Are Seed Oils Bad for You?
Seed oils have become one of the most debated topics in nutrition. Depending on who you follow online, they are either a harmless part of everyday cooking or a hidden cause of chronic disease. The truth, as usual, is more measured than either extreme. Here is what seed oils actually are, what the science says, and how to make informed choices.
What Are Seed Oils?
Seed oils are cooking oils extracted from the seeds of plants. The most common ones you will encounter in UK food are:
- Sunflower oil — from sunflower seeds, one of the most widely used cooking oils in the UK
- Rapeseed oil — from rapeseed (also called canola oil in North America), the UK’s most popular everyday cooking oil
- Soybean oil — from soybeans, heavily used in processed foods and restaurant cooking
- Corn oil — from maize kernels, common in frying and baking
- Cottonseed oil — from cotton plant seeds, found in some processed snacks
- Sesame oil — from sesame seeds, used in Asian cooking
- Grapeseed oil — from grape seeds, a byproduct of winemaking
How seed oils are made
Modern seed oils are typically produced through a process of mechanical pressing followed by solvent extraction (usually with hexane), then refining, bleaching, and deodorising. This is the process that concerns some critics — they argue it is heavily industrialised and involves chemicals. In reality, the refining process removes impurities, free fatty acids, and any trace solvent residues. The finished product meets strict food safety standards. Cold-pressed versions of some seed oils (like rapeseed) are also available and skip the solvent extraction step.
The omega-6 question
The main nutritional point of contention is the omega-6 to omega-3 ratio. Most seed oils are high in linoleic acid, an omega-6 polyunsaturated fatty acid. Some researchers have hypothesised that a high omega-6 to omega-3 ratio in the modern Western diet could promote inflammation. However, as we will cover below, the clinical evidence for this is far less clear-cut than social media suggests.
The Viral Claims vs the Science
The anti-seed-oil movement has gained enormous traction on social media, particularly on TikTok, X (formerly Twitter), and YouTube. Here are the main claims and what the evidence actually shows.
Claim: “Seed oils cause chronic inflammation”
This is the foundational claim of the movement. The argument is that omega-6 fatty acids (particularly linoleic acid) are converted into pro-inflammatory compounds in the body, driving conditions like heart disease, diabetes, and autoimmune disorders.
What the science says: A 2025 review by the Genetic Literacy Project, which examined multiple randomised controlled trials, found that linoleic acid does not increase markers of chronic inflammation or chronic disease risk in humans. The metabolic pathway from linoleic acid to inflammatory compounds exists, but the body tightly regulates this conversion. Eating more linoleic acid does not simply produce more inflammation in a linear way. Heart UK states that replacing saturated fats with polyunsaturated fats (including those from seed oils) is associated with reduced cardiovascular risk.
Claim: “Seed oils oxidise and become toxic when heated”
The argument is that polyunsaturated fats are unstable and break down into harmful aldehydes and other oxidation products during cooking.
What the science says: It is true that polyunsaturated oils are less heat-stable than saturated fats or monounsaturated oils like olive oil. However, refined seed oils have had many of the compounds that accelerate oxidation removed during processing. For normal home cooking temperatures, standard refined sunflower or rapeseed oil is perfectly safe. Deep-frying at very high temperatures for prolonged periods does produce more oxidation products, but this applies to any oil and is a reason to avoid heavily reused frying oil — not a reason to avoid seed oils specifically. The British Nutrition Foundation advises using oils within their smoke point and not reusing cooking oil excessively.
Claim: “Our ancestors never ate seed oils”
The evolutionary argument suggests that because industrial seed oils only became common in the 20th century, our bodies are not adapted to them.
What the science says: This is an appeal to nature. Our ancestors also did not eat refined sugar, pasteurised milk, or modern wheat varieties. The fact that a food is new does not make it harmful. What matters is the biochemical effect, and the clinical trials on linoleic acid consumption do not support the claim that it causes harm at typical dietary levels. The NHS and EFSA both include seed oils in their dietary guidance as appropriate sources of unsaturated fat.
Claim: “The rise in seed oil consumption tracks with the rise in obesity and chronic disease”
This is a correlation argument — seed oil consumption increased over the 20th century, and so did rates of obesity, heart disease, and diabetes.
What the science says: Correlation does not equal causation. Over the same period, consumption of sugar, processed food, and total calories also increased dramatically, while physical activity decreased. Attributing the rise in chronic disease to one specific dietary component, when dozens of variables changed simultaneously, is not scientifically valid. The British Nutrition Foundation notes that overall dietary patterns and calorie balance are far more significant than any single ingredient.
Which Seed Oils Are in UK Food?
