Are seed oils actually bad for you?

The claim that seed oils such as soybean, canola, sunflower, and corn oil are uniquely harmful has spread widely online, and it is not supported by the weight of evidence. Systematic reviews and the positions of the American Heart Association, the World Health Organization, and comparable bodies hold that replacing saturated fats with polyunsaturated vegetable oils reduces cardiovascular events. The primary mechanistic argument against them concerns omega-6 linoleic acid supposedly driving inflammation, but controlled trials measuring inflammatory markers in humans have generally not found that effect, and observational data associate higher linoleic acid levels with lower rather than higher cardiovascular risk.

Two nuances keep this from being a simple dismissal. The ratio of omega-6 to omega-3 in modern Western diets has shifted substantially, and there is a legitimate argument for increasing omega-3 intake from fish and other sources, which is different from claiming omega-6 is toxic. And heating any oil past its smoke point repeatedly, as in commercial deep frying, degrades it and produces compounds worth avoiding, which is a case against reused fryer oil rather than against the oil itself. The more defensible version of the concern is confounding: seed oils are abundant in ultra-processed foods, and the health problems associated with those diets are more plausibly attributable to the overall dietary pattern, calorie density, and processing than to the oil in isolation. Cooking at home with olive, canola, or avocado oil is not a health risk on current evidence.