I used to keep my kitchen counter looking like a nutrition label from the nineteen fifties. No margarine, no shortening, butter only. Then someone told me coconut oil was the real villain, and I swapped it out for olive oil. A few months later, seed oils became the enemy, and suddenly even my salad dressing needed a fact-check.
It’s exhausting, isn’t it? There seems to always be a new nutritional bad guy — first carbs, then fat, then carbs again, and now seed oils are center stage. You’ve probably seen the claims: they’re inflammatory, they cause disease, you should avoid them completely. But what does the actual evidence say?
What Are Seed Oils, Exactly?
The term usually refers to vegetable oils like sunflower oil, soybean oil, and canola oil — ones that are higher in polyunsaturated fats than in saturated fat. They’re everywhere: in store-bought bread, restaurant stir-fries, the dressing you grab without reading the label on a Tuesday evening.
And they’re not going anywhere anytime soon.
What Does the Evidence Actually Say?
A recent umbrella review looked at 48 systematic reviews and meta-analyses. Forty-eight. It examined how vegetable oils affect blood pressure, blood lipids, blood sugar, body weight, cardiovascular disease, and cancer.
Here’s what it found.
Oils rich in monounsaturated and polyunsaturated fats — which includes many seed oils — generally improved or at least maintained healthy lipid profiles when compared to more saturated fats. Canola oil lowered total cholesterol and LDL while having neutral effects on triglycerides and VLDL (very-low-density lipoprotein, one of the particles that carries fat in your blood). Rice bran oil did something similar.
Virgin or extra-virgin olive oil — which I reach for almost every morning — lowered total cholesterol, sometimes reduced LDL, and often raised HDL. On the other hand, coconut oil and palm oil consistently raised both total cholesterol and LDL, though they also tended to raise HDL, which complicates the picture a bit.
When it comes to blood pressure and blood sugar control, some seed oils actually showed benefits. Flaxseed oil produced small but meaningful reductions in blood pressure — especially diastolic pressure — possibly because of its high ALA content (alpha-linolenic acid, a plant-based omega-3 fatty acid). Sesame oil showed modest blood pressure improvements and better fasting glucose and HbA1c levels (a marker of average blood sugar over the past few months) in some studies. Even olive oil and coconut oil produced small improvements in certain glycaemic markers.
For inflammation, cardiovascular events, and cancer, data were limited but did not suggest increased risk from seed oils. The same held true for body weight and body composition — only very small changes showed up in a few studies.
The Fine Print
It’s worth noting that the overall certainty of evidence was mostly low. And we don’t eat oils in isolation — they’re part of meals, cooking methods, whole diets. Oils used at home differ from those repeatedly reheated in fast-food restaurant fryers, and that matters.
But regardless, the current evidence does not support the idea that consuming seed oils as part of a healthy diet leads to harmful health outcomes. In some cases, they may even offer small improvements.
The Bottom Line
This is one of those topics where the internet and science don’t quite agree on volume. The headlines scream danger. The data whispers something more nuanced.
Managing your overall energy intake and aiming for mostly whole foods — that’s what matters most. Whether you include some seed oils in your diet or choose to skip them is unlikely to make a huge difference to your health, as long as the rest of your plate looks good.
Eighty-twenty is enough here too.
The Morning Reset
This week: grab a glass of water and one piece of fruit for breakfast. Read just the first ingredient on your coffee creamer or yogurt — no need to audit the whole label. Small shifts, big difference.
Frequently Asked Questions
Are seed oils inflammatory?
The umbrella review found limited data on inflammation, but the existing evidence did not suggest increased risk from seed oil consumption. The idea that they are inherently highly inflammatory is more popular online than it is in the research.
Is olive oil better than seed oils?
Virgin and extra-virgin olive oil showed solid benefits for cholesterol, including raising HDL. But many seed oils also improved lipid profiles compared to more saturated fats. Neither is a villain — both can fit into a healthy diet.
Should I avoid seed oils in restaurant food?
The evidence doesn’t single out seed oils as harmful. What does matter is overall diet quality. Restaurant oils are often repeatedly reheated, which changes their properties — but that’s a cooking practice issue, not specifically a seed oil problem.
A note from Hazel: I still reach for olive oil most mornings. It tastes good on toast, and it makes me feel like the kitchen is a calm place. But if I’m making a quick stir-fry with canola oil, I don’t stress about it anymore. The evidence gave me permission to let go — and honestly, that’s worth just as much.