Source: Wikipedia & WebMD
Cod liver oil is a nutritional supplement derived from liver of cod fish. As with most fish oils, cod liver oil has high levels of the omega-3 fatty acids, EPA and DHA. Cod liver oil also contains vitamin A and vitamin D. It has historically been taken because of its vitamin A and vitamin D content. It was once commonly given to children, because vitamin D has been shown to prevent rickets and other symptoms of vitamin D deficiency.
Cod liver oil is a nutritional supplement derived from liver of cod fish. As with most fish oils, cod liver oil has high levels of the omega-3 fatty acids, EPA and DHA. Cod liver oil also contains vitamin A and vitamin D. It has historically been taken because of its vitamin A and vitamin D content. It was once commonly given to children, because vitamin D has been shown to prevent rickets and other symptoms of vitamin D deficiency.
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Therapeutic uses
Cod liver oil is widely taken to ease the pain and joint stiffness associated with arthritis.[3] It may have a positive effect on heart,[4][5] bone,[6] as well as helping to repair wounded skin,[7] hair, nails, and teeth.
Cod liver oil and fish oil are similar, but cod liver oil has higher levels of vitamins A and D. According to the USDA, a tablespoon of cod liver oil (13.6 g) contains 4080 μg of retinol (vitamin A) and 34 μg of vitamin D.[1] The Recommended Dietary Allowance of vitamin A is 900 μg per day for adult men and 700 for women, while that for vitamin D is 15 μg per day. The “Tolerable upper intake levels” are 3000 μg/day and 100 μg/day respectively, so people consuming cod liver oil as a source of omega-3 fatty acids should pay attention to how much vitamin A and vitamin D this adds to their diet.[8][9]
Cod liver oil may be an effective complementary measure for long-term treatment of multiple sclerosis.[10]
Use of cod liver oil during pregnancy is associated with lower risk of Type I diabetes in the offspring.[11] (although see adverse effects below). 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.
A Norwegian study of more than 68,000 women reported that female cancer patients who took daily cod-liver oil supplements had significantly reduced mortality (25% for all cancers, 45% for lung cancer) compared to women who did not take such supplements.[12][13]
Adverse effects
Per tablespoon (13.6g), cod liver oil contains 136% of the established daily Tolerable Upper Intake Level (UL) for Preformed Vitamin A (Retinol).[14][15] Vitamin A accumulates in body fat, and can reach harmful levels sufficient to cause hypervitaminosis A.[8] Pregnant women may want to consider consulting a doctor when taking cod liver oil because of the high amount of natural forms of vitamin A such as retinol. High doses of synthetic vitamin A (retinoids) have been shown to cause birth defects.[16] A toxic dose of retinol (vitamin A) is around 25 000 IU/kg (see Retinol#Retinoid overdose (toxicity)), or the equivalent of about 1.25 kg of cod liver oil for a 50-kg person.
The risks of hypervitaminosis and of exposure to environmental toxins such as mercury, polychlorinated biphenyls (PCBs), dioxins, and other contaminants, are reduced when purification processes are applied to produce refined fish-oil products, which consequently contain raised levels of omega-3 fatty acids, such as EPA and DHA.[17]
A high intake of cod liver oil by pregnant women is associated with a nearly fivefold increased risk of gestational hypertension,[18] although this study did not control for mercury, which can be present in harmful amounts in fish[17] and which is another cause of hypertension.[19]
Some urge caution when taking cod liver oil and other fish-based supplements since they may contain elevated levels of toxins such asmercury and PCBs found in fish.[17]
References
1. Rajakumar, K. Vitamin D, Cod-Liver Oil, Sunlight, and Rickets: A Historical Perspective. 2003. Pediatrics 112(2):132-1352.
2. Gruenwald J, Graubaum HJ, Harde A (2002). “Effect of cod liver oil on symptoms of rheumatoid arthritis”. Adv Ther 19 (2): 101–7.PMID 12069368.
3. 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.
4.von Schacky, C. (2000). “n-3 Fatty acids and the prevention of coronary atherosclerosis”. Am J Clin Nutr 71 ((1 Suppl)): 224S–7S.PMID 10617975.
5.Akpede, GO, et al.; Omotara, B.A.; Ambe, J.P. (1999). “Rickets and deprivation: a Nigerian study.”. J R.Soc.Health 119 (4): 216–22.doi:10.1177/146642409911900403.
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 (1): 15–20. doi:10.1080/02844310050160123.
7. a b Paul Lips (8 May 2003). “Hypervitaminosis A and fractures”. N Engl J Med 348 (4): 1927–1928. doi:10.1056/NEJMe020167.PMID 12540650. http://content.nejm.org/cgi/content/short/348/4/347. Retrieved 6 March 2008.
8.Haddad J.G. (30 April 1992). “Vitamin D — Solar Rays, the Milky Way, or Both?”. The New England Journal of Medicine.http://www.nejm.org/search q=vitamin+d&asug=Vitamin#qs=%3Fq%3D%2522too%2Bmuch%2Bvitamin%2Bd%2522%26date%3Dpast20Years. Retrieved 29 January 2012.
