Nutrition in the News
18 January 2002
CHOLINE
At the end of August 2001, the Food and Drug Administration published notification that food and dietary supplement manufacturers could add nutrient content claims to their labels concerning choline. So what is this "choline"?
Choline is not recognized at this time as a vitamin or as an essential nutrient for most people. The reason is that little evidence exists to show that choline-deficient diets are harmful to human health. An essential nutrient is one that cannot be synthesized in adequate amounts within the body and must come from an external source such as food. Only one study has been published using healthy people with otherwise normal and adequate diets, deficient only in choline. The men were unable to synthesize enough choline on their own and, as a consequence, developed a health problem--liver dysfunction. No similar studies have been completed for women, children, infants, or older adults. Nor has this one study been replicated by others. All the other research on choline has been done in laboratory animals, in vitro, or on very ill individuals with serious metabolic problems. Thus, the Food and Nutrition Board of the National Research Council concludes that, at present, there is inadequate information to establish an RDA for choline.
Choline is clearly critical to life. Choline is a structural component of cell membranes. Choline functions in nerve transmission, transmembrane signaling, and lipid and cholesterol transport. Choline can be synthesized within cells by transference of a methyl group from S-adenosylmethionine to a phospolipid. Methyl-group transfers such as this involve folate (as we discussed in the November 2001 in-serving meeting). Need for dietary choline, therefore, is closely linked to dietary intake of the amino acid methionine, folate, and vitamin B12.
Lecithin is a popular name for phosphatidylcholine, the structural and main functional form of choline in the body.
Because very few foods have been analyzed for choline content, it is all but impossible to determine how much choline people are consuming. And, so far, it has not been possible to carry out epidemiological studies comparing populations with high or low choline intake. The Food and Nutrition Board has set 550 milligrams per day for adult men and 425 milligrams per day for adult women as the probable Adequate Intake (not the same as a Recommended Intake).
Choline is widely distributed in foods. Foods that are known to be especially rich in choline or choline-containing compounds include milk, liver, eggs, and peanuts. Lecithin added to processed foods can increase choline intake significantly.
Animal studies have linked dietary choline with improved memory, reduced cardiovascular disease, and reduced risk of liver cancer. Some human studies have used choline-containing compounds to treat dementia but did not examine whether normal memory was improved nor whether dementia could be prevented. Three human studies showed that choline supplementation is associated with a modest lowering of serum cholesterol. In addition, choline supplements could lower plasma homocysteine concentration. Thus, in two ways choline supplementation or adequate dietary choline has the potential to reduce CVD risk. As for choline and cancer, there are NO human data at present.
Extremely high doses of choline have adverse effects in humans. Given to treat brain disorders, choline has caused fishy body odor, sweating, vomiting, and mild liver toxicity. The doses at which these effects occurred were 8-20 grams per day for two weeks or more. Although very little safety data is available, the Food and Nutrition Board has set 3.5 grams per day as the Tolerable Upper Intake Level for adults, below which no toxic side effects would be expected. Lower levels are set for children and pregnant and nursing women.
Reference: Dietary Reference Intakes for Thiamin, Riboflavin, Niacin, Vitamin B-6, Folate, Vitamin B-12, Pantothenic Acid, Biotin, and Choline. Institute of Medicine, National Academy Press, Washington, DC. 1998.
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