Social media has recently made your common old kitchen cooking oil a controversial choice – Expert Karen Geary looks at both sides
Against my better judgment, I’ve decided to enter the seed oil debate! If you’ve missed it so far, it’s been a hot online topic recently, attracting some extreme views from varioous experts. But nutrition is rarely black and white, and studies can be found to support almost any argument!
Last month, Professor Sarah Berry, the chief scientist at ZOE Ltd, shared her views on seed oils on a Zoe podcast, and rebuttals quickly followed. Rather than diving into the rather complex science, here’s a quick layman’s take on both sides (feel free to skip to the end if you just want my take and some practical advice!).
What are seed oils?
Seed oils are vegetable oils extracted from the seeds of plants such as rapeseed, soybean, sunflower, safflower and corn. They have been widely used since the rise of ultra-processed foods in the late 20th century. Some claim they support heart health, while others argue they are the equivalent of dietary demons and deeply harmful. Is there a clear verdict?
The case for …
Good for your heart
Mainstream nutrition bodies are fans of seed oils due to their high polyunsaturated fat (PUFA) content, particularly omega-6. Studies suggest replacing saturated fats with PUFAs lowers “bad” cholesterol, a key marker for heart disease risk.
Professor Berry emphasises that studies don’t consistently show omega-6 intake as pro-inflammatory: while they can contribute to inflammation, they also generate anti-inflammatory mediators. Some research even suggests increased PUFA intake correlates with a lower risk of cardiovascular disease.
Essential fatty acids
Seed oils provide linoleic acid, an essential omega-6 fat the body cannot make. Rather than eliminating omega-6, Professor Berry suggests ensuring enough omega-3 (from flaxseeds, walnuts, and omega-3 supplements) in order to maintain balance.
Affordability and versatility
Seed oils are cheap, widely available and have a high smoke point, making them convenient for cooking.
Processing and stability
Berry also notes that refining simply removes impurities rather than introducing harmful substances.
However, some oils degrade at high temperatures, forming oxidation by-products, so choosing the right oil for the right cooking method matters.
The Case Against …
The Omega-6 to Omega-3 imbalance
Critics like Dr. Zoë Harcombe argue that modern diets contain excessive omega-6 due to seed oil prevalence in processed foods. Historically, omega-6 and omega-3 were consumed in balance, but today’s intake skews toward omega-6, which some link to chronic inflammation, a driver of heart disease and obesity.
Oxidation and processing
Refined seed oils undergo high heat and chemical treatments. Critics argue this process alters their structure, leading to oxidation by-products like aldehydes – linked to stress and aging. The refining process often includes colour modification and deodorisation due to rancidity.
Questionable data
Nutritional epidemiology relies on self-reported dietary data, which can be inaccurate. Critics point out that factors such as genetics and lifestyle can make it difficult to reach clear conclusions.
Industry influence
Some compare the current seed oils argument to the old trans fats debate: once marketed as healthy but later linked to disease. They argue industry influence could be unduly shaping public recommendations. Seed oils are cheap, have high smoke points, and are widely used in processed foods, making them the most profitable to use by lareg manufacturers.
Refined vs. Cold-Pressed
Not all seed oils are equal!
Refined seed oils are processed with heat and solvents, leading to oxidation risks and nutrient loss. These are the ones common in cheap ultra-processed foods.
Cold-pressed (unrefined) oils are extracted mechanically at lower temperatures, preserving nutrients and antioxidants. But this comes with a shorter shelf life – these are best for dressings or low-heat cooking.
If you want to minimise risk, opt for cold-pressed, unrefined oils when possible. For high-heat cooking, the better plant-based options include avocado oil or coconut oil (which have smoke points of 230-270°C). If you eat animal products, ghee (clarified butter), lard or tallow also work in moderation (smoke points 180-250°C).
So, what’s the verdict?
The simple answer is – there’s no simple answer! While mainstream bodies support seed oils for cholesterol reduction (a debate in itself), critics raise concerns about oxidation, inflammation, and industry bias. Since seed oils are in many ultra-processed foods, their effects can be hard to isolate. For a balanced approach in your own diet, my personal advice is:
Prioritise whole-food fats – choose nuts, seeds, avocado and olives over processed oils.
Use minimally processed oils – extra virgin olive oil and avocado oil have lower oxidation risks. Olive oil is fine for gentle cooking (~190°C), while butter is best for low-heat cooking (~150°C).
Balance your omegas: get your omega-3 from flaxseeds, walnuts and oily fish like sardines, mackerel, and salmon.
Be mindful of processed foods as many contain refined seed oils.
Opt for cold-pressed oils in dressings (and sparingly, due to their cost!).
What Do I Do?
I cook with avocado oil, ghee and olive oil. For dressings I use extra virgin olive oil for its health benefits. Very occasionally I use cold-pressed oils like sesame, walnut and flaxseed in a dressing. I eat butter, not spreads, because I prefer to know what’s in it.
And yes, I enjoy chips when dining out (they are usually fried in sunflower) – without guilt! But I do notice some after-effects.
Seed oils are neither saints nor villains – their impact depends on your overall diet quality, their processing and balance with other fats.
If you want to dig deeper, the fully referenced links below provide both arguments.
• Dr. Sarah Berry (pro-seed oil perspective)
• Dr. Zoë Harcombe (critical perspective)
