Lecithin is the most abundant of the phospholipids. It is a fatty food substance, which serves as a structural material for every cell in the body. It is an essential constituent of the human brain and nervous system. It forms 30 per cent of the dry weight of the brain and 17 per cent of the nervous system.

Lecithin is also an important component of the endocrine glands and the muscles of the heart and kidneys. It makes up 73 per cent of the total liver fat. Nervous, mental or glandular overactivity can consume lecithin faster than its replacement. This may render a person irritable and exhausted. It is, therefore, of utmost importance to add lecithin to the diet, if the body's own supply decreases as in old age or working under stress.

Lecithin is derived from the Greek Word, likithos, meaning egg yolk. Egg yolk is a rich source of lecithin, and also a rich source of cholesterol. This combination makes it possible for the lecithin to emulsify the cholesterol. Vegetable oils, whole grain cereals, soyabeans, liver and milk are other rich sources of lecithin. The cells of the body are also capable of synthesizing it as needed, if several of the B vitamins are present. Since these B vitamins are generally removed when grains are refined, people who eat exclusively white flour products are lacking them.