Lecithin is a generic term to designate any group of yellow-brownish fatty substances occurring in animal and plant tissues composed of phosphoric acid, choline, fatty acids, glycerol, glycolipids, triglycerides, and phospholipids (e.g., phosphatidylcholine, phosphatidylethanolamine, and phosphatidylinositol).
Lecithin was first isolated in 1846 by the French chemist and pharmacist Theodore Gobley. In 1850 he named the phosphatidylcholine léchithine. Gobley originally isolated lecithin from egg yolk—λέκιθος (lekithos) is 'egg yolk' in ancient Greek—and established the complete chemical formula of phosphatidylcholine in 1874; in between, he had demonstrated the presence of lecithin in a variety of biological matters, including venous blood, bile, human brain tissue, fish eggs, fish roe, and chicken and sheep brain.
Lecithin can easily be extracted chemically (using hexane, ethanol, acetone, petroleum ether, benzene, etc.) or mechanically. It is usually available from sources such as soy beans, eggs, milk, marine sources, rapeseed, cottonseed, and sunflower. It has low solubility in water, but is an excellent emulsifier. In aqueous solution, its phospholipids can form either liposomes, bilayer sheets, micelles, or lamellar structures, depending on hydration and temperature. This results in a type of surfactant that usually is classified as amphipathic. Lecithin is sold as a food supplement and for medical uses. In cooking, it is sometimes used as an emulsifier and to prevent sticking, for example in nonstick cooking spray.
Phosphatidylcholine occurs in all cellular organisms, being one of the major components of the phospholipid portion of the cell membrane.
Commercial lecithin, as used by food manufacturers, is a mixture of phospholipids in oil. The lecithin can be obtained by degumming the extracted oil of seeds. It is a mixture of various phospholipids, and the composition depends on the origin of the lecithin. A major source of lecithin is soybean oil. Because of the EU requirement to declare additions of allergens in foods, in addition to regulations regarding genetically modified crops, a gradual shift to other sources of lecithin (e.g., sunflower oil) is taking place. The main phospholipids in lecithin from soya and sunflower are phosphatidyl choline, phosphatidyl inositol, phosphatidyl ethanolamine, and phosphatidic acid. They often are abbreviated to PC, PI, PE, and PA, respectively. Purified phospholipids are produced by companies commercially.
Hydrolysed lecithin 
To modify the performance of lecithin to make it suitable for the product to which it is added, it may be hydrolysed enzymatically. In hydrolysed lecithins, a portion of the phospholipids have one fatty acid removed by phospholipase. Such phospholipids are called lysophospholipids. The most commonly used phospholipase is phospholipase A2, which removes the fatty acid at the C2 position of glycerol. Lecithins may also be modified by a process called fractionation. During this process, lecithin is mixed with an alcohol, usually ethanol. Some phospholipids, such as phosphatidylcholine, have good solubility in ethanol, whereas most other phospholipids do not dissolve well in ethanol. The ethanol is separated from the lecithin sludge, after which the ethanol is removed by evaporation to obtain a phosphatidylcholine-enriched lecithin fraction.
Properties and applications 
Lecithin has emulsification and lubricant properties, and is a surfactant. It can be totally metabolized (see Inositol) by humans, so is well tolerated by humans and nontoxic when ingested; some emulsifiers can only be excreted via the kidneys.
Lecithin is used for applications in human food, animal feed, pharmaceuticals, paints, and other industrial applications.
- In the pharmaceutical industry, it acts as a wetting, stabilizing agent and a choline enrichment carrier, helps in emulsifications and encapsulation, and is a good dispersing agent. It can be used in manufacture of intravenous fat infusions and for therapeutic use.
- In animal feed, it enriches fat and protein and improves pelletization.
- In the paint industry, it forms protective coatings for surfaces with painting and printing ink, has antioxidant properties, helps as a rust inhibitor, is a colour-intensifying agent, catalyst, conditioning aid modifier, and dispersing aid; it is a good stabilizing and suspending agent, emulsifier, and wetting agent, helps in maintaining uniform mixture of several pigments, helps in grinding of metal oxide pigments, is a spreading and mixing aid, prevents hard settling of pigments, eliminates foam in water-based paints, and helps in fast dispersion of latex-based paints.
