DOWNSIDE

Now that I have told you all this good news about cod liver oil, I need to comment on the research surrounding its possible toxicity. Over-elevated serum levels of vitamin D are a possibility if you combine summer or southern sun and cod liver oil. So if you are spending a lot of time out in the sun during the summer months, it's probably best to cut back on the dose. If you are unsure, you should test your blood levels of vitamin D.

Cod liver oil is no longer recommended in Great Britain and in the US pregnant women are advised to avoid most vitamin A and vitamin A-containing foods, including cod liver oil. Both countries have adopted this policy because of the recognized teratogenicity (may cause birth defects) of retinoic acid, a synthetic form of vitamin A. But low vitamin A also causes birth defects. In the developing countries, such as Brazil, Pakistan and India, vitamin A deficiency is widespread, afflicting millions. A 1992 survey of the US population determined that 50 percent of Americans consume 19 percent or less of the Recommended Daily Allowance (RDA) or 400 IU.

The original study showing birth defects associated with intake of mostly synthetic vitamin A exceeding 5,000 IU daily was published November 23, 1995 in the New England Journal of Medicine.46 Other studies showing an association of birth defects with vitamin A concerned topical creams containing vitamin A derivatives such as Accutane, or extremely high doses of A used in animal studies.^47-52

A later study, less well publicized, from the National Institute of Child Health and Human Development (NICHD), found no association with birth defects in women who took up to 10,000 IU of vitamin A during pregnancy. Because few women took more than 10,000 IU, researchers could not determine whether higher doses were a problem. Later Mills and others continued their research and determined that after serum testing and determining safe serum levels, women taking 30,000 IU of preformed vitamin A from animal foods (not beta-carotene) daily had the same blood levels of A as healthy pregnant women in the first trimester who had healthy babies. The conclusion is that a dosage over 30,000 IU vitamin A daily may be teratogenic for a certain few, but anything up to that amount is safe.^53-54

Thus if you are or may become pregnant, limit cod liver oil intake to not more than a total vitamin A value of 30,000 IU. If using my favorite brand, Carlson Labs cod liver oil, that would equal the amount of vitamin A found in 12 teaspoons or 4 tablespoons, more than anyone would ever take. If using high-vitamin cod liver oil, the limit would be 2 tablespoons. Two tablespoons of regular cod liver oil provide 15,000 IU vitamin A, 2600 IU vitamin D and 6 grams of mixed omega-3 fatty acids, safe for pregnancy and good for mom and baby.

There is one situation in which high levels of vitamin A are not recommended and that is the condition of certain types of liver disease in which there is altered vitamin A metabolism. This is frequently the case with alcoholism. Alcoholics should not take high doses (not more than 1-1.5 tablespoons of regular cod liver oil) and what they do take should be accompanied by zinc supplements. The enzymes needed for vitamin A metabolism in the liver are zinc dependent.

The most likely culprits for production of birth defects in humans are topical and oral vitamin A analogs, not cod liver oil. Researchers have criticized the original 1995 study, from which governmental policy has been derived, for overstating the negative effect. Only 1.4 percent took supplements exceeding 10,000 IU a day, not a large enough sample from which to draw conclusions. However, it is important to never combine cod liver oil or vitamin A from supplements with oral or topical medications for acne or other skin disorders treated with retinoic acid derivatives.

If you sunbathe regularly and have found that your vitamin D levels are within the normal range, do not use cod liver oil unless you are willing to test and retest to determine that your blood levels of vitamin D have not gone too high. We do not know enough to say whether or not sunbathing and cod liver oil work synergistically or antagonistically. If you decide to get lots of sun and also use cod liver oil, please send me your vitamin D tests for my continued research. Cod liver oil use is safe in most of the US and all of Canada in winter but it should not be combined with other sources of vitamin D without careful testing and monitoring.

PRICE WAS RIGHT

Dr. Price was right. . . we all need to take cod liver oil (and eat plenty of good butter). For growing children, and for almost every disease condition, cod liver oil is the number one superfood, the supplement of choice.

