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Cod liver oil

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This article is about the fish oil. For the traditional Newfoundland song, see Cod Liver Oil (song).
"FCLO" redirects here. For the English football team, see Leyton Orient FC.

Modern cod liver oil capsules
Cod liver oil with malt extract
British Ministry of Food (November 1946)

Cod liver oil is a dietary supplement derived from liver of Atlantic cod (Gadus morhua).[1] As with most fish oils, it contains the omega-3 fatty acids eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA), and also vitamin A and vitamin D.

Historically, it was given to children in the United States in the 19th century as a patent medicine and by the end of the century was being praised by doctors in medical journals.[2][3] After it was shown, in 1920, that vitamin D deficiency was the cause of rickets, cod liver oil was given as a rich source of vitamin D.[4][5][6]

History

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Scott's Emulsion of Pure Cod Liver Oil Trade Card
Children being given cod liver oil, Cambridgeshire, England, 1944

In northern European countries, cod liver oil had a long history of folklore medical uses, including applied to the skin and taken orally as a treatment for rheumatism and gout.[7] In the 1800s, cod liver oil became popular as a bottled medicinal product for oral consumption – a teaspoon a day – with both pale and brown oils being used. The trigger for the surge in oral use was the observation made in several European countries starting with Germany[8] in the 1820s and spreading to other countries into the 1860s that young children fed cod liver oil did not develop rickets.[7] In northern Europe and the United States, the practice of giving children cod liver oil to prevent rickets persisted well in the 1950s. This overlapped with the fortification of cow's milk with vitamin D, which began in the early 1930s.[7]

Knowledge of cod liver oil being rickets-preventive in humans carried over to treating animals. In 1899, London surgeon John Bland-Sutton was asked to investigate why litters of lion cubs at the London Zoo were dying with a presentation that included rickets. He recommended that the diets of the pregnant and nursing females and the weaned cubs be switched from lean horse meat to goat – including calcium- and phosphorus-containing bones – and cod liver oil, solving the problem. Subsequently, researchers realized that animal models such as dogs and rats could be used for rickets research,[9] leading to the identification and naming of the responsible vitamin in 1922.[10]

In 1914, American researchers Elmer McCollum and Marguerite Davis had discovered a substance in cod liver oil which later was named "vitamin A".[11] Edward Mellanby, a British researcher, observed that dogs that were fed cod liver oil did not develop rickets, and (wrongly) concluded that vitamin A could prevent the disease. In 1922, McCollum tested modified cod liver oil in which the vitamin A had been destroyed. The modified oil cured the sick dogs, so McCollum concluded the factor in cod liver oil which cured rickets was distinct from vitamin A. He called it vitamin D because it was the fourth vitamin to be named.[11][12][13]

Once discovered, vitamins were actively promoted in articles and advertisements in McCall's, Good Housekeeping, and other media outlets.[14] Marketers enthusiastically promoted cod-liver oil, a source of vitamin D, as "bottled sunshine", and bananas as a "natural vitality food".[15]

Manufacture

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A cod
Making and loading of cod liver oil, Conche, Newfoundland, 1857

Cod liver oil has traditionally come in many grades. Cod liver oil for human consumption is pale and straw-colored, with a mild flavor. Scandinavian Vikings produced cod liver oil by laying birch tree branches over a kettle of water, and fresh livers were laid over the branches. The water was brought to a boil and as the steam rose, the oil from the liver dripped into the water and was skimmed off. There was also a method for producing fresh raw cod liver oil.[16]

In the Industrial Revolution, cod liver oil became popular for industrial purposes. Livers placed in barrels to rot, with the oil skimmed off over the season, was the main method for producing this oil. The resulting oil was brown and foul-tasting. In the 1800s cod liver oil became popular as a medicine and both pale and brown oils were used. Brown oils were common because they were cheaper to produce. Some doctors believed in only using the fresh pale oil, while others believed the brown oil was better. The rancid brown oils tended to cause intestinal upset.[16]