- Lecithin also may be used as a release agent for plastics, an antisludge additive in motor lubricants, an antigumming agent in gasoline, and an emulsifier, spreading agent, and antioxidant in textile, rubber, and other industries.
Use with foods 
In confectionery, it reduces viscosity, replaces more expensive ingredients, controls sugar crystallization and the flow properties of chocolate, helps in the homogeneous mixing of ingredients, improves shelf life for some products, and can be used as a coating. In emulsions and fat spreads it stabilizes emulsions, reduces spattering during frying, improves texture of spreads and flavour release. In doughs and bakery it reduces fat and egg requirements, helps even distribution of ingredients in dough, stabilizes fermentation, increases volume, protects yeast cells in dough when frozen, and acts as a releasing agent to prevent sticking and simplify cleaning. It improves wetting properties of hydrophilic powders (e.g., low-fat proteins) and lipophilic powders (e.g., cocoa powder), controls dust, and helps complete dispersion in water. Lecithin is the emulsifier that keeps cocoa and cocoa butter in a candy bar from separating. It can be used as a component of cooking sprays to prevent sticking and as a releasing agent. In margarines, especially those containing high levels of fat (>75%), lecithin is added as an 'antispattering' agent for shallow frying.
Lecithin is approved by the United States Food and Drug Administration for human consumption with the status "generally recognized as safe." Lecithin is admitted by the EU as a food additive, designated by E number E322. Research studies show soy-derived lecithin has significant effects on lowering serum cholesterol and triglycerides, while increasing HDL ("good cholesterol") levels in the blood of rats.
Compatibility with special diets 
A proven benefit and suggested use for lecithin is for those taking niacin to treat high cholesterol. Niacin treatment can deplete choline, necessitating an increased amount of lecithin or choline in the diet.
Egg-derived lecithin is not usually a concern for those allergic to eggs since commercially available Egg Lecithin is highly purified and devoid of allergy causing egg proteins. Egg lecithin is not a concern for those on low-cholesterol diets, because the lecithin found in eggs markedly inhibits the absorption of the cholesterol contained in eggs.
Genetic Modification 
As described above, lecithin is highly processed. Therefore, genetically modified (GM) protein or DNA from the original GM crop from which it is derived often is undetectable - in other words, it is not substantially different from lecithin derived from non-GM crops. Nonetheless, consumer concerns about genetically modified food have extended to highly purified derivatives from GM food, such as lecithin. This concern led to policy and regulatory changes in Europe in 2000, when Regulation (EC) 50/2000 was passed which required labelling of food containing additives derived from GMOs, including lecithin. Because it is nearly impossible to detect the origin of derivatives such as lecithin, the European regulations require those who wish to sell lecithin in Europe to use a meticulous system of Identity preservation (IP). 
Religious restrictions 
Soy-derived lecithin is considered by some to be kitniyot and prohibited on Passover for Ashkenazi Jews when many grain-based foods are forbidden, but not at other times. This does not necessarily affect Sephardi Jews, who do not have the same restrictions on rice and kitniyot during Pesach/Passover.
Muslims are not forbidden to eat lecithin per se; however, since it may be derived from animal as well as plant sources, care must be taken to ensure this source is halal. Lecithin derived from plants and egg yolks is permissible, as is that derived from animals slaughtered according to the rules of dhabihah.
- Gobley (1846) "Recherches chimiques sur le jaune d'œuf" (Chemical researches on egg yolk), Journal de Pharmacie et de Chemie, series 3, vol. 9, pages 81-91; on page 84, Gobley gives the proceedure by which he extracted and characterized lecithin.
- Gobley (1850) Recherches chemiques sur les œufs de carpe (Chemical researches on carp eggs), Journal de Pharmacie et de Chemie, series 3, vol. 17, pages 401-430; see especially page 411: "Je propose de donner au premier le nom de Léchithine (de λεχιθος, jaune d'œuf), parce qu'on le rencontre en grande quantité dans le jaune d'œuf,..." (I propose to give the first [substance] the name "Lecithin" (from λεχιθος, egg yolk), because one finds it in large quantities in egg yolk,....)
- Theodore Gobley "Sur la lécithine et la cérébrine"; Journal de Pharmacie et de Chimie 1874,t20, 98-103, 161-166". Missing or empty
- Supplier's website with lecithin applications
- Iwata T, Kimura Y, Tsutsumi K, Furukawa Y, Kimura S (February 1993). "The effect of various phospholipids on plasma lipoproteins and liver lipids in hypercholesterolemic rats". J. Nutr. Sci. Vitaminol. 39 (1): 63–71. doi:10.3177/jnsv.39.63. PMID 8509902.
- Jimenez MA, Scarino ML, Vignolini F, Mengheri E (July 1990). "Evidence that polyunsaturated lecithin induces a reduction in plasma cholesterol level and favorable changes in lipoprotein composition in hypercholesterolemic rats". J. Nutr. 120 (7): 659–67. PMID 2366101.
- Kaayla T. Daniel, PhD, CCN (Winter 2003). "Soy Lecithin: From Sludge to Profit". Wise Traditions in Food, Farming, and the Healing Arts 4 (4).
- J Nutr. 1965 Jan;85:107-12., FATTY LIVERS PRODUCED IN ALBINO RATS BY EXCESS NIACIN IN HIGH FAT DIETS. II. EFFECT OF CHOLINE SUPPLEMENTS.
- British Journal of Nutrition (1996), 75:471-481 Cambridge University Press, Cholesterol-lowering effect of soyabean lecithin in normolipidaemic rats by stimulation of biliary lipid secretion
- Iowa State University Animal Industry Report 2006, Soy Lecithin but Not Egg Lecithin Decreased the Plasma Cholesterol Concentration in Golden Syrian Hamsters
- Life Sciences, Volume 67, Issue 21, 13 October 2000, Pages 2563-2576, Dietary polyenylphosphatidylcholine decreases cholesterolemia in hypercholesterolemic rabbits: Role of the hepato-biliary axis.
- J Pharm Pharmacol. 2005 Jul;57(7):889-96, Phytostanol tablets reduce human LDL-cholesterol.
- Discussion Forum: American Academy of Allergy, Asthama, and Immunology
- Unisci.com, Why Eggs Don't Contribute Much Cholesterol To Diet.
- Gertruida M Marx, Dissertation submitted in fulfillment of requirements for the degree Doctor of Philosophy in the Faculty of Health Sciences, University of the Free State, South Africa. December 2010. MONITORING OF GENETICALLY MODIFIED FOOD PRODUCTS IN SOUTH AFRICA
- Regulation (EC) 50/2000
- John Davison, Yves Bertheau (2007) EU regulations on the traceability and detection of GMOs: difficulties in interpretation, implementation, and compliance CAB Reviews: Perspectives in Agriculture, Veterinary Science, Nutrition, and Natural Resources 2(77)
- (Reb Yehonatan Levy, Shomer Kashrut Mashgiach - based upon halachic rulings of CRC - Chicago Rabbinic Council, and from shiurim/lessons by Rabbi D. Raccah on "Pesach Preparations" following commentary from former Rishon-LeTzion Rav Ovadia Yosef). OK Kosher Certification, Keeping Kosher for Pesach. Retrieved on September 10, 2008.
- Islamic Food and Nutrition Council of America FAQ, IFANCA: Consumer FAQ. Retrieved on July 7, 2010. The practice of consuming Halal products is not widespread among Muslims, the practice is common with Muslims who follow Sharia laws.
- Introduction to Lecithin (University of Erlangen)
- FDA Industry guideline for soy lecithin labeling broken link
- Phosphatidylcholine info
- Use of lecithin for recurrent plugged ducts
- European Lecithin Manufacturers Association official website
- The International Lecithin & Phospholipid Society Website