REFERENCES

1. Aviram M, Brox J, Nordoy A. Acute effects of dietary cod liver oil and cream on plasma lipoproteins. Ann.Nutr Metab 1986;30:143-8.
   
2. Brox JH, Killie JE, Gunnes S, Nordoy A. The effect of cod liver oil and corn oil on platelets and vessel wall in man. Thromb.Haemost. 1981;46:604-11.
   
3. Brox JH, Killie JE, Osterud B, Holme S, Nordoy A. Effects of cod liver oil on platelets and coagulation in familial hypercholesterolemia (type IIa). Acta Med.Scand. 1983;213:137-44.
   
4. Vognild E, Elvevoll EO, Brox J et al. Effects of dietary marine oils and olive oil on fatty acid composition, platelet membrane fluidity, platelet responses, and serum lipids in healthy humans. Lipids 1998;33:427-36.
   
5. Aviram M, Brox J, Nordoy A. Effects of postprandial plasma and chylomicrons on endothelial cells. Differences between dietary cream and cod liver oil. Acta Med.Scand. 1986;219:341-8.
   
6. Brox J, Olaussen K, Osterud B et al. A long-term seal- and cod liver oil supplementation in hypercholesterolemic subjects. Lipids 2001;36:7-13.
   
7. Skuladottir GV, Gudmundsdottir E, Olafsdottir E et al. Influence of dietary cod liver oil on fatty acid composition of plasma lipids in human male subjects after myocardial infarction. J Intern.Med. 1990;228:563-8.
   
8. Schmidt EB, Pedersen JO, Ekelund S, Grunnet N, Jersild C, Dyerberg J. Cod liver oil inhibits neutrophil and monocyte chemotaxis in healthy males. Atherosclerosis 1989;77:53-7.
   
9. Shimokawa H, Vanhoutte PM. Dietary cod liver oil improves endothelium-dependent responses in hypercholesterolemic and atherosclerotic porcine coronary arteries. Circulation 1988;78:1421-30.
   
10. Shimokawa H, Lam JY, Chesebro JH, Bowie EJ, Vanhoutte PM. Effects of dietary supplementation with cod liver oil on endothelium-dependent responses in porcine coronary arteries. Circulation 1987;76:898-905.
    
11. Burchard HU, Tischendorf FW. The effects of the intake of cod liver oil on the blood lipid level, the lipoprotein profile and bleeding time. Z.Ernahrungswiss. 1989;28:84-91.
    
12. Gudbjarnason S. Dynamics of n-3 and n-6 fatty acids in phospholipids of heart muscle. J Intern.Med.Suppl 1989;225:117-28.
    
13. Gudbjarnason S, Benediktsdottir VE, Skuladottir G. Effects of n-3 polyunsaturated fatty acids on coronary heart disease. Bibl.Nutr Dieta 1989;1-12.
    
14. Gudbjarnason S, Oskarsdottir G. Modification of fatty acid composition of rat heart lipids by feeding cod liver oil. Biochim.Biophys.Acta 1977;487:10-5.
    
15. Benediktsdottir VE, Gudbjarnason S. Modification of the fatty acid composition of rat heart sarcolemma with dietary cod liver oil, corn oil or butter. J Mol.Cell Cardiol. 1988;20:141-7.
    
16. Akpede GO, Omotara BA, Ambe JP. Rickets and deprivation: a Nigerian study. J R.Soc.Health 1999;119:216-22.
    
17. Wilton P. Cod liver oil, vitamin D and the fight against rickets. CMAJ. 1995;152:1516-7.
    
18. Requirand P, Gibert P, Tramini P, Cristol JP, Descomps B. Serum fatty acid imbalance in bone loss: example with periodontal disease. Clin Nutr 2000;19:271-6.
    
19. Watkins BA, Lippman HE, Le Bouteiller L, Li Y, Seifert MF. Bioactive fatty acids: role in bone biology and bone cell function. Prog.Lipid Res. 2001;40:125-48.
    
20. Sigurdsson G, Franzson L, Steingrimsdottir L, Sigvaldason H. The association between parathyroid hormone, vitamin D and bone mineral density in 70-year-old Icelandic women. Osteoporos.Int. 2000;11:1031-5.
    
