Lecithin is an extremely important ingredient of body cell membranes, which regulate the entry and exit of nutrients and other substances. Lecithin is largely composed of choline (a B complex vitamin), and contains linoleic fatty acid, phosphorus and inositol. Although clearly a fatty substance, it behaves like an emulsifier and helps the elimination of fat. Its active ingredient is phospatidylcholine.

Food sources of lecithin are brewer's yeast, egg yolk, fish, grains, legumes, soy, and wheat germ Most supplementary lecithin is derived from soy or fresh egg yolk.

Supplements may be important for elderly people with reduced absorption powers, as they help prevent arteriosclerosis and cardiovascular disease, they assist the absorption of vitamin B1 (thiamine) by the liver and vitamin A by the intestine, they enhance brain activity, and help to repair liver damage from alcoholism. Lecithin is useful for strengthening the immune system, the nervous system, and for maintaining a healthy liver.

Persons lacking calcium, with calcium malabsorption disorders, or osteoporosis, should not take lecithin supplements without consulting experienced health care practitioners.