Lecithin is a fatlike substance called a phospholipid it is produced daily by the liver if the diet is adequate it is needed by every cell in the body and is a key building block of cell membranes without it they would harden lecithin protects cells from oxidation and largely comprises the protective sheaths surrounding the brain it is composed mostly of b vitamins phosphoric acid choline linoleic acid and inositol although it is a fatty substance it is also a fat emulsifier hence it