Seed oils have become one of the most polarising topics in nutrition. We cut through the noise with an evidence-based look at the data on linoleic acid, oxidation, and aging.
Few nutrition debates generate more heat than seed oils. On one side, proponents of seed oil avoidance — often aligned with carnivore or ancestral eating communities — argue that industrial vegetable oils are a primary driver of modern disease and accelerated aging. On the other side, mainstream nutrition science and most cardiologists continue to recommend replacing saturated fat with polyunsaturated fats, including those in seed oils, to reduce cardiovascular risk. The truth, as usual, is considerably more nuanced than either extreme suggests, and disentangling genuine science from motivated reasoning on both sides requires careful attention to what the research actually shows.
"Seed oils" is a colloquial term for industrially extracted oils from seeds or grains: soybean oil, canola (rapeseed) oil, corn oil, sunflower oil, safflower oil, cottonseed oil, and rice bran oil. These oils are predominantly rich in polyunsaturated fatty acids (PUFAs), particularly omega-6 fatty acids — primarily linoleic acid (LA).
These oils are industrially extracted through a process that typically involves pressing and solvent extraction (usually hexane), followed by degumming, bleaching, and deodorisation at high temperatures. This process is different from cold-pressing, which is how olive oil and avocado oil are often produced. Critics argue that the industrial extraction process itself generates oxidation products and contaminants; proponents note that the final refined oils, while lacking the polyphenols present in cold-pressed oils, have low residual solvent levels and are generally considered safe by regulatory agencies.
Seed oils are distinct from several other commonly used fats:
The anti-seed oil argument rests on several interconnected claims, each with different levels of scientific support: