choline

The N,N,N-trimethylethanolammonium cation, with an undefined counteranion, X⁻

Choline is a water-soluble essential nutrient. ^{[1] [2][3][4]} It is usually grouped within the Vitamin B complex. Choline generally refers to the various quaternary ammonium salts containing the N,N,N-trimethylethanolammonium cation.

These naturally-occuring ammonium salts are found in the lipids that make up cell membranes and in the neurotransmitter acetylcholine. Adequate intakes (AI) for this micronutrient of between 425 to 550 milligrams daily, for adults, have been established by the Food and Nutrition Board of the Institute of Medicine of the National Academy of Sciences.

History

Choline was discovered by Andreas Strecker in 1864 and chemically synthesized in 1866. In 1998 choline was classified as an essential nutrient by the Food and Nutrition Board of the Institute of Medicine (U.S.A.).

Chemistry

Choline is a quaternary saturated amine with the chemical formula (CH₃)₃N⁺CH₂CH₂OHX⁻, where X⁻ is a counterion such as chloride (see choline chloride), hydroxide or tartrate. Choline chloride, in mixture with urea is used as a solvent ( DES ) and the salicylate salt is used topically for pain relief of aphthous ulcers.

Physiology

Choline metabolism. (Choline is green box at left, second from the bottom.)

Choline and its metabolites are needed for three main physiological purposes: structural integrity and signaling roles for cell membranes, cholinergic neurotransmission (acetylcholine synthesis), and as a major source for methyl groups via its metabolite, trimethylglycine (betaine) that participates in the S-adenosylmethionine synthesis pathways.

When choline is metabolized by the body, it may form trimethylamine, a compound with a fishy odor. Hence, when large amounts of choline are taken the person may suffer from a fishy body odor.

Choline and Anxiety

Despite its importance in the central nervous system as a precursor for acetylcholine and membrane phosphatidylcholine, the role of choline in mental illness has been little studied. In a large population-based study, choline concentrations were negatively associated with anxiety symptoms in subjects aged 46–49 and 70–74 years who had valid information on plasma choline concentrations and symptoms of anxiety. ^[5]

Choline as a supplement

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It is well established that supplements of methyl group transfer vitamins B6, B12, folic acid reduce the blood titer of homocysteine and so may prevent heart disease.^[6] Choline is a necessary source of methyl groups for methyl group transfer. Supplements of lecithin/choline were found to reduce heart disease in laboratory studies.^{[citation needed]} The reduction in heart disease with lecithin supplements may however relate more to the cholesterol carrying capacity of lecithin than to the methyl group transfer role of choline.^[specify]

Choline supplements are often taken as a form of 'smart drug' or nootropic, due to the role that the neurotransmitter acetylcholine plays in various cognition systems within the brain. Choline is a chemical precursor or "building block" needed to produce the neurotransmitter acetylcholine, and research suggests that memory, intelligence and mood are mediated at least in part by acetylcholine metabolism in the brain.^{[citation needed]} In study on rats, a correlation was shown between choline intake during pregnancy and mental task performance of the offspring^[7]; however, the same correlation has not been shown in humans^[8]. However, this human study admits "Women in the current study consumed their usual diets. They were not eating choline-enriched diets and were not receiving choline supplementation. Therefore, our results indicate that choline concentrations in a physiologic range observed among women consuming a regular diet during pregnancy are not related to IQ in their offspring. We cannot rule out the possibility that choline supplementation could have an IQ effect."

The compound's quaternary amine renders it lipid insoluble which might suggest it would be unable to cross the blood-brain barrier. However, despite choline's lipid insolubility, a choline transporter exists that allows transport across the blood-brain barrier. The efficacy of these supplements in enhancing cognitive abilities is a topic of continuing debate.

Some people who practice lucid dreaming use galantamine with choline bitartrate or alpha-GPC in the belief it may increase their odds of having a lucid dream. Acetylcholine precursors such as choline and galantamine may help improve memory and fight the symptoms of Alzheimer's disease.^{[citation needed]}

The Food and Drug Administration (FDA) requires that infant formula not made from cow's milk be supplemented with choline.^[9]

Due to its role in lipid metabolism, choline has also found its way into nutritional supplements which claim to reduce body fat; but there is little or no evidence to prove that it has any effect on reducing excess body fat or that taking high amounts of choline will increase the rate at which fat is metabolised.

