For children in the 1930s and 1940s, taking your daily dose of cod liver oil was an important part of preventing rickets, if you could choke the stuff down. In addition to vitamin D, which prevents rickets, cod liver oil contains omega-3 fatty acids. Cod liver oil also contains large amounts of vitamin A, which can cause harm if taken in excessive quantities. Ask your doctor how much cod liver oil you should take and read labels carefully to make sure you're not exceeding the maximum doses of vitamins A and D.
Vitamin D
The vitamin D in cod liver oil varies from brand to brand. The Food and Nutrition Board currently recommends 600 IU of vitamin D per day between the ages of 1 and 70 and 800 IU per day for those 71 and over. For those over age 9, the maximum acceptable daily dose of vitamin D is 4,000; higher doses can cause high calcium levels, or hypercalcemia. Calcium deposits in the tissues and organs can damage the heart, kidneys and blood vessels.
Vitamin A
Cod liver oil, like other liver products, contains large amounts of vitamin A. Different cod liver oils contain varying amounts of vitamin A, which can cause toxicity, including birth defects during pregnancy, central nervous system disorders, liver problems or osteoporosis from low bone density. The recommended daily allowance, or RDA of vitamin A is 3,000 IU for males over age 14 and 2,300 IU for women. Doses over 10,000 IU of retinol, one of the active forms of vitamin A, can be toxic; to be on the safe side, do not exceed the RDA for vitamin A unless instructed to do so by your physician.
Omega-3 Fatty Acids
Like the oil of fatty fish such as salmon, cod liver oil contains omega-3 fatty acids eicosapentaenoic acid and docosahexaenoic acid, more commonly known as EPA and DHA. Omega-3 fatty acids have a number of benefits that can decrease your risk of heart disease, such as lowering cholesterol, reducing inflammation and preventing platelets from clumping together. However, cod liver oil contains less EPA and DHA than fish oils obtained from fish tissue. To get the therapeutic dose of omega-3 fatty acids from cod liver oil, you risk toxic doses of vitamin A and vitamin D, but the amount of omega-3 fatty acids varies from manufacturer to manufacturer. The recommended daily doses of DHA and EPA is 220 mg of each daily, the Oil of Pisces website states.
Vitamin E
Manufacturers may add vitamin E to cod liver oil and other fish oils to prevent spoilage and also to offset any vitamin E loss after long-term fish oil supplementation. Fish oil appears to deplete vitamin E in the body. A Tufts University study reported in the 1991 issue of "The Journal of Nutrition" found that vitamin E levels dropped after subjects took fish oil without added vitamin E for one month and dropped even further at the end of three months.
References
- Dr. Ben Kim; The Health Benefits of Cod Liver Oil and Fish Oil; Ben Kim, D.C.
- International Health News; Fish Oils: The Essential Nutrients; Hans R. Larsen, M.Sc.; July 2000
- Office of Dietary Supplements: Vitamin D
- "The Journal of Nutrition"; Effect of Long-Term Fish Oil Supplementation on Vitamin E Status and Lipid Peroxidation in Women; M. Metdani, et al.; 1991
- MedlinePlus; Fish Oil; February 2011
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