Though they have their similarities, cod liver oil and fish oil supplements differ in notable ways. Both contain omega-3 fatty acids, offer numerous health benefits and may decrease the risk of depression and decrease depression symptoms. However, they differ in their constituent nutrients and also in possible contaminants, so there may be circumstances when you are better off choosing fish oil over cod liver oil.
Fish Oil and Cod Liver Oil Benefits
Omega-3 fatty acids in fish and cod liver oil lower triglycerides, lower blood pressure, reduce the risk of heart attacks, strokes, macular degeneration and certain types of cancer, and reduce symptoms of rheumatoid arthritis and lupus. Growing evidence also indicates that fish oil can improve drug-resistant depression, post partum depression and depression that occurs in bipolar disorder. Cod liver oil, too, is linked to decreased likelihood of depression. A 2007 Norwegian study published in the "Journal of Affective Disorders" examined symptoms of depression and anxiety in a national sample of 21,835 subjects. Those who used cod liver oil were 30 percent less likely to report having high levels of depressive symptoms.
Active Ingredient
The main ingredients in fish and cod liver oil that offer health benefits are the omega-3 fatty acids ecosapentaenoic acid and docosahexaenoic acid, also known as EPA and DHA respectively. Depressed patients tend to have low levels of EPA. EPA, but not DHA, has a therapeutic effect on depression, according to McManweb.com. Several studies found a therapeutic effect for EPA. For example, in his 2002 study published in the "Archives of General Psychiatry," Malcolm Peet found that patients who were not responding to antidepressants reported improvements in depression, anxiety, sleep, libido and suicidality following 12 weeks of supplementation with EPA. On the other hand, a report in the May 2003 "American Journal of Psychiatry" found no improvement in depression symptoms when only DHA was administered.
Mechanisms
Cell membranes are comprised chiefly of omega-3 oils. Your body converts omega-3 fatty acids into polyunsaturated fats, which play a role in allowing brain chemicals, such as serotonin, to pass into brain cells, according to Harvard researcher Andrew Stoll. Dr. Barry Sears describes several possible mechanisms for how EPA may improve depression symptoms. Serotonin in the frontal cortex of the brain regulates cognitive and emotional functioning. Consumption of EPA increases the amount of serotonin in the brain's frontal cortex. Omega-6 and omega-3 fatty acids compete for the same receptor sites. Depressed people tend to have more omega-6 relative to omega-3 fatty acids. When you increase EPA intake, you increase the omega-3 fatty acids in your blood lipids and in your cerebrospinal fluid. This inundates your brain with nutrients that not only enhance serotonin use, but also improve blood flow, which enhances the movement of oxygen and glucose into your brain.
Cod Liver Oil Versus Fish Oil
Though there are no studies that have done a direct comparison of their efficacy, fish oil might be more effective than cod liver oil for the treatment of depression. Fish oil tends to contain more EPA, while cod liver oil tends to be higher in DHA. The standard dosage of fatty acids in fish oil is 18 percent EPA and 12 percent DHA. Cod liver oil has more DHA and less EPA than fish oil, varying in EPA from 8 percent for Atlantic cod to 9 percent for Baltic cod. Cod liver oil has high amounts of vitamin A and D, and you can inadvertently consume more than is recommended by RDA standards. Also, cod liver oil is more likely to have contaminants because it is derived from the liver, the organ that filters out toxins. Women who are pregnant or breast feeding should not take cod liver oil, and should consult with their physicians about any supplements.
References
- "Archives of General Psychiatry"; A Dose-Ranging Study of the Effects of Ethyl-Eicosapentaenoate in Patients with Ongoing Depression Despite Apparently Adequate Treatment with Standard Drugs; Malcolm Peet, et al.; 2002
- BBC News: Cod Liver Oil 'Treats Depression'; June 13, 2007
- CBN.com; Omega 3 Fish Oils and Diet Help Alleviate Depression; Barry Sears, M.D.
- EVitamins: Fish Oil & Cod Liver Oil (EPA & DHA)
- "Journal of Affective Disorders"; Associations Between Cod Liver Oil Use and Symptoms of Depression: The Hordaland Health Study; M Raeder, et al.; August 2007
- "The American Journal of Psychiatry"; A Double-Blind, Placebo-Controlled Study of The Omega-3 Fatty Acid Docosahexaenoic Acid in the Treatment of Major Depression; Lauren Marangell, et al.; May 2003
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