Cod liver oil and fish oil both provide omega-3 fatty acids and so potentially provide numerous physical, emotional and behavioral health benefits. However, they also differ in ways that make one better than the other, depending on your particular condition or purpose. They differ in the level of additional vitamins, the amount of active ingredients and the potential amount of contaminants and toxins.
Active Ingredients
Both cod liver oil and fish oil contain two omega-3 fatty acids, DHA and EPA, which promote anti-inflammatory responses from your immune system. Western diets provide 14 to 25 times the amount of omega-6 fatty acids as omega-3 fatty acids, creating a relative excess of omega-6 fatty acids, according to the journal "Biomedicine & Pharmacotherapie." The deficiency of omega-3 fatty acids promotes excessive inflammatory reactions, which in turn contribute to a variety of diseases and conditions, reports researcher Philip Calder in the June 2006 "American Journal of Clinical Nutrition."
Additional Nutrients in Cod Liver Oil
Unlike fish oil, cod liver oil provides vitamins A and D. Vitamin A contributes to the health and maintenance of your teeth, skin, eyes, skeleton and soft tissues. A deficiency of vitamin A leaves you vulnerable to infectious diseases and vision problems. With the exception of foods that are fortified, such as milk or cereal, few foods provide vitamin D. Vitamin D allows absorption of calcium in the gut and helps strengthen bones by maintaining serum levels of calcium and phosphates. Breastfed infants, older adults, people with limited sun exposure, people with fat malabsorption and people with dark skin are at greatest risk of vitamin D deficiency.
Contaminants
Cod liver oil, derived from the liver of cod, might be more vulnerable to contamination with PCBs, mercury and other toxins than fish oil. Fish oil is derived from the flesh of fish, which contains fewer contaminants than the liver, an organ that filters out and then retains certain contaminants. Large, predatory fish and fish that have longer lives, such as cod, accumulate a greater amount of toxins than small, short-lived fish. A lawsuit filed in 2010 identified 10 fish or cod liver oil products that allegedly contain dangerous levels of polychlorinated biphenyl compounds, or PCBs. Eight of the 10 products were liver oils. One of the remaining two products was manufactured from salmon.
Dosage
The recommended therapeutic dose of omega-3 fatty acids depends on the reason you're taking an EPA/DHA supplement and the severity of your condition. Fish oil contains a higher concentration of EPA and DHA. Cod liver oil generally contains about 10 percent EPA and DHA, while standard fish oil has 30 percent EPA and DHA. Concentrated fish oil has as much as 60 percent EPA and DHA. You'd have to take three to six times as many cod liver oil capsules to obtain the equivalent amount of EPA and DHA contained in a single 1-g fish oil capsule.
When Fish Oil Is Better
If you are pregnant or breastfeeding or are giving the supplement to a young child, use fish oil rather than cod liver oil. If you are treating a condition that requires a larger dosage of EPA or DHA, again, stick to fish oil over cod liver oil. For example, to reduce inflammation and pain associated with rheumatoid arthritis, rheumatologist Leslie Cleland recommends 2.7 g or more of omega-3 fatty acids. You would have to take 27 1-g capsules of cod liver oil to obtain therapeutic levels of EPA and DHA. This amount of cod liver oil would provide you with vitamin A and D significantly in excess of daily recommended amounts, and it could lead to vitamin overdoses over time, as fat-soluble vitamins accumulate in your body fat.
References
- "Arthritis Research & Therapy"; Fish Oil: What the Prescriber Needs to Know; Leslie Cleland, et al.; 2006
- "Biomedicine & Pharmacotherapie"; The Importance of the Ratio of Omega-6/Omega-3 Essential Fatty Acids; Artemis Simopoulos; October 2002
- MedlinePlus: Vitamin A
- Mercury News: Lawsuit Claims PCBs Found in 10 Fish Oil Supplements; Product Labeling Sought
- Office of Dietary Supplements: Vitamin D
- "The American Journal of Nutrition"; n-3 Polyunsaturated Fatty Acids, Inflammation, and Inflammatory Diseases; Philip Calder; June 2006
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