Seed oils are extremely common in UK food manufacturing. Here is a guide to the main ones, where you will find them, and their omega-6 content.
| Oil | Common Products | Omega-6 Content | Notes |
|---|---|---|---|
| Sunflower oil | Crisps, biscuits, mayonnaise, ready meals | ~65% | The most common seed oil in UK processed food |
| Rapeseed oil | Cooking oil, margarine, salad dressings | ~20% | Better omega-6:3 ratio; NHS-recommended |
| Soybean oil | Fast food, restaurant frying, processed snacks | ~50% | Often listed as “vegetable oil” |
| Corn oil | Margarine, frying oil, baked goods | ~55% | Less common in UK retail; more in food service |
| Cottonseed oil | Some crisps, snack foods, cheap frying oil | ~50% | Less common in UK than US |
| Sesame oil | Asian ready meals, stir-fry sauces, dressings | ~40% | Usually used in small amounts for flavour |
| Grapeseed oil | Some dressings, premium cooking sprays | ~70% | Highest omega-6 of common seed oils |
On UK food labels, seed oils are often listed generically as “vegetable oil” followed by the specific source in brackets — for example, “vegetable oil (sunflower)” or “vegetable oil (rapeseed, palm).” UK labelling regulations require manufacturers to identify the specific plant source, so you can always check.
How to Check for Seed Oils in Your Food
If you want to monitor or reduce your seed oil intake, here is how to do it practically.
Read the ingredients list
Look for terms like “sunflower oil,” “rapeseed oil,” “soybean oil,” “corn oil,” or the catch-all “vegetable oil.” Under UK food labelling rules, the specific oil must be named in brackets after “vegetable oil,” so you will always know which oil is used.
Use NutraSafe’s ingredient scanner
Scan any product barcode with the NutraSafe app and the full ingredient list is broken down for you instantly. You can see exactly which oils are used, along with any additives, allergens, or other ingredients you might want to track. No need to squint at tiny label text in the supermarket aisle.
Check restaurant and takeaway menus
Restaurants and takeaways are not required to list specific oils on menus, but most chip shops and fast-food chains use sunflower oil or a vegetable oil blend for frying. If it matters to you, ask — staff can usually tell you which oil is used in the fryer.
Know the alternatives
If you prefer to cook with non-seed oils at home, the most common alternatives are extra virgin olive oil (for dressings, medium-heat cooking), butter or ghee (for baking, frying), coconut oil (for high-heat cooking, though high in saturated fat), and avocado oil (for high-heat cooking with a neutral flavour).
The key takeaway
The dose makes the poison. Seed oils consumed in moderation as part of a balanced diet are considered safe by the NHS, the British Nutrition Foundation, Heart UK, and EFSA. The viral claims about seed oils causing widespread chronic disease are not supported by the weight of clinical evidence. If you want to reduce them, that is a perfectly reasonable personal choice — but it is not a medical necessity. Either way, reading labels and knowing what is in your food is always a good idea.
Know What’s in Your Food
Scan any product to see exactly which oils, additives, and ingredients are inside. Make informed choices with confidence.
Download NutraSafe FreeFrequently Asked Questions
Are seed oils banned anywhere?
No country has banned seed oils. They are approved for use in food across the UK, EU, US, and virtually every nation. Some social media influencers have claimed that seed oils are “banned in Europe,” but this is false. What some EU countries have restricted are specific trans fats (which can be created during partial hydrogenation of any oil, including seed oils), not seed oils themselves. The UK, EU, and US all permit and widely use sunflower oil, rapeseed oil, soybean oil, and other seed oils in food manufacturing.
Is rapeseed oil a seed oil?
Yes, rapeseed oil (also known as canola oil in North America) is a seed oil — it is extracted from the seeds of the rapeseed plant. However, rapeseed oil is often singled out as one of the “better” seed oils because it has a relatively favourable fatty acid profile: it is low in saturated fat, high in monounsaturated fat (similar to olive oil), and has a better omega-6 to omega-3 ratio than most other seed oils. The NHS and British Nutrition Foundation both recommend rapeseed oil as a healthy cooking oil.
What can I use instead of seed oils?
If you prefer to reduce your seed oil intake, common alternatives include extra virgin olive oil (widely regarded as the gold standard for health), butter or ghee (higher in saturated fat, so best used in moderation), coconut oil (also high in saturated fat), and avocado oil. For everyday UK cooking, the NHS recommends using small amounts of unsaturated oils such as olive oil, rapeseed oil, or sunflower oil. The key is moderation and variety rather than eliminating any single oil entirely.
Do seed oils cause inflammation?
This is the central claim of the anti-seed-oil movement, but the clinical evidence does not support it. A 2025 review by the Genetic Literacy Project, examining multiple randomised controlled trials, found that linoleic acid (the main omega-6 fatty acid in seed oils) does not increase markers of inflammation in humans. Heart UK and the British Nutrition Foundation both state that replacing saturated fats with unsaturated fats from sources including seed oils is associated with improved cardiovascular health, not increased inflammation.
Are seed oils the same as vegetable oil?
In practice, yes — most “vegetable oil” sold in UK supermarkets is a seed oil, typically rapeseed oil or a blend of rapeseed and sunflower oil. The term “vegetable oil” is a generic label that can refer to any plant-derived oil, but in UK food manufacturing it almost always means one or more seed oils. If a product ingredient list says “vegetable oil,” you can check the specific oil in brackets — UK labelling rules require manufacturers to identify the specific plant source, such as “vegetable oil (rapeseed)” or “vegetable oil (sunflower, palm).”
Related Reading
Last updated: February 2026. Sources: NHS, British Nutrition Foundation, Heart UK, EFSA, Genetic Literacy Project (2025).