If you follow the natural health world on social media, you may have noticed that seed oils have become the latest nutritional villains. You can hardly move online without coming across a video where some Influencer argues that seed oils are poison and US Health Secretary Robert F Kennedy Jr has called them “toxic” and vowed to act against them. Sunflower, rapeseed, soybean and other seed oils are being blamed for everything from inflammation and obesity to heart disease.
I’ve been following this debate with interest, and I have to say I find some of the claims rather puzzling. After all, seeds and their oils have been part of healthy diets for generations, and many contain ‘essential’ fatty acids that our bodies actually need.
So where has this sudden hostility towards seed oils come from, and are there any reliable facts behind it?
These theories are rooted in concerns about industrial food processing and the growing interest in ancestral diets, and traditional foods. Supporters argue that modern refined vegetable oils are a relatively recent addition to our diets and may be contributing to chronic disease.
One of the main concerns centres on omega-6 fatty acids, particularly linoleic acid, which is found in many seed oils. The argument is that consuming too much omega-6 encourages inflammation in the body, especially when our intake of omega-3 is relatively low.
There is some biochemical reasoning behind this theory, but the human research tells a different story. Studies generally haven’t found that eating more seed-oil based linoleic acid increases inflammatory markers, and Omega-6 is actually an essential fatty acid, meaning we need it for normal health. Many nutritious wholefoods, including sunflower seeds, walnuts and sesame seeds naturally contain Omega 6.
Rather than trying to eliminate omega-6, I think we’d be better off concentrating on getting more omega-3, which many of us don’t consume regularly. This means eating things like oily fish, tinned sardines, or taking a fish oil or cod liver oil supplement.
The debate becomes particularly interesting when we consider if we’re blaming seed oils for the problems with ultra-processed foods. Seed oils are used extensively in ultra-processed foods – for example in cooking crisps, biscuits, pastries, cakes, ready meals and takeaway foods. But they’re rarely the only ingredient we should be questioning.
Many of these products also contain substantial amounts of refined starches, added sugars and salt, and are designed to be inexpensive, convenient and highly palatable.
We now have substantial evidence linking diets high in ultra-processed foods with obesity, type 2 diabetes, cardiovascular disease and poorer metabolic health. These dietary patterns can also contribute to chronic low-grade inflammation. But is it really the seed oil that’s causing the problem?
Imagine someone decides to eliminate seed oils from their diet. They stop eating crisps, biscuits, takeaway chips, processed snacks and commercial cakes. Instead, they start cooking more meals from scratch and eating more wholefoods.
They feel better, perhaps lose weight and notice improvements in their energy. It’s tempting to conclude that removing seed oils was responsible, but they’ve also dramatically improved the overall quality of their diet – it seems like that might be the bigger change!
One of the things that particularly bothers me about the anti-seed-oil movement is that it lumps together oils that can be quite different in how they’re made and their nutritional benefits.
Take rapeseed oil and canola oil, for example. When you buy a good-quality, cold-pressed rapeseed oil, it also retains its natural colour and flavour, along with beneficial compounds such as vitamin E. It’s naturally low in saturated fat, rich in healthy monounsaturated fats, and contains omega-3 as well as Omega 6 and Omega 9.
Canola oil comes from the same plant and is widely used in food processing. It’s usually highly refined, which removes these natural compounds and gives it a more neutral flavour.
I don’t think it’s correct to lump organic, cold pressed rapeseed oil with highly processed canola oil – they are as different as apples and oranges.
Two seed oils I particularly love from a nutritional perspective are flaxseed and hempseed.
Flaxseed oil (also called linseed oil) is exceptionally rich in the plant omega-3 fatty acid ALA, which contributes to maintaining normal blood cholesterol levels and is important for normal cellular function.
It’s a wonderful addition to a salad dressing, smoothie or drizzled over cooked vegetables. Because it’s delicate and easily oxidised, it should be kept refrigerated and never used for frying.
Whole or ground flaxseeds are also excellent, providing all the healthy fibre and lignans that aren’t present in the oil.
Hempseed oil is another incredibly healthy option, containing both omega-6 and omega-3 essential fatty acids. It also contains smaller amounts of gamma-linolenic acid (GLA), a fatty acid involved in the body’s inflammatory signalling pathways.
With its delicious nutty flavour, hempseed oil is perfect for dressings, dips and drizzling over soups. Like flaxseed oil, it’s best used cold.
One concern about seed oils that does deserve attention is what happens when they’re repeatedly heated. This would particularly apply to commercial chips and fried snacks like crisps. Polyunsaturated fats are vulnerable to oxidation, and prolonged high-temperature cooking, particularly repeated deep-frying, can produce potentially harmful breakdown compounds.
But there’s a world of difference between using a quality oil in your own kitchen and eating food cooked in a highly refined oil that’s been repeatedly heated in a commercial fryer. For everyday cooking, cold pressed sunflower seed oils and good-quality rapeseed oil are both excellent options. Flaxseed and hempseed oils are best kept for cold dishes.
Having said that – many ‘vegetable’ oils for sale in supermarkets are made from seed oils that are highly processed, not cold pressed or organic. Personally I avoid cooking with those oils – oils like that CAN contain harmful compounds. If I was choosing between extra virgin olive oil and a generic processed ‘vegetable’ oil I will choose the olive oil every time.
I think the anti-seed-oil movement has raised some really worthwhile questions about the ingredients used in industrial food production and the quality of the fats we consume. These are definitely worth reflecting on. But it has also created a lot of totally unnecessary fear around foods that can be important parts of a healthy diet.
My advice is to focus on the bigger picture. Eat fewer ultra-processed foods, choose good-quality oils, include more omega-3-rich foods and enjoy a variety of fats in moderation. And don’t always trust what you hear on Instagram!
