[zenon]

Trans fat from partially hydrogenated vegetable oil is (mostly) Elaidic acid, which is probably harmful. Butter contains other trans fats, like Vaccenic acid. We don't know much about the long-term health effects of Vaccenic acid.

[Xdafjgneoiwe]

"Published data suggest that all fatty acids with a double bond in the trans configuration raise the ratio of plasma LDL to HDL cholesterol."

https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2830458/