Cod-liver oil as both source and antagonist of vitamin E

Knowledge that cod-liver oil can be toxic when given in excess to various animals dates back to observations by Agduhr (1926).Since about the same time the oil has been known to be deficient in vitamin E, at least as judged by its ability to promote reproduction in rats.Thus although Nelson, Ohrbeck, Jones & Taylor (1928) concluded that the oil contained enough vitamin E to allow reproduction, most other workers (Mattill, 1922;Evans & Bishop, 1923;Hogan & Harshaw, 1926;Sure, 1927) found that it failed to prevent sterility.Hartwell (1927), who observed delayed parturition and fatal uterine haemorrhage in rats receiving large amounts of cod-liver oil, ascribed these abnormalities to lack of vitamin E in the oil.Later investigations proved that cod-liver oil is not merely ineffective as a source of vitamin E, but that it actually intensifies the severity of certain lesions associated with avitaminosis E.Even before the role of vitamin E in preventing nutritional muscular dystrophy was fully recognized the ability of cod-liver oil to precipitate this lesion, particularly in herbivores, was well established (Madsen, McCay & Maynard, 1932-3, 1935).Later Morris (1939) and Shimotori, Emerson & Evans (1939, 1940) showed, in rabbits and guinea-pigs respectively, that a-tocopherol could neutralize the tendency of cod-liver oil to cause muscular dystrophy.According to Mackenzie, Mackenzie & McCollum (1941), however, the ability of a-tocopherol to prevent muscular dystrophy in rabbits was lost when it was administered within a short time of a dose of cod-liver oil, or when cod-liver oil was included in the diet.Presumably these workers were observing the same antagonism between vitamin E and cod-liver oil as was reported by Morris (1939), but this time with the oil in ascendancy.Mattill (1938) suggested that the role of vitamin E in preventing muscular dystrophy was related to its power of checking autoxidation in animal fats (Cummings & Mattill, 1930-1).Dam ( 1 9 4 4 ~) noticed that the body fat of rats became brown when cod-liver oil was included as 20% of their diet.This brown colour, which could be prevented by a-tocopherol, was shown to be associated with the formation of peroxides (Dam & Granados, 1945).Further evidence of the production of muscular dystrophy by codliver oil, in calves under conditions pertaining in practical animal husbandry, was reported by Blaxter, Wood & MacDonald (1953).According to Bruce (1950) the inclusion of only 2% cod-liver oil, in a diet containing 85 yo of whole grain cereals, caused failure of lactation in mice.The defect could be prevented by dosing with a-tocopherol.