The mechanistic case against seed oils
Seed oils such as soybean, corn, and sunflower are high in linoleic acid, an omega-6 polyunsaturated fat. Critics point to two mechanisms: polyunsaturated fats oxidize readily under heat and storage, forming reactive aldehydes and other breakdown products, and a high omega-6 intake can shift the substrate pool toward arachidonic-acid-derived signaling. Both mechanisms are biochemically real.
What human trials show, and where the argument is unsettled
When tested as replacements for saturated fat, these oils generally lower LDL-C and have neutral-to-favorable effects on most cardiometabolic markers in controlled trials and large cohorts. The mechanistic concerns about oxidation and omega-6 signaling have not consistently translated into worse hard outcomes in that evidence.
The honest summary is a genuine tension: plausible mechanisms on one side, broadly reassuring trial and cohort data on the other, complicated by the fact that seed oils are concentrated in ultra-processed foods that carry their own confounders. This diagram presents both sides rather than declaring a verdict. General educational information, not dietary advice; individual decisions should involve a qualified professional.