As nouns the difference between lecithin and sphingomyelin
is that
lecithin is (organic chemistry) the principal phospholipid in animals; it is particularly abundant in egg yolks, and is extracted commercially from soy it is a major constituent of cell membranes, and is commonly used as a food additive (as an emulsifier) while
sphingomyelin is (biochemistry) a phospholipid, derived from sphingosine and choline, found in nerve tissue.