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LetterCorrespondence
Robert C. Oh
The Journal of the American Board of Family Practice September 2005, 18 (5) 446; DOI: https://doi.org/10.3122/jabfm.18.5.446
Robert C. Oh
MD
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To the Editor: I thank Ms. Ross for the comments on my article. I too feel strongly that physicians under-appreciate and under-recognize mild vitamin D deficiency.1 Although cod liver oil is rich in vitamin D, most formulations do not have enough omega-3 fatty acids (FA) for it to be practical in clinical use. In an informal survey I performed, I found that typical preparations contain approximately 50 to 90 mg of omega-3 FA (compared with 300 mg in fish oil).2 To reach 1 to 4 g of omega-3 FA (doses needed for secondary prevention of cardiovascular disease, rheumatoid arthritis, and hypertriglyceridemia)2 one would have to ingest 10 to 40 capsules of cod liver oil daily.

In addition, cod liver oil contains approximately 135 IU of vitamin D and 2500 IU of vitamin A in each capsule. Toxic doses of vitamin A can occur if cod liver oil is given in doses typical for treatment of hypertriglyceridemia and rheumatoid arthritis (2 to 4 g). Studies have also linked chronic daily vitamin A intake to increased fracture risk and teratogenicity.3–5 Cod liver oil may potentially be used for conditions requiring supplementation of vitamin A and D but should generally be avoided for conditions requiring high levels of omega-3 FA. Other formulations may contain higher levels of omega-3 FA, but consumers and physicians must be especially cognizant of the amount of vitamin D and vitamin A that are contained in the preparation to avoid toxicity.

Even typical fish oil supplements may be difficult to provide 2 to 3 g of omega-3 FA, and physicians should consider prescribing highly concentrated formulations. Recently, the Food and Drug Administration has approved a prescription form of omega-3 FA containing approximately 900 mg of omega-3 FA in each capsule.6 Although only approved for the treatment of hypertriglyceridemia, physicians can also consider this formulation in off-label uses for secondary prevention of cardiovascular disease and rheumatoid arthritis to minimize the number of capsules that patients have to take.

References

  1. ↵
    Oh R. Vitamin D insufficiency as a cause of hyperparathyroidism. Am Fam Physician 2005; 71: 46,49.
    OpenUrlPubMed
  2. ↵
    Oh R. Practical applications of fish oil (omega-3 fatty acids) in primary care. J Am Board Fam Pract 2005; 18: 28–36.
    OpenUrlAbstract/FREE Full Text
  3. ↵
    Feskanich D, Singh V, Willett WC, Colditz GA. Vitamin A intake and hip fractures among postmenopausal women. JAMA 2002; 287: 47–54.
    OpenUrlCrossRefPubMed
  4. Michaelsson K, Lithell H, Vessby B, Melhus H. Serum retinol levels and the risk of fracture. N Engl J Med 2003; 348: 287–94.
    OpenUrlCrossRefPubMed
  5. Rothman KJ, Moore LL, Singer MR, et al. Teratogenicity of high vitamin A intake. N Engl J Med 1995; 333: 1369–73.
    OpenUrlCrossRefPubMed
  6. ↵
    Omacor. Consumer drug information sheet. U.S. Food and Drug Administration. Accessed on July 4, 2005 at: http://www.fda.gov/cder/consumerinfo/druginfo/omacor.htm
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The Journal of the American Board of Family Practice: 18 (5)
The Journal of the American Board of Family Practice
Vol. 18, Issue 5
1 Sep 2005
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Robert C. Oh
The Journal of the American Board of Family Practice Sep 2005, 18 (5) 446; DOI: 10.3122/jabfm.18.5.446

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The Journal of the American Board of Family Practice Sep 2005, 18 (5) 446; DOI: 10.3122/jabfm.18.5.446
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