Cod liver oil comes from the liver of cod fish. The popularity of this oil is due to its high omega-3 fatty acid content, specifically eicosapentaenoic acid and docosahexaenoic acid which have been linked to a number of health benefits. Supplementing with cod liver oil is especially useful for people who do not meet the American Heart Association's recommendation of eating at least two oily fish portions a week. A portion is 3.5 oz. of cooked fish.
Heart Health
Fish oil supplementation can reduce dysrhythmias, slightly lower blood pressure and decrease the rate of atherosclerosis. The protective effect of omega-3 oils on the cardiovascular system arises through a number of mechanisms. The March 2008 issue of "Expert Review of Cardiovascular Therapy" reports that these fatty acids interact with enzymes in the body and lead to a reduction in fats in the blood known as triglycerides. This is achieved through reduced secretion of triglycerides coupled with faster removal.
Inflammation
Both omega-3 and omega-6 fatty acids are essential, but most Western diets contain too much omega-6s compared with omega-3s. Omega-6s are pro-inflammatory while omega-3s are anti-inflammatory. Therefore, too large a ratio of omega-6 compared to omega-3 leads to an inflammatory state, which can exacerbate the symptoms of arthritis and inflammatory bowel diseases, as reported in the May 2010 issue of "Nutrition Reviews." Supplementing with cod liver oil is a way to normalize this ratio.
Cancer
Evidence is accumulating that omega-3 intake may help protect from cancer. The March 2011 issue of "International Journal of Cancer" reports a study that investigated the effect of several dietary components on breast cancer risk in 72,571 women. A significant association was found between marine omega-3s, and omega-6 intake on the risk of breast cancer -- the higher the intake of marine omega-3s, the lower the risk, while the higher the intake of omega-6, the higher the risk. The authors conclude that the ratio of omega-3:omega-6 consumption may be more important than the actual intakes.
Concerns
Cod liver oil, because it is derived from liver, is very high in vitamin A. Vitamin A is accumulated in the body and regular excessive consumption can be harmful. If you're pregnant, avoid vitamin A-containing supplements, and consult a doctor before taking cod liver oil. There is also some concern about mercury and other heavy metal and pesticide residues in cod liver oil, however the 2009 issue of "Neuro Endocrinology Letters" reports that none of the samples tested had contaminants above the safe levels.
References
- American Heart Association: Fish and Omega-3 Fatty Acids
- "Expert Review of Cardiovascular Therapy"; Prescription Omega-3 Fatty Acids and Their Lipid Effects: Physiologic Mechanisms of Action and Clinical Implications; H.E. Bays, et al.; March 2008
- "Nutrition Reviews"; Fatty Acids from Fish: the Anti-Inflammatory Potential of Long-Chain Omega-3 Fatty Acids; R. Wall, et al.; May 2010
- "International Journal of Cancer"; Dietary Polyunsaturated Fatty Acids and Breast Cancer Risk in Chinese Women: A Prospective Cohort Study; H.J. Murff, et al.; March 2011
- "Neuro Endocrinology Letters"; Fish Oil and Cod Liver as Safe and Healthy Food Supplements; M. Smutna, et al.; 2009
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