All cells throughout the human body are enveloped by membrane composed chiefly of essential fatty acids in the form of compounds known as "phospholipids." The major phospholipid of the human body is phosphatidylcholine. Commercially available phosphatidylcholine preparations are derived from soy lecithin. These preparations are used in the treatment of Alzheimer's disease, bipolar depression, elevated cholesterol levels, and liver disorders. The beneficial effects are likely due primarily to the essential fatty acid components of phosphatidylcholine and lecithin preparations.