10. ^ Swank, Roy L., and Barbara Brewer Duggan. The Multiple Sclerosis Diet Book: A Low-Fat Diet for The Treatment of MS. Doubleday, 1987.
11. ^ Stene LC, Ulriksen J, Magnus P, Joner G (September 2000). “Use of cod liver oil during pregnancy associated with lower risk of Type I diabetes in the offspring”. Diabetologia 43 (9): 1093–8. doi:10.1007/s001250051499. PMID 11043854.
12. ^ Lund, Eiliv; Vanessa Dumeaux, Tonje Braaten, Anette Hjartåker, Dagrun Engeset, Guri Skeie, Merethe Kumle (6 June 2007). “Cohort Profile: The Norwegian Women and Cancer Study—NOWAC—Kvinner og kreft”. International Journal of Epidemiology (Oxford University Press) 2008 (37(1)): 36–41. doi:10.1093/ije/dym137. PMID 17644530. http://ije.oxfordjournals.org/cgi/content/full/37/1/36. Retrieved 12 October 2007.
13. ^ Skeie, G; Braaten T, Hjarta A, Brustad M, Lund E.. “Cod liver oil, other dietary supplements and survival among cancer patients with solid tumors.”. Int J Cancer 125: 1155–60. doi:10.1002/ijc.24422. PMID 19444919.
14. ^ National Nutrient Database for Standard Reference “USDA Nutrition Facts: Fish oil, cod liver” USDA
15. ^ Jane Higdon, Ph.D. of the Linus Pauling Institute “Linus Pauling Institute Micronutirent Center” Oregon State University
16. ^ Myhre AM, Carlsen MH, Bøhn SK, Wold HL, Laake P, Blomhoff R (December 2003). “Water-miscible, emulsified, and solid forms of retinol supplements are more toxic than oil-based preparations”. Am. J. Clin. Nutr. 78 (6): 1152–9. PMID 14668278.http://www.ajcn.org/cgi/pmidlookup?view=long&pmid=14668278.
17. ^ a b c Bays H E (19 March 2007). “Safety Considerations with Omega-3 Fatty Acid Therapy”. The American Journal of Cardiology. 99(Supplement 1) (6): S35–S43. doi:10.1016/j.amjcard.2006.11.020. PMID 17368277.
18. ^ Olafsdottir AS, Skuladottir GV, Thorsdottir I, Hauksson A, Thorgeirsdottir H, Steingrimsdottir L (March 2006). “Relationship between high consumption of marine fatty acids in early pregnancy and hypertensive disorders in pregnancy”. BJOG 113 (3): 301–9. doi:10.1111/j.1471-0528.2006.00826.x. PMID 16487202.
19. ^ Horowitz Y, Greenberg D, Ling G, Lifshitz (2002). “Acrodynia: a case report of two siblings”. Arch Dis Child 86 (6): 453.doi:10.1136/adc.86.6.453. PMC 1762992. PMID 12023189. //www.ncbi.nlm.nih.gov/pmc/articles/PMC1762992/.
Cod liver oil is widely taken to ease the pain and joint stiffness associated with arthritis.[3] It may have a positive effect on heart,[4][5] bone,[6] as well as helping to repair wounded skin,[7] hair, nails, and teeth.
Cod liver oil and fish oil are similar, but cod liver oil has higher levels of vitamins A and D. According to the USDA, a tablespoon of cod liver oil (13.6 g) contains 4080 μg of retinol (vitamin A) and 34 μg of vitamin D.[1] The Recommended Dietary Allowance of vitamin A is 900 μg per day for adult men and 700 for women, while that for vitamin D is 15 μg per day. The “Tolerable upper intake levels” are 3000 μg/day and 100 μg/day respectively, so people consuming cod liver oil as a source of omega-3 fatty acids should pay attention to how much vitamin A and vitamin D this adds to their diet.[8][9]
Cod liver oil may be an effective complementary measure for long-term treatment of multiple sclerosis.[10]
Use of cod liver oil during pregnancy is associated with lower risk of Type I diabetes in the offspring.[11] (although see adverse effects below). 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.
A Norwegian study of more than 68,000 women reported that female cancer patients who took daily cod-liver oil supplements had significantly reduced mortality (25% for all cancers, 45% for lung cancer) compared to women who did not take such supplements.[12][13]
Adverse effects
Per tablespoon (13.6g), cod liver oil contains 136% of the established daily Tolerable Upper Intake Level (UL) for Preformed Vitamin A (Retinol).[14][15] Vitamin A accumulates in body fat, and can reach harmful levels sufficient to cause hypervitaminosis A.[8] Pregnant women may want to consider consulting a doctor when taking cod liver oil because of the high amount of natural forms of vitamin A such as retinol. High doses of synthetic vitamin A (retinoids) have been shown to cause birth defects.[16] A toxic dose of retinol (vitamin A) is around 25 000 IU/kg (see Retinol#Retinoid overdose (toxicity)), or the equivalent of about 1.25 kg of cod liver oil for a 50-kg person.