21. Stene LC, Ulriksen J, Magnus P, Joner G. Use of cod liver oil during pregnancy associated with lower risk of Type I diabetes in the offspring. Diabetologia 2000;43:1093-8.
    
22. Seip M. [Infant nutrition in Norway in the light of recent research]. Tidsskr.Nor Laegeforen. 1991;111:2122-5.
    
23. Tsutsumi K, Obata Y, Takayama K, Loftsson T, Nagai T. Effect of cod liver oil extract on the buccal permeation of ergotamine tartrate. Drug Dev.Ind.Pharm. 1998;24:757-62.
    
24. Olafsdottir AS, Wagner KH, Thorsdottir I, Elmadfa I. Fat-Soluble Vitamins in the Maternal Diet, Influence of Cod liver oil Supplementation and Impact of the Maternal Diet on Human Milk Composition. Ann.Nutr Metab 2001;45:265-72.
    
25. Semba RD. Vitamin A as "anti-infective" therapy, 1920-1940. J Nutr 1999;129:783-91.
    
26. Lombardo YB, Chicco A, D'Alessandro ME, Martinelli M, Soria A, Gutman R. Dietary fish oil normalize dyslipidemia and glucose intolerance with unchanged insulin levels in rats fed a high sucrose diet. Biochim.Biophys.Acta 1996;1299:175-82.
    
27. Chicco A, D'Alessandro ME, Karabatas L, Gutman R, Lombardo YB. Effect of moderate levels of dietary fish oil on insulin secretion and sensitivity, and pancreas insulin content in normal rats. Ann.Nutr Metab 1996;40:61-70.
    
28. Shimizu H, Ohtani K, Tanaka Y, Sato N, Mori M, Shimomura Y. Long-term effect of eicosapentaenoic acid ethyl (EPA-E) on albuminuria of non-insulin dependent diabetic patients. Diabetes Res.Clin Pract. 1995;28:35-40.
    
29. Jensen T, Stender S, Goldstein K, Holmer G, Deckert T. Partial normalization by dietary cod liver oil of increased microvascular albumin leakage in patients with insulin-dependent diabetes and albuminuria. N.Engl.J Med. 1989;321:1572-7.
    
30. Schimke E, Hildebrandt R, Beitz J et al. Influence of a cod liver oil diet in diabetics type I on fatty acid patterns and platelet aggregation. Biomed.Biochim.Acta 1984;43:S351-S353.
    
31. Beitz J, Schimke E, Liebaug U et al. Influence of a cod liver oil diet in healthy and insulin-dependent diabetic volunteers on fatty acid pattern, inhibition of prostacyclin formation by low density lipoprotein (LDL) and platelet thromboxane. Klin.Wochenschr. 1986;64:793-9.
    
32. Codde JP, McGowan HM, Vandongen R, Beilin LJ. Changes in prostanoid synthesis in response to diet and hypertension in one-kidney, one clip rats. Hypertension 1985;7:886-92.
    
33. Codde JP, Beilin LJ. Dietary fish oil prevents dexamethasone induced hypertension in the rat. Clin Sci.(Lond) 1985;69:691-9.
    
34. Moritz V, Singer P, Forster D, Berger I, Massow S. Changes of blood pressure in spontaneously hypertensive rats dependent on the quantity and quality of fat intake. Biomed.Biochim.Acta 1985;44:1491-505.
    
35. Singer P, Berger I, Gerhard U, Wirth M, Moritz V, Forster D. Changes of N-6 and N-3 fatty acids in spontaneously hypertensive (SHR) and normotensive rats after diets supplemented with alpha-linolenic or eicosapentaenoic acids. Prostaglandins Leukot.Med. 1987;28:183-93.
    
36. Mancino M, Ohia E, Kulkarni P. A comparative study between cod liver oil and liquid lard intake on intraocular pressure on rabbits. Prostaglandins Leukot.Essent.Fatty Acids 1992;45:239-43.
    
