cod liver oil Routine administration of a spoonful of cod liver oil, on a daily basis, to young children, by caring parents, was very common in the 1940s and 50s. Most children were revulsed by the practice because of the unpalatability of the fishy tasting oil, and doubtless extracted a variety of rewards for compliance. As the name implies, cod liver oil is from the liver of the cod (Gadus callarias), simply freed from solid fat by filtration at low temperature.

The oil is a rich source of vitamins A and D and also contains essential unsaturated fatty acids. Vitamin A is important for photoreceptor mechanisms in the retina and the integrity of epithelia, so deficiency can lead to night blindness. Vitamin D is essential for the absorption of calcium and phosphorus by the body, a prerequisite for bone formation. Vitamin D is also formed in the skin by the action of sunlight (UV radiation). Children growing up in poor urban areas, with few places to play outside, were commonly the victims of Vitamin D deficiency in the early part of the twentieth century, when rickets was common. Inadequate bone formation leads to bending in weight-bearing bones, giving rise to bow legs and knock knees. Paradoxically, rickets is not uncommon in the tropics because of the swaddling of infants. Vitamin D deficiency in adults leads to osteomalacia. There were attempts to make cod liver oil more palatable by forming oil-in-water emulsions with flavoured water, or mixing the oil with malt. It was later discovered that halibut liver oil (from Hippoglossus hipoglossus) contains far higher concentrations of both Vitamins A and D so that a daily dose could be accommodated in a small gelatin capsule that was easily swallowed and tasteless.

Alan W. Cuthbert

cod liver oil The oil from codfish liver; the classic source of vitamins A and D, used for its medicinal properties long before the vitamins were discovered; also a rich source of omega‐3 polyunsaturated fatty acids. An average sample contains 120–1200 μg vitamin A and 1–10 μg vitamin D per gram. British Pharmacopoeia standard: minimum 180 μg vitamin A and 2 μg vitamin D per gram.

cod liv·er oil • n. oil pressed from the fresh liver of cod, which is rich in vitamins D and A.

cod liver oil (kod) n. a pale yellow oil, extracted from the livers of cod and related fish, that is rich in vitamins A and D and used in the treatment and prevention of deficiencies of these vitamins (e.g. rickets).