Seed oils have become one of the most controversial topics in nutrition.
Depending on who you listen to, they’re either harmless cooking staples or the root cause of inflammation, weight gain, and chronic disease. Social media has been especially loud on this, often without context or nuance.
So what does the science actually say about seed oils and inflammation?
Let’s separate evidence from exaggeration.
What Are Seed Oils?
Seed oils are vegetable oils extracted from the seeds of plants. Common examples include:
- Sunflower oil
- Canola (rapeseed) oil
- Soybean oil
- Corn oil
- Grapeseed oil
They’re widely used in cooking, packaged foods, and restaurants because they’re affordable and have a neutral flavour.
Why Are Seed Oils Linked to Inflammation?
Most concerns centre around one thing: omega-6 fatty acids.
Seed oils tend to be high in omega-6 fats, which play a role in inflammatory pathways in the body. This has led to the belief that eating seed oils automatically causes chronic inflammation.
But this is where nuance matters.
Omega-6 Fats
Omega-6 fatty acids are essential fats, meaning your body needs them and cannot produce them on its own.
Research shows that omega-6 fats do not inherently cause inflammation and instead, they can actually help reduce bad cholesterol. It’s also shown that replacing saturated fat with omega-6 fats is associated with improved heart health.
Large human studies do not show higher inflammation markers in people who consume omega-6-rich oils as part of a balanced diet.
What About the Omega-6 to Omega-3 Ratio?
This is where things often get misunderstood.
It’s true that many modern diets are:
- High in omega-6
- Low in omega-3
The solution isn’t eliminating seed oils, it’s increasing omega-3 intake.
Foods rich in omega-3s include:
- Oily fish (salmon, sardines, mackerel)
- Flaxseeds and chia seeds
- Walnuts
Improving this balance matters more than cutting out seed oils entirely.
Do Seed Oils Become “Toxic” When Heated?
Another common claim is that seed oils oxidise easily and become harmful when heated.
In reality:
- Most commonly used seed oils are refined to be heat-stable
- They’re widely used in cooking and food manufacturing with safety standards
- Oxidation risk increases mainly with repeated overheating or deep frying
This is not unique to seed oils - all fats can degrade under extreme heat.
Ultra-Processed Foods
When people associate seed oils with inflammation, they’re often noticing something else.
Seed oils are commonly found in:
- Ultra-processed snacks
- Fast food
- Sugary baked goods
These foods are high in:
- Refined carbohydrates
- Added sugars
- Excess calories
It’s the overall diet, not seed oils alone, that contributes most to inflammation.
What Does Research Actually Say?
When looking at well-designed human studies:
- Seed oils are not independently linked to chronic inflammation
- Replacing saturated fat with polyunsaturated fats improves cardiovascular markers
- Inflammatory markers often decrease, not increase
Animal cell studies are frequently misused online, but they don’t reflect real-world human diets.
Should You Avoid Seed Oils?
For most people, there’s no strong scientific reason to eliminate seed oils completely.
Some top tips:
- Use a variety of fats (olive oil, seed oils, nuts, seeds)
- Focus on wholefoods
- Increase omega-3 intake
- Limit ultra-processed foods overall
Nutrition doesn’t need extremes to be effective.
What Diso Says
Seed oils are not the inflammatory villains that they’re often made out to be.
Current human evidence does not support the claim that seed oils cause chronic inflammation when consumed as part of a balanced diet.
Instead of fearing individual ingredients, focus on dietary patterns that support your long-term health.
Use the information you learn going forward to build a diet that’s healthy, balanced and, most importantly, sustainable. Oh, and if you need a little extra encouragement or advice on your health journey, our supplement guides are always here to lend a hand and help build up your wellbeing knowledge!