Choline and soy lecithin is also believed^[who?] to aid in the relief of plugged milk ducts in nursing mothers.^{[citation needed]}

Fish odor syndrome

Choline is a precursor to trimethylamine, which some persons are not able to break down due to a genetic disorder. Persons suffering from this disorder, called trimethylaminuria, may suffer from a strong fishy or otherwise unpleasant body odor due to the body's release of odorous trimethylamine. A body odor will occur even on a normal diet - i.e., one that is not particularly high in choline. Persons with trimethylaminuria are advised to restrict the intake of foods high in choline; this may help to reduce the sufferer's body odor.

Choline hydroxide

Choline hydroxide is one of the class of phase transfer catalysts which are used to carry the hydroxide ion into organic systems, and because of this it is considered a strong base. It is the least costly phase transfer catalyst, and is used as a cheap method of stripping photoresists in circuit boards. Choline hydroxide is not completely stable and it slowly breaks down into trimethylamine.

Sources

The foods richest in phosphatidylcholine — the major delivery form of choline — are egg yolks, soy, wheat germ and cooked beef, chicken, veal and turkey livers. In 2004, the USDA released its first database of the choline content in common foods.^[10]

The most often available choline dietary supplement is lecithin, derived from soy or egg yolks, often used as a food additive. Phosphatidylcholine is also available as a supplement, in pill or powder form. Supplementary choline is also available as choline chloride, which comes as a liquid due to its hydrophilic properties. Choline chloride is sometimes preferred as a supplement because phosphatidylcholine can have gastrointestinal side effects.

The human body can make some choline, but it is generally recognized that it is important to get dietary choline as well. Although most foods have at least a little choline, some people may have to pay close attention to get enough in their diets, particularly if they do not eat many whole eggs.^[11]

Additional images

Choline (C5H14NO+)

Choline chloride

Choline hydroxide

See also

• Cytidine diphosphate choline

References

1. ^ Jane Higdon, "Choline", Micronutrient Information Center, Linus Pauling Institute
2. ^ "Choline, PDRHealth
3. ^ "Choline" (An interview with Steven Zeisel, Editor-in-Chief of the Journal of Nutritional Biochemistry), Radio National Health Report with Norman Swan, Monday 17 April 2000
4. ^ "[1]" Dietary Reference Intakes for Thiamin, Riboflavin, Niacin, Vitamin B6, Folate, Vitamin B12, Pantothenic Acid, Biotin, and Choline (1998), Institute of Medicine.
5. ^ Bjelland I, Tell GS, Vollset SE, Konstantinova S, Ueland PM, "Choline in anxiety and depression: the Hordaland Health Study.", The American Journal of Clinical Nutrition.
6. ^ Verhoef, Petra; Stampfer, Meir J; Buring, Julie F; Gaziano, J. Michael; Allen, Robert H; Stabler, Sally P; Reynolds, Robert D; Kok, Frans J; Hennekens, Charles H; Willett, Walter C (1996). "Homocysteine Metabolism and Risk of Myocardial Infarction: Relation with Vitamins B6, B12, and Folate". American Journal of Epidemiology 143 (9): 845–859. 
7. ^ Robert J. Sternberg, "Handbook of intelligence", Cambridge University Press, 2000, ISBN 0521596483, 9780521596480, page 77.
8. ^ Caroline Signore, Per Magne Ueland, James Troendle and James L Mills, "Choline concentrations in human maternal and cord blood and intelligence at 5 y of age", American Journal of Clinical Nutrition, Vol. 87, No. 4, 896-902, April 2008 (abstract).
9. ^ Isadora B. Stehlin, Infant Formula: Second Best but Good Enough, U.S. Food and Drug Administration.
10. ^ "USDA Database for the Choline Content of Common Foods - 2004", USDA Nutrient Data Laboratory
11. ^ Hasler C.M. The Changing Face of Functional Foods. J. Am. Coll. Nutr. 19, 2000; 499S-506