The risks of hypervitaminosis and of exposure to environmental toxins such as mercury, polychlorinated biphenyls (PCBs), dioxins, and other contaminants, are reduced when purification processes are applied to produce refined fish-oil products, which consequently contain raised levels of omega-3 fatty acids, such as EPA and DHA.[17]
A high intake of cod liver oil by pregnant women is associated with a nearly fivefold increased risk of gestational hypertension,[18] although this study did not control for mercury, which can be present in harmful amounts in fish[17] and which is another cause of hypertension.[19]
Some urge caution when taking cod liver oil and other fish-based supplements since they may contain elevated levels of toxins such asmercury and PCBs found in fish.[17]
References
1. Rajakumar, K. Vitamin D, Cod-Liver Oil, Sunlight, and Rickets: A Historical Perspective. 2003. Pediatrics 112(2):132-1352.
2. Gruenwald J, Graubaum HJ, Harde A (2002). “Effect of cod liver oil on symptoms of rheumatoid arthritis”. Adv Ther 19 (2): 101–7.PMID 12069368.
3. 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.
4.von Schacky, C. (2000). “n-3 Fatty acids and the prevention of coronary atherosclerosis”. Am J Clin Nutr 71 ((1 Suppl)): 224S–7S.PMID 10617975.
5.Akpede, GO, et al.; Omotara, B.A.; Ambe, J.P. (1999). “Rickets and deprivation: a Nigerian study.”. J R.Soc.Health 119 (4): 216–22.doi:10.1177/146642409911900403.
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 (1): 15–20. doi:10.1080/02844310050160123.
7. a b Paul Lips (8 May 2003). “Hypervitaminosis A and fractures”. N Engl J Med 348 (4): 1927–1928. doi:10.1056/NEJMe020167.PMID 12540650. http://content.nejm.org/cgi/content/short/348/4/347. Retrieved 6 March 2008.
8.Haddad J.G. (30 April 1992). “Vitamin D — Solar Rays, the Milky Way, or Both?”. The New England Journal of Medicine.http://www.nejm.org/search q=vitamin+d&asug=Vitamin#qs=%3Fq%3D%2522too%2Bmuch%2Bvitamin%2Bd%2522%26date%3Dpast20Years. Retrieved 29 January 2012.
10. ^ Swank, Roy L., and Barbara Brewer Duggan. The Multiple Sclerosis Diet Book: A Low-Fat Diet for The Treatment of MS. Doubleday, 1987.
11. ^ Stene LC, Ulriksen J, Magnus P, Joner G (September 2000). “Use of cod liver oil during pregnancy associated with lower risk of Type I diabetes in the offspring”. Diabetologia 43 (9): 1093–8. doi:10.1007/s001250051499. PMID 11043854.
12. ^ Lund, Eiliv; Vanessa Dumeaux, Tonje Braaten, Anette Hjartåker, Dagrun Engeset, Guri Skeie, Merethe Kumle (6 June 2007). “Cohort Profile: The Norwegian Women and Cancer Study—NOWAC—Kvinner og kreft”. International Journal of Epidemiology (Oxford University Press) 2008 (37(1)): 36–41. doi:10.1093/ije/dym137. PMID 17644530. http://ije.oxfordjournals.org/cgi/content/full/37/1/36. Retrieved 12 October 2007.
13. ^ Skeie, G; Braaten T, Hjarta A, Brustad M, Lund E.. “Cod liver oil, other dietary supplements and survival among cancer patients with solid tumors.”. Int J Cancer 125: 1155–60. doi:10.1002/ijc.24422. PMID 19444919.
14. ^ National Nutrient Database for Standard Reference “USDA Nutrition Facts: Fish oil, cod liver” USDA
15. ^ Jane Higdon, Ph.D. of the Linus Pauling Institute “Linus Pauling Institute Micronutirent Center” Oregon State University
16. ^ Myhre AM, Carlsen MH, Bøhn SK, Wold HL, Laake P, Blomhoff R (December 2003). “Water-miscible, emulsified, and solid forms of retinol supplements are more toxic than oil-based preparations”. Am. J. Clin. Nutr. 78 (6): 1152–9. PMID 14668278.http://www.ajcn.org/cgi/pmidlookup?view=long&pmid=14668278.
17. ^ a b c Bays H E (19 March 2007). “Safety Considerations with Omega-3 Fatty Acid Therapy”. The American Journal of Cardiology. 99(Supplement 1) (6): S35–S43. doi:10.1016/j.amjcard.2006.11.020. PMID 17368277.
18. ^ Olafsdottir AS, Skuladottir GV, Thorsdottir I, Hauksson A, Thorgeirsdottir H, Steingrimsdottir L (March 2006). “Relationship between high consumption of marine fatty acids in early pregnancy and hypertensive disorders in pregnancy”. BJOG 113 (3): 301–9. doi:10.1111/j.1471-0528.2006.00826.x. PMID 16487202.
19. ^ Horowitz Y, Greenberg D, Ling G, Lifshitz (2002). “Acrodynia: a case report of two siblings”. Arch Dis Child 86 (6): 453.doi:10.1136/adc.86.6.453. PMC 1762992. PMID 12023189. //www.ncbi.nlm.nih.gov/pmc/articles/PMC1762992/.
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