Processed Seed Oils

Industrial seed oils — canola/rapeseed, soybean, corn, sunflower, safflower, cottonseed, grapeseed — are extracted by mechanical pressing and solvent extraction, then refined, bleached, and deodorized. They're cheap, neutral-tasting, and have high smoke points, which is why they dominate restaurant cooking, processed food, baked goods, and most "vegetable oil" labels.

The argument against seed oils centers on two points: they're high in omega-6 linoleic acid (which a vocal subset of researchers argue is pro-inflammatory at modern intake levels), and they're a marker of ultra-processed food consumption. Mainstream nutrition bodies (AHA, Harvard, EFSA) currently consider unsaturated seed oils preferable to saturated fats for cardiovascular health, citing decades of trial and epidemiological data.

What the evidence actually shows

On omega-6: most studies don't find that higher linoleic acid intake increases markers of systemic inflammation in humans, despite the biochemical reasoning. On oxidation: seed oils can oxidize when reheated repeatedly at high temperatures (typical commercial deep-frying scenarios), and oxidized lipids may have adverse effects. On cardiovascular outcomes: replacing saturated fat with polyunsaturated fat (including seed oils) is associated with lower CVD events in long-term trials. The honest summary is that the trial evidence supports them at typical home-cooking exposures, while concerns are sharper for ultra-processed food and repeatedly-heated commercial frying oil.

Practical guidance

The biggest exposure to seed oils for most people isn't home cooking — it's ultra-processed snacks, restaurant fryers, and packaged foods. Cooking at home with olive oil, avocado oil, butter, or ghee for most things is a reasonable default. Using a seed oil occasionally for high-heat cooking is unlikely to be problematic. Cutting ultra-processed food does more to lower seed-oil intake than fussing over the oil bottle at home.