What counts as a seed oil?
The term usually refers to oils extracted from seeds, including canola, corn, soybean, sunflower, safflower, grapeseed, and cottonseed oil. These oils contain different proportions of monounsaturated and polyunsaturated fats, including the essential omega-6 fatty acid linoleic acid.
Do omega-6 fats cause inflammation?
The concern is often that linoleic acid can be converted into signaling molecules involved in inflammation. Human evidence does not support the conclusion that normal dietary intake of omega-6 fats broadly increases inflammation. The American Heart Association reports that replacing saturated fat with polyunsaturated fat lowers LDL cholesterol and can reduce cardiovascular events.
Where the concern is reasonable
Oils can degrade when repeatedly heated, stored poorly, or allowed to become rancid. Deep-fried and ultra-processed foods can also be easy to overconsume. In those cases, the larger issue is the processing method, repeated high heat, total calorie intake, and overall food pattern, not simply the fact that an oil came from a seed.
Practical guidance
- Build meals around vegetables, fruit, whole grains, legumes, minimally processed proteins, and appropriate portions.
- Use liquid oils rich in unsaturated fats in place of butter, lard, shortening, and other fats high in saturated fat when appropriate.
- Do not repeatedly reuse frying oil.
- Discard oil that smells or tastes rancid.
- Choose an oil suited to the cooking temperature and flavor you want.
Clinical bottom line
Most people do not need to eliminate seed oils. It is more useful to evaluate the entire diet and replace heavily processed foods with nutrient-dense options. Olive, canola, avocado, soybean, sunflower, and other unsaturated oils can all fit into a healthy eating pattern.