When you take cod liver oil, you gain vitamins A and D, which help you maintain a healthy immune system as well as healthy skin, bones and eyes. Cod liver and other fish oil supplements also provide omega-3 fatty acids, which help counter inflammation. Cod liver oil is promoted for many uses, from lowering triglycerides to improving arthritis symptoms to preventing migraines. Scientific evidence backs some, but not all, such uses. Cod liver oil also can cause side effects and interact with medicine, so check with a doctor before trying a cod liver oil supplement.
Triglycerides
Cod liver and other fish oil supplements are effective against high triglycerides, which are associated with heart disease, according to MedlinePlus, the National Institutes of Health's medical information website. In fact, fish oil may be able to reduce triglycerides by 20 to 50 percent due to its omega-3 fatty acid content, adds MedlinePlus. One study that demonstrates cod liver's triglyceride-lowering effect is published in the 1989 German nutritional sciences journal "Zeitschrift für Ernährungswissenschaft." Study subjects who took 4 g daily for six months significantly lowered their triglycerides. The effect on triglycerides is dose-dependent, notes a 2011 study published in the "American Journal of Clinical Nutrition." The study found that .85 g omega-3 fatty acids had no effect on triglycerides, whereas 3.4 g per day lowered triglycerides by 27 percent compared to a placebo, according to lead study author A.C. Skulas-Ray.
Heart Disease
If you have a healthy heart, cod liver and other fish oils are classified as likely effective for helping you prevent heart disease by the National Institutes of Health. Also, if you already have heart disease, cod liver oil may lower your risk of dying from it. In fact, fish oil may even work better than the cholesterol-lowering drugs called statins for this purpose, according to MedlinePlus. One study published in the December 2007 "Journal of Pharmacy and Pharmacology" found that cod liver oil specifically may prevent cardiovascular disorders that are associated with diabetes due to its omega-3 fatty acid content as well as its antioxidant vitamin A content, according to lead study author A. Ceylan-Isik.
Arthritis and Other Conditions
Due to its omega-3 fatty acid content, cod liver oil may help alleviate the pain and joint stiffness associated with arthritis, according to University of California at Berkeley. A 2002 study published in "Advances in Therapy" found that taking 1 g cod liver oil daily may help relieve your morning stiffness, swollen joints and pain intensity if you have rheumatoid arthritis. Still, more study is needed. The National Institutes of Health classifies fish oils like cod liver as "possibly effective," as opposed to "likely effective" or "effective." Other uses classified as possibly effective for cod liver and other fish oil supplements include high blood pressure, menstrual pain, lowering stroke risk, osteoporosis, high cholesterol, bipolar disorder, the cold tolerance problem called Raynaud's syndrome, age-related eye disease, psoraisis and attention deficit-hyperactivity disorder. According to MedlinePlus, it is unlikely effective against migraines, muscle soreness from exercise, stomach ulcers, liver disease and gingivitis. There's insufficient evidence to rate it as effective or ineffective for a host of other conditions, including cancer, Alzheimer's, dermatitis and mental health conditions.
Side Effects and Other Considerations
Cod liver oil can cause nausea in some people. It also may cause an allergic reaction. Contact a doctor immediately if you experience allergy symptoms like hives, itching, a swollen face or hands, mouth or throat swelling, trouble breathing, or chest tightness. Cod liver oil can interact with blood-thinning medications like aspirin and warfarin and may worsen your condition if you have a bleeding disorder. It also may interact with hormone medications. Taking too much cod liver oil can lead to vitamin A toxicity due to the oil's high content of this vitamin. Use caution especially if you consume many foods that also have vitamin A or take vitamin supplements. Too much vitamin A can weaken bones, raise the risk for fractures and cause birth defects. Some cod liver oil supplements with reduced vitamin A are available.
Because this oil is made from the liver, which act as the body's filter for toxins, there's concern about contaminants like PCBs, according to the University of California at Berkeley. If you have heart disease, kidney stones, liver disease, sarcoidosis or overactive parathyroid, consult a doctor before using cod liver oil. Also consult a doctor if you are pregnant and considering using this oil.
References
- University of California at Berkeley: Wellness Guide to Dietary Supplements
- MedlinePlus: Fish Oil
- "Advances in Therapy"; Effect of Cod Liver Oil on Symptoms of Rheumatoid Arthritis; