes that ancestral diets had roughly equal omega-6 and omega-3, modern diets are flooded with omega-6, and we should aim to get back to 1:1.

• The evidence doesn't bear that out. When Johns Hopkins researchers studied linoleic acid and heart disease, the protective association held whether people had high or low omega-3 levels. Their advice was to stop obsessing over the ratio and focus on the actual foods.

• Add omega-3 rather than subtracting omega-6. More fatty fish and walnuts does more for you than fearing one half of a ratio that turns out not to predict much.

Match the oil to the job

The honest rule is to match the oil to the method, not rank oils by a single number.

• I always believed the famous "never cook with olive oil, the smoke point is too low" rule. However, that is a myth. Smoke point is just the temperature where an oil starts to visibly smoke and break down. Extra virgin olive oil sits around 375°F, which sounds low, but stability in the pan matters more than that number, and olive oil is one of the most stable oils you can heat. It's mostly monounsaturated fat, plus it carries polyphenols, the natural plant compounds that also happen to protect the oil as it cooks.

• For raw and finishing, use extra virgin olive oil. Dressings, drizzles, and dips are where its polyphenols stay fully intact and its cardiovascular data is strongest.

• For everyday cooking, olive oil still wins. Sautéing, roasting, and shallow pan-frying sit well within its comfort zone, low-smoke-point fears notwithstanding. Avocado oil is the other strong everyday pick.

• For genuine high heat, reach for avocado oil, ghee, or light olive oil. Searing and stir-frying are the one place to skip raw extra virgin olive oil, since you'd cook off the polyphenols you paid for.

• For deep frying, the method is the problem more than the oil. Repeatedly reheated oil of any kind is where the real oxidation byproducts form, which makes this a how-often-you-eat-out question more than a home-kitchen one.

Your seven-oil cheat sheet

• Extra virgin olive oil is your default. Mostly monounsaturated with lots of polyphenols, it has the strongest cardiovascular evidence of any oil and works from raw all the way up to medium-high cooking.

• Avocado oil is your high-heat pick. Very stable and great for searing, though fakes are common, so buy reputable brands.

• Canola is far better than its reputation. It's low in saturated fat and high in omega-3, and the highest plant-oil intake was linked to 16% lower total mortality in a large 2025 study. This is the one I used at the beach, with a clear conscience.

• Sunflower oil is fine in moderation. High in omega-6 with a high smoke point, and the high-oleic versions hold up better for occasional high-heat cooking.

• Corn oil isn't harmful, but it's a marker. Nutritionally unremarkable, it mostly shows up inside fried and processed food, which is the part worth watching.

• Ghee is a stable, heat-friendly flavor pick. It takes high heat well, but it's saturated fat, so treat it as a flavor choice rather than a health food.

• Butter is fine in moderation. Lovely for flavor at low to medium heat, though the highest butter intake was tied to 15% higher mortality compared with plant oils in that same study.

• Coconut oil is popular but oversold. It's heat-stable and tastes great, but it's very high in saturated fat and raises LDL cholesterol in a lot of people, which makes it a sometimes-oil.

What to actually do

• Cook at home with stable fats and make olive oil your default. It covers nearly everything you do in a normal kitchen.

• Cut ultra-processed food, since that's the real lever. The seed oil that matters is the kind you never measured, eaten inside something that came in a wrapper.

• Eat more omega-3 and stop counting ratios. Fish, walnuts, and yes, canola.

• Don't panic over a restaurant meal. One fried dinner out isn't what shapes your health. The pattern is.

So here's where I landed after my standoff with that canola bottle. I used it, cooked with it all week, and made my salads with the good olive oil I'd bothered to pack. The thing I'd quietly believed, that there are good oils and bad oils and you can tell which is which by how expensive or natural they sound, was the part that didn't survive the research. What I now will consider is how often we eat food fried in oil we never see.

Cooking with what I’ve got,

Lilly

PS: If you have a friend who threw out her canola in a panic, or who feels guilty every time she cooks with anything that isn't avocado oil, forward this to her. She can stop worrying about the wrong thing.

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Note: While I love diving deep into research and sharing what I've learned about women's health and wellness, I want to be crystal clear: I'm a passionate health advocate and researcher, not a medical professional. Think of me as your well-informed friend who does extensive homework – but not your doctor.

Everything I share in HeraSphere comes from careful research and personal experience, but it's meant to inform and inspire, not to diagnose or treat any medical conditions. Your body is uniquely yours, and what works for one person might not work for another. Always consult your healthcare provider before making significant changes to your diet, exercise routine, or wellness practices, especially if you have underlying health conditions or take medications.

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