A 12-week randomized controlled trial in 52 healthy adults found that a high-linoleic acid (LA) diet (10% energy) significantly reduced EPA, ETA, and some DPA levels compared with a low-LA diet, despite equal ALA intake. Higher LA intake increased the omega-6:omega-3 ratio, ARA:EPA ratio, and ARA-/EPA-derived oxylipins, shifting lipid mediators toward a more pro-inflammatory omega-6-dominant profile, with implications for populations consuming ultra-processed foods high in vegetable oils.