The Möller Process was invented by Peter Möller in 1850. The livers are ground with water into a slurry, then this is gently simmered until the oil rises to the top. The oil is skimmed off and purified.[17] Other methods used in modern times include the Cold Flotation Process, pressure extraction, and pressure cooking. These all require further purification steps to get a pure oil.[18]

Therapeutic uses

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Though similar in fatty acid composition to other fish oils, cod liver oil has higher concentrations of vitamins A and D. According to the United States Department of Agriculture, a tablespoon (13.6 grams or 14.8 mL) of cod liver oil contains 4,080 μg of vitamin A and 34 μg (1360 IU) of vitamin D.[19] The Dietary Reference Intake of vitamin A is 900 μg per day for adult men and 700 μg per day for women.

Cod liver oil is approximately 20% omega-3 fatty acids. For this reason, cod liver oil may be beneficial in secondary prophylaxis after a heart attack.[20] Diets supplemented with cod liver oil have been demonstrated to have beneficial effects on psoriasis,[21] and daily supplementation has been shown to be correlated with lower rates of high-severity depression.[22]

Potential adverse effects

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Retinol (Vitamin A)

For vitamin A, a tablespoon (13.6 g) of cod liver oil contains 136% of the adult UL, 680% of the UL for children ages 1-3 years, and 453% of the UL for children ages 4-8 years. Even a teaspoon a day (1/3 of a tablespoon) exceeds the UL for children ages 1-8 years.[19] Vitamin A accumulates in the liver, and can reach harmful levels sufficient to cause hypervitaminosis A.[23]

Reducing fatty acid oxidation and environmental toxin exposure requires purification processes as part of manufacturing of refined fish oil products.[24]

Other uses

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In Newfoundland, cod liver oil was sometimes used as the liquid base for traditional red ochre paint, the coating of choice for use on outbuildings and work buildings associated with the cod fishery.

In Tübingen, Germany, drinking a glass of cod liver oil is the punishment for the participants in the last-place boat at the traditional Stocherkahnrennen, an annual punting boat race.[citation needed]

