Lecithin was first identified in 1846 by Maurice Gobley, a French chemist. It is the name for a mixture of phospholipids, an important component of food products, occurring both naturally and added as a supplement. The body breaks down this mix into choline, phosphate, glycerol, and fatty acids.
Found naturally in a number of foods, people can consume lecithin in egg yolks, fish, grains, legumes, peanuts, soybeans, wheat germ, and yeast. It is also used in food preparation to create products such as baked goods, chocolate, margarine, and mayonnaise because of its ability to moisturize, preserve, and emulsify. It is a key ingredient in cooking spray, the substance used to replace oils, margarine, and butter in sautéing and baking.
Lecithin is also used in medical practice as well as in other commercial products, such as plastics, pharmaceuticals, pesticides, cosmetics, soap, and paints. For these applications, it is extracted from eggs or soybeans. It is also sold in powder, grain, liquid, or capsules as a dietary supplement.
As a dietary supplement, lecithin is claimed to have a number of roles, including improving cardiovascular health, relieving the symptoms of arthritis, and improving liver function. It is primarily offered as a supplement to assist in weight loss and to provide boosts in fat metabolism, despite the fact that these claims are made without the presentation of any scientific evidence to show that lecithin is effective in weight loss and fat metabolism. Additionally, some claims have been made to suggest that phospholipids from soy improve the metabolism of cholesterol, although the studies that supported this have had their methodology called into question.
Despite this, lecithin does have a crucial role in the human body, as evidenced by the fact that approximately 30% of the brain's weight and 66% of liver fat is made of this substance. In addition, it is an essential constituent of every human cell. The American Heart Association believes that lecithin is best obtained naturally through foodstuffs, rather than through supplements, and no Recommended Daily Allowance (RDA) has been set by the US Food and Drug Administration (FDA).
Doses of over 25 grams per day of lecithin can cause negative side effects, including nausea, stomach upset, diarrhea, and vomiting. It can also be dangerous to a very small portion of the population with an extreme soy allergy. Although most of these people are allergic only to soy protein, and therefore not affected by soy lecithin, people who are extremely allergic may be sensitive all soy products and experience an allergic reaction.