Cod liver oil

This article is about the fish extract, for the traditional Newfoundland song, see "Cod Liver Oil (song)".

Cod liver oil is a nutritional supplement that is derived from cod livers. It has high levels of the omega-3 fatty acids, EPA and DHA, and very high levels of vitamin A, and vitamin D. It is widely taken to ease the symptoms of arthritis. It was commonly given to children.

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Characteristics

Depending on the quality of the oil, the flavor and aroma range from a mild sardine-like flavor, to an intense and obnoxious odor of rotten fish and rancid oil. High quality cod liver oil is a pale-yellow, thin, oily liquid, having a peculiar, slightly fishy, but not rancid odor, and a bland, slightly fishy taste. Manufacturers sometimes add flavorings, such as citrus or mint essence, to cod liver oil to make it more palatable.

Manufacture

Cod liver oil is made by cooking cod livers with steam, and then pressing/decanting the cooked livers to extract the oil. This is in contrast to fish oils, which are extracted from the cooked whole body tissues of fatty fish during the manufacture of fish meal.

Therapeutic uses

Cod liver oil is widely taken to ease the pain and joint stiffness associated with arthritis,^[1] but has also been clinically proven to have a positive effect on heart,^[2][3] bone,^[4] and brain,^[5] as well as helping to nourish skin,^[6] hair, and nails.

Cod liver oil and fish oil are similar, but cod liver oil has much higher levels of vitamins A and D. Many adults don't meet the RDA for Vitamin D.^{[7][8][9][10]}

In 2005, a study by researchers at the University of California found that Vitamin D may lower the risk of developing different types of cancers, halving the chances of getting breast, ovarian, and colon cancers.^[11]

Use of cod liver oil during pregnancy is associated with lower risk of Type I diabetes in the offspring.^[12] This effect was found only in mothers taking cod liver oil, not in mothers taking multivitamin supplements. Cod liver oil taken by nursing mothers improves the breast milk by increasing the amount of fatty acids, which promotes brain development, and the amount of vitamin A, which helps prevent infections, but the level of vitamin D is unchanged.

Adverse effects

Because cod liver oil has a very high level of Vitamin A, it is possible to exceed the Recommended Dietary Allowance (RDA) of vitamin A. Vitamin A accumulates in body fat, and can reach harmful levels sufficient to cause hypervitaminosis A.

It is impossible to obtain therapeutic amounts of the fatty acids EPA and DHA from cod liver oil without exceeding the RDA for vitamin A.^{[citation needed]}

A high intake of cod liver oil by pregnant women is associated with a nearly five-fold increased risk of gestational hypertension,^[13] although this study did not control for mercury, which can be present in harmful amounts in fish and which is another cause of hypertension.^[14]

Some urge caution when taking cod liver oil and other fish-based supplements since they may contain elevated levels of toxins such as mercury and PCBs increasingly found in fish. Some supplement companies regularly test cod liver oil for purity, while others do not.

Other uses

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.

See also

• Vitamin A overdose
• Shark liver oil

References

1. ^ Gruenwald J, Graubaum HJ, Harde A. Effect of cod liver oil on symptoms of rheumatoid arthritis. 2002. Adv Ther 19:101-107. PMID 12069368
2. ^ Knapp, HR, et al (1987). "The Effect of Cod liver oil on the Development of Atherosclerosis in an Animal Model.". Proceedings of the AOCS: pp. 35-40.
3. ^ von Schacky, C. (2000). "n-3 Fatty acids and the prevention of coronary atherosclerosis". Am J Clin Nutr 71 ((1 Suppl)): 224S-7S.
4. ^ Akpede, GO, et al (1999). "Rickets and deprivation: a Nigerian study.". J R.Soc.Health 119: 216-22.
5. ^ Cod liver oil, fish oil and Omega 3, "Cod liver oil and depression".
6. ^ Terkelsen, LH, et al (2000). "Topical application of cod liver oil ointment accelerates wound healing: an experimental study in wounds in the ears of hairless mice.". J Plast. Reconstr. Surg. 34: 15-20.
7. ^ Reginster JY. The high prevalence of inadequate serum vitamin D levels and implications for bone health. 2005. Curr Med Res Opin 21:579-586. DOI: 10.1185/030079905X41435 PMID 15899107
8. ^ Calvo MS, Whiting SJ, Barton CN. Vitamin D fortification in the United States and Canada: current status and data needs. 2004. Am J Clin Nutr 80:1710S-1716S. PMID 15585792 full text (free)
9. ^ Peterlik M, Cross HS. Vitamin D and calcium deficits predispose for multiple chronic diseases. 2005. Eur J Clin Invest 35:290-304. DOI: 10.1111/j.1365-2362.2005.01487.x PMID 15860041
10. ^ Cantorna MT, Mahon BD. Mounting evidence for vitamin D as an environmental factor affecting autoimmune disease prevalence. 2004. Exp Biol Med (Maywood) 229:1136-1142. PMID 15564440 full text (free)
11. ^ Garland CF, Garland FC, Gorham ED, et al. The role of vitamin D in cancer prevention. 2006. Am J Public Health 96:252-261. DOI: 10.2105/AJPH.2004.045260 PMID 16380576
12. ^ Stene LC, Ulriksen J, Magnus P, et al. Use of cod liver oil during pregnancy associated with lower risk of Type I diabetes in the offspring. 2000. Diabetologia 43:1093-1098. DOI: 10.1007/s001250051499 PMID 11043854 full-text (free)
13. ^ Olafsdottir AS, Skuladottir GV, Thorsdottir I, et al. Relationship between high consumption of marine fatty acids in early pregnancy and hypertensive disorders in pregnancy. 2006. BJOG 113:301-309. DOI: 10.1111/j.1471-0528.2006.00826.x PMID 16487202
14. ^ Horowitz Y, Greenberg D, Ling G, Lifshitz M. Acrodynia: a case report of two siblings. Arch Dis Child 2002; 86: 453. PMID 12023189