See also

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References

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  1. ^ "STANDARD FOR FISH OILS CODEX STAN 329-2017" (PDF). CODEX ALIMENTARIUS COMMISSION, World Health Organization. 2017. Retrieved 28 January 2022.
  2. ^ Twain, Mark; Smith, Harriet Elinor; Griffin, Benjamin; Fischer, Victor; Frank, Michael B.; Goetz, Sharon K.; Myrick, Leslie Diane (2010). Autobiography of Mark Twain. Berkeley, Calif: University of California Press. ISBN 9780520267190. Cod-liver oil was a common remedy for all diseases, and it was an unspeakably detestable thing to take.
  3. ^ Stone, A. (1884). "On the Practical Uses of Cod-Liver Oil". The Boston Medical and Surgical Journal. 44 (15): 292–295. doi:10.1056/nejm185105140441502. ISSN 0096-6762.
  4. ^ Rajakumar, K. "Vitamin D, Cod-Liver Oil, Sunlight, and Rickets: A Historical Perspective. 2003". Pediatrics. 112 (2): 132–135.
  5. ^ Pileggi VJ, De Luca HF, Steenbock H (September 1955). "The role of vitamin D and intestinal phytase in the prevention of rickets in rats on cereal diets". Archives of Biochemistry and Biophysics. 58 (1): 194–204. doi:10.1016/0003-9861(55)90106-5. PMID 13259690.
  6. ^ Ford JA, Colhoun EM, McIntosh WB, Dunnigan MG (August 1972). "Biochemical response of late rickets and osteomalacia to a chupatty-free diet". British Medical Journal. 3 (5824): 446–447. doi:10.1136/bmj.3.5824.446. PMC 1786011. PMID 5069221.
  7. ^ a b c Hernigou P, Auregan JC, Dubory A (March 2019). "Vitamin D: part II; cod liver oil, ultraviolet radiation, and eradication of rickets". International Orthopaedics. 43 (3): 735–749. doi:10.1007/s00264-019-04288-z. PMID 30627846.
  8. ^ Ihde, Aaron J. (1975). "Studies on the History of Rickets. II : The Roles of Cod Liver Oil and Light". Pharmacy in History. 17 (1): 13–20 – via JSTOR.
  9. ^ Chesney RW, Hedberg G (August 2010). "Metabolic bone disease in lion cubs at the London Zoo in 1889: the original animal model of rickets". J Biomed Sci. 17 Suppl 1 (Suppl 1): S36. doi:10.1186/1423-0127-17-S1-S36. PMC 2994403. PMID 20804612.
  10. ^ Jones G (April 2022). "100 YEARS OF VITAMIN D: Historical aspects of vitamin D". Endocrine Connections. 11 (4). doi:10.1530/EC-21-0594. PMC 9066576. PMID 35245207.
  11. ^ a b Wolf G (June 2004). "The discovery of vitamin D: the contribution of Adolf Windaus". The Journal of Nutrition. 134 (6): 1299–302. doi:10.1093/jn/134.6.1299. PMID 15173387.
  12. ^ Carere S (25 July 2007). "Age-old children's disease back in force". Toronto Star. Archived from the original on 17 May 2008. Retrieved 24 August 2010.
  13. ^ McClean FC, Budy AM (January 1964). "Vitamin A, Vitamin D, Cartilage, Bones, and Teeth". Vitamins and Hormones. Vol. 21. Academic Press. pp. 51–52. Archived from the original on 19 March 2023. Retrieved 19 March 2023.
  14. ^ Wendt D (2015). "Packed full of questions: Who benefits from dietary supplements?". Distillations Magazine. 1 (3): 41–45. Retrieved 22 March 2018.
  15. ^ Price C (Fall 2015). "The healing power of compressed yeast". Distillations Magazine. 1 (3): 17–23. Retrieved 20 March 2018.
  16. ^ a b "Extra-Virgin Cod Liver Oil History". Archived from the original on 11 October 2016. Retrieved 14 October 2016.
  17. ^ "World Class Processing". Archived from the original on 16 October 2016. Retrieved 14 October 2016.
  18. ^ "The Fish Liver Oil Industry" (PDF). Archived (PDF) from the original on 18 October 2016. Retrieved 14 October 2016.
  19. ^ a b "Fish oil, cod liver". U.S. Department of Agriculture. Retrieved 11 April 2025.
  20. ^ von Schacky, C (2000). "n-3 Fatty acids and the prevention of coronary atherosclerosis". Am J Clin Nutr. 71 (1 Suppl): 224S – 7S. doi:10.1093/ajcn/71.1.224s. PMID 10617975.
  21. ^ Wolters, M. (2005). "Diet and psoriasis: experimental data and clinical evidence". British Journal of Dermatology. 153 (4): 706–14. doi:10.1111/j.1365-2133.2005.06781.x. PMID 16181450. S2CID 1426074.
  22. ^ Raeder MB, Steen VM, Vollset SE, Bjelland I (August 2007). "Associations between cod liver oil use and symptoms of depression: the Hordaland Health Study". J Affect Disord. 101 (1–3): 245–9. doi:10.1016/j.jad.2006.11.006. PMID 17184843.
  23. ^ Paul Lips (May 2003). "Hypervitaminosis A and fractures". N Engl J Med. 348 (4): 1927–28. doi:10.1056/NEJMe020167. PMID 12540650.
  24. ^ Bays H E (March 2007). "Safety Considerations with Omega-3 Fatty Acid Therapy". The American Journal of Cardiology. 99 (6 (Supplement 1)): S35–43. doi:10.1016/j.amjcard.2006.11.020. PMID 17368277.
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