37. Vilaseca J, Salas A, Guarner F, Rodriguez R, Martinez M, Malagelada JR. Dietary fish oil reduces progression of chronic inflammatory lesions in a rat model of granulomatous colitis. Gut 1990;31:539-44.
    
38. Guarner F, Vilaseca J, Malagelada JR. Dietary manipulation in experimental inflammatory bowel disease. Agents Actions 1992;Spec No:C10-C14.
    
39. Terkelsen LH, Eskild-Jensen A, Kjeldsen H, Barker JH, Hjortdal VE. Topical application of cod liver oil ointment accelerates wound healing: an experimental study in wounds in the ears of hairless mice. Scand.J Plast.Reconstr.Surg.Hand Surg. 2000;34:15-20.
    
40. Eriksen W, Sandvik L, Bruusgaard D. Does dietary supplementation of cod liver oil mitigate musculoskeletal pain? Eur.J Clin Nutr 1996;50:689-93.
    
41. Lips P. Vitamin D deficiency in a multicultural setting. Ned.Tijdschr.Geneeskd. 2001;145:2060-2.
    
42. Simonsen T, Nordoy A, Sjunneskog C, Lyngmo V. The effect of cod liver oil in two populations with low and high intake of dietary fish. Acta Med.Scand. 1988;223:491-8.
    
43. Simonsen T, Nordoy A. Ischaemic heart disease, serum lipids and platelets in Norwegian populations with traditionally low or high fish consumption. J Intern.Med.Suppl 1989;225:83-9.
    
44. Luley C, Klein B, Hanisch M, Prellwitz W. Fatty acid composition and degree of peroxidation in fish oil and cod liver oil preparations.Arzneimittel-forschung. 1988;38:1783-6.
    
45. Bjerve KS. n-3 fatty acid deficiency in man. J Intern.Med.Suppl 1989;225:171-5.
    
46. Rothman KJ, Moore LL, Singer MR, Nguyen US, Mannino S, Milunsky A. Teratogenicity of high vitamin A intake. N.Engl.J Med. 1995;333:1369-73.
    
47. Orfanos CE, Zouboulis CC, Almond-Roesler B, Geilen CC. Current use and future potential role of retinoids in dermatology. Drugs 1997;53:358-88.
    
48. Die-Smulders CE, Sturkenboom MC, Veraart J, van Katwijk C, Sastrowijoto P, van der LE. Severe limb defects and craniofacial anomalies in a fetus conceived during acitretin therapy. Teratology 1995;52:215-9.
    
49. Mills CM, Marks R. Adverse reactions to oral retinoids. An update. Drug Saf 1993;9:280-90.
    
50. Heckel S, Favre R, Weber P, Dellenbach P. [Teratogenicity of retinoids. A case and review of the literature]. J Gynecol.Obstet.Biol.Reprod.(Paris) 1993;22:43-7.
    
51. Nau H. Embryotoxicity and teratogenicity of topical retinoic acid. Skin Pharmacol. 1993;6 Suppl 1:35-44.
    
52. Pinnock CB, Alderman CP. The potential for teratogenicity of vitamin A and its congeners. Med.J Aust. 1992;157:804-9.
    
53. Miller RK, Hendrickx AG, Mills JL, Hummler H, Wiegand UW. Periconceptional vitamin A use: how much is teratogenic? Reprod.Toxicol. 1998;12:75-88.
    
54. Wiegand UW, Hartmann S, Hummler H. Safety of vitamin A: recent results. Int.J Vitam.Nutr Res. 1998;68:411-6.
    
55. Knapp HR and others. The Effect of Cod liver oil on the Development of Atherosclerosis in an Animal Model. Proceedings of the AOCS, Ed WEM Lands, AOCS 1987, pp 35-40.
    
56. http://www.animalrights.net/print/articles/2002/000068.html
    
57. Shu XO and others. A population-based case-control study of childhood leukemia in Shanghai. Cancer 1988 Aug 1;62(3):635-44.
    
58. Veierod MG, Laake P, Thelle DS. Dietary fat intake and risk of lung cancer: a prospective study of 51,452 Norwegian men and women. Eur J Cancer Prev 1997 Dec;6(6):540-9.