Flaxseed oil and cod liver oil are two significant sources of omega-3 fatty acids, which are known to be essential for child development and human health. They are, however, two very different sources of these substances. Flaxseed oil comes from a plant source and fish oil from an animal source. Other differences include the types of omega-3 fatty acids they contain and the health risks associated with each.
Omega-3 Fatty Acids
Cod liver oil contains two omega-3 fats called docosahexaenoic acid, or DHA, and eicosapentaenoic acid, or EPA, while flaxseed oil contains a different omega-3 fat called alpha-linolenic acid, or ALA. The body needs all three of these fatty acids for different purposes. The body can convert the ALA in flaxseed oil into EPA and DHA, though in much smaller quantities than the same amount cod liver oil naturally contains. Cod liver oil, however, does not contain ALA nor the resources for the body to produce it.
Cod Liver Oil Benefits
In a study published in "Cardiovascular Research" in 2009, researchers found that the omega-3 polyunsaturated fatty acids in fish oils, like cod liver oil, helped reduce occurrences of heart failure, whereas those in flaxseed oil did not. They further found that dietary supplementation with fish oil but not flaxseed oil suppressed inflammation and prevented certain kinds of heart failure. Fish oil also increased production of a blood hormone that helps burn fat and suppress appetite, while flax oil does not. Unlike other fish oils, cod liver oil in particular is a significant source of vitamins A and D.
Flaxseed Oil Benefits
In a 2007 "Journal of the Society of Integrative Oncology" research review, flaxseed was studied for its potential benefits in at least 13 different categories of medical disorders, including ADHD, constipation and diarrhea, breast cancer, menopause, atherosclerosis, HIV/AIDS, hypertension, diabetes and prostate cancer. None of these studies, however, has yielded sufficient evidence to support a medical recommendation of flaxseed oil for any of these conditions.
Adverse Effects
Large doses of flaxseed oil have been associated with diarrhea and loose stools. Allergic reactions and cases of anaphylaxis have also occurred from flaxseed oil consumption. Cod liver oil poses certain health risks that other forms of fish oil do not. Coming from the fish's liver as opposed to the body, as in other fish oils, cod liver oil contains potentially excessive amounts of vitamin A in the form of retinol, which can be toxic in high enough doses and has been associated with a variety of health risks, including liver problems, lowered bone density and birth defects.
References
- "Cardiovascular Research"; Fish Oil, but Not Flaxseed Oil, Decreases Inflammation...; M.K. Duda, et al.; February 2009
- "Journal of the Society of Integrative Oncology"; Flax And Flaxseed Oil; E. Basch, et al.; 2007
- "Rheumatology International"; Alpha-Linoleic Acid in the Treatment of Rheumatoid Arthritis...; D.C. Nordstrom, et al.; 1995
- "Journal Of Allergy And Clinical Immunology"; Anaphylaxis Caused by Linseed (Flaxseed) Intake; L. Alonso, et al.; 1996
- National Institutes of Health: Dietary Supplement Fact Sheet - Vitamin A and Carotenoids
- Harvard Medical School Family Health Guide; Why Not Flaxseed Oil?; November 2006
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