Vaccenic acid is a naturally occurring Trans fat and an omega-7 fatty acid. It is the predominant kind of trans-fatty acid found in human milk, in the fat of , and in such as milk, butter, and yogurt.[ Vaccenic acid was discovered in 1928 in and butter.
Mammals convert it into rumenic acid, a conjugated linoleic acid,]
Cow milk had highest trans-vaccenic acid content in the first few days of milking.
Its IUPAC name is (11 E)-11-octadecenoic acid, and its lipid shorthand name is 18:1 trans-11. The name was derived from the Latin vacca (cow).
