Essential fatty acids (EFAs) are responsible for the structure of all cell membranes; helping with the regulation of cholesterol metabolism and provide the basis for hormone production. There are two EFAs: linoleic and alpha-linolenic acids, which are particularly important to the growing foetus and in early infancy for normal brain development. Polyunsaturated fats are categorised as omegas: 3, 6, 7 and 9. They yield EFAs, and the omega 3 derivatives, eicosapentaenoic acid (EPA) and docosahexanoic acid (DHA). Sources of EFAs include evening primrose oil, fish oils and flax seed oil.