The Medicinal Value of Cod Liver Oil

Cod Liver Oil has been used as a medicine for centuries although its clinical use did not begin until the mid 17th century when it was given to people suffering with bone disease and rheumatism. At that time no-one knew why it worked.

By 1824, Chevreul had demonstrated that fats were esters of glycerol and fatty acids of differing chain length. At the time, it was thought that fats could be synthesized only by the plant kingdom. However, by 1850, it had been found from balance studies that animals also could synthesize fats from carbohydrates. The caloric value of fat was determined in the 1860s and shown to be more than double that of carbohydrate. In 1907, it was shown that this was also true when fat was used as a source of energy for physical work. The special value of cod liver oil for the prevention and treatment of rickets was well known by 1850 but was not to be explained until much later.

By the 1840s there were many accounts of the medicinal value of one particular lipid material, cod liver oil. For example: "Whether the disease of rickets be in its most severe form, with swollen joints and crooked legs, or at its commencement, the cod liver oil will supersede every other means of cure" and "A case of inflammation of the eyelids and intolerance of light was cured within ten days with cod liver oil as were several cases of conjunctivitis of the cornea". De Jongh (1849) speculated about the mode of action of various cod liver oils in relation to their fatty acid make-up.

Vitamin A supplementation is an important public health intervention to reduce mortality from infections among children in developing countries. In the 1980s and early 1990s, several large randomized, double-blind, placebo-controlled clinical trials were conducted in developing countries around the world, and these studies showed that vitamin A supplementation could reduce child mortality by about one-third (Beaton et al. 1993). Improving the vitamin A status of children through vitamin A supplementation is one of the most cost-effective health interventions known (World Bank 1993). High-dose vitamin A is now recommended therapy for measles in many developing countries and for selected circumstances in developed countries. Although vitamin A has been undergoing investigation in clinical trials in the last two decades, these recent trials are largely a continuation of clinical investigation that began in the 1920s.

In the last fifteen years, a large series of controlled clinical trials showed that vitamin A supplementation reduces morbidity and mortality of children in developing countries. It is less well known that vitamin A underwent two decades of intense clinical investigation prior to World War II. In the 1920s, a theory emerged that vitamin A could be used in "anti-infective" therapy. This idea, largely championed by Edward Mellanby, led to a series of at least 30 trials to determine whether vitamin A�usually supplied in the form of cod-liver oil�could reduce the morbidity and mortality of respiratory disease, measles, puerperal sepsis, and other infections. The early studies generally lacked such innovations known to the modern controlled clinical trial such as randomization, masking, sample size and power calculations, and placebo controls. Results of the early trials were mixed, but the pharmaceutical industry emphasized the positive results in their advertising to the public. With the advent of the sulfa antibiotics for treatment of infections, scientific interest in vitamin A as "anti-infective" therapy waned. Recent controlled clinical trials of vitamin A from the last 15 years follow a tradition of investigation that began largely in the 1920s.

Vitamin A is a vitamin, a substance found in foods that is necessary for human health. Vitamin A is found in liver, various dairy products with fat, such as milk, cheese, butter and ice cream, and in fatty fish such as herring, sardines, and tuna. It can also be found in the liver oils of shark, cod, and halibut. Vitamin A is known to play a part in cell differentiation, a process by which cells "mature." Differentiation helps prevent inappropriate growth, such as the uncontrolled cell growth that is seen in cancer. Many studies in animals show that vitamin A and similar compounds decrease the incidence of cancer.

Anti-atherogenic diet supplemented with "Eicolen" (30% linseed oil, and 70% cod-liver oil, 9 grams per day) has been analyzed in 10 cases of ischemic heart disease, and in 11 cases of ischemic heart disease complicated by impaired glucose tolerance. The fish and vegetable PUFA omega-3 from "Eicolen" have been found to improve clinical condition as well as to modify erythrocyte membrane fatty acid composition.

There is growing evidence that dietary n-3 polyunsaturated fatty acids (n-3 PUFAs), abundant in marine organisms, may reduce the development of cardiovascular disease.

  • Kenneth J. Carpenter. Early Ideas on the Nutritional Significance of Lipids. The Journal of Nutrition Vol. 128 No. 2 February 1998, pp. 423S-426S
  • Beaton, G. H., Martorell, R., L'Abbe, K. A., Edmonston, B., McCabe, G., Ross, A. C. & Harvey, B. (1993) Effectiveness of Vitamin A Supplementation in the Control of Young Child Morbidity and Mortality in Developing Countries. ACC/SCN State-of-the-Art Nutrition Policy Discussion Paper No. 13, United Nations.
  • Richard D. Semba. Vitamin A as "Anti-Infective" Therapy, 1920-1940. Journal of Nutrition. 1999;129:783-791.
  • Kulakova SN, Gapparova KM, Pogozheva AV, Levachev MM. Evaluation of the effects of fish and vegetable omega-3 PUFA complex on the erythrocyte fatty acid composition in patients with ischemic heart disease and impaired glucose tolerance. Vopr Pitan 1999;68 (5-6):26-9