Seed Oils
Seed oils have become one of the most polarising topics in the nutrition world, especially on social media. There's alarmist messaging suggesting that they are inflammatory toxins, they damage the gut, they disrupt hormones and they drive weight gain. On the other side are those arguing that seed oils are safe, and that the demonisation is based on misunderstanding, cherry-picked studies, or oversimplifying complex science.
The picture is more nuanced. Whilst seed oils are not health-promoting powerhouses, the evidence does not support the claims that they are significantly harmful or inflammatory. This guide breaks down the seed oil controversy clearly: what the claims are, where they come from, what the science actually says, and what’s genuinely worth paying attention to.
The seed oil claims
On the whole the messaging surrounding seed oils is negative with an emphasis being put on how they cause chronic inflammation in the body, promote weight gain, disrupt hormones, contain dangerous toxins produced dueing processing, are driving the obesity and disease epidemics and damage the gut lining.
There are some more positive claims, albeit less common, which centre around the polyunsaturated fat content supporting cholesterol levels and heart health.
These claims come from both misunderstandings and real research - but often applied out of context.
Where do these claims come from?
The seed oil controversy originates from legitimate nutrition science exploring the omega-6 to omega-3 ratio. Early hypotheses suggested that excessive omega-6 intake (and relatively low omega-3 intake) promoted inflammation. This hypothesis has been weaponized by diet culture and supplement companies promoting oils such as olive oil and coconut oil as superior. The controversy has also been amplified by anti-processed-food movements, which reasonably critique ultra-processed foods, but often incorrectly attribute harm specifically to seed oils rather than to ultra-processing in general.
There are reasonable conversations to have about balance, processing and quality, but most online claims dramatically overstate the impact of seed oils alone.
What does the evidence say?
Omega-6 fats are not inherently inflammatory. And this is the crux of the controversy. For decades, omega-6 fatty acids (particularly linoleic acid, found abundantly in seed oils) were thoguht to promote system inflammation. However, controlled trials have not supported this mechanism. Recent evidence even suggests that omega-6 fatty acids may even generate anti-inflammatory compounds like lipoxins. And another study found that higher levels of linolieic acid were linked to lower levels of inflammation, not higher. Although more high-quality research is needed, it does appear unlikely that a high intake of omega-6 from seed oils will elevate mortality or disease risk.
Another area that has been discussed is the omega-6 to omega-3 ratio. A more favourable ratio is associated with better health outcomes. But that does not mean that omega-6 is harmful. Instead it means that inadeuate omega-3 is problematic.
The processing is another argument given by those demonising seed oils. Seed oils undergo processing including extraction, refining, bleaching and deodorisation. These processes do generate some oxidised compounds. But the real concern is not seed oils specifically, but ultra processed foods in general, which often containe refined carbohydrates, added sugars and excessive salt, alongside seed oils.
Finally is the topic of heat. When heated too high temperatures, seed oils can generate oxidised fatty acid derivatives. But this is true of all fats, including butter and olive oil. The magnitude of harm from dietary oxidised compounds, in the context of overall antioxidant intake, is unclear.
Can seed oils form part of a balanced diet?
Seed oils can be part of a balanced diet, particularly when they are used as part of whole-food preparation (such as in salad dressings or sauteed vegetables). Cold-pressed seed oils can be a way to further mitigate any inflammatory risk. But importantly, seed oils are more affordable and demonising them creates unnecessary expense and psychological burden. Balancing the cost with nutrition is important, and for many people they're simply a neutral background fat that doesn't noticeably influence symptoms.
When should I be cautious with seed oils?
Seed oils are ubiquitous in ultra-processed foods. The harm in these foods likely derives from the entire ultra-processed food profile, not specifically from seed oils. So the theoretical oxidative stress from seed oil consumption is going to be most relevant in those with a high ultra-processed, low antioxidant dietary intake. If you are eating a diet abundant in whole vegetables, fruits, nuts and seeds, then the antioxidant load of your diet will far exceed any oxidative burden from seed oils.
If you have a severe inflammatory condition (such as Crohn's, ulcerative colitis or rheumatoid arthritis) then you may benefit from increasing omega-3 fats, and moderating omega-6 ones. But this can done through focusing on anti-inflammatory foods in the diet alognside reducing intake of ultra-processed ones.
So what oils should I use?
Fixating on seed oil elimination delays addressing actual inflammatory drivers, inadequate protein intake, excessive refined carbohydrates, poor gut health and hormonal dysregulation.
Someone eating a diet abundant in whole vegetables and using a seed oil-based dressing is supporting inflammation reduction more than another person eating 'seed-oil-free' ultra-processed foods packed full of excess salt and refined sugars.
So rather than fixating on the oils, support inflammation by increasing
your intake of fatty fish (salmon, mackeral, sardines, herring and anchovies), flax and chia seeds and walnuts
antioxidant rich foods, found in whole vegetables and fruits
home cooked, minimally processed foods
And alongside this, reduce your intake of refined carbohydrates, added sugars and ultra-processed foods.
This matters far more than eliminating any one type of fat.
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