COD-LIVER OIL

pale yellow oil obtained from the liver of the cod and related fish, particularly the Atlantic cod, Gadus morhua, and other species of the family Gadidae. Cod-liver oil is a source of vitamins A and D. It is used in medicine to correct abnormal calcium and phosphorous metabolism resulting from a lack of vitamin D as in rickets, infantile tetany, and osteomalacia. It is also used in feeds for poultry and other animals. In the 19th century cod-liver oil was a folk remedy for several wasting diseases. By 1922 its medicinal value was established and related to the presence of vitamins A and D. Vitamin potency varies with the age and species of fish; the older and the less fatty the liver, the more potent are the vitamins. The chief countries producing cod-liver oil are Norway, Japan, Iceland, and Poland. Fresh cod livers are digested by steam, water, acid, or alkali to produce the oil. Medicinal grades are chilled, and congealed stearic acid and other fatty acids are filtered off. Chemically, cod-liver oil is a typical marine-animal oil. It is high in polyunsaturated fatty acids, a valuable aspect in nutrition but one that makes it subject to oxidation, rancidification, and destruction of vitamin A when it is exposed to air. Cod-liver oil is a mixture of glycerides of many fatty acids, predominantly oleic acid, gadoleic acid, and palmitoleic acid. See also fish oil.