Essential fatty acid

Essential fatty acids, or EFAs, are fatty acids that humans and other animals must eat. The body needs them for good health but cannot make them.
Only two fatty acids are needed for humans. When the two EFAs were discovered in 1923, they were called "vitamin F", but in 1929, research on rats showed that the two EFAs are fats rather than vitamins.
Some other fatty acids are "conditionally essential", meaning that they may become essential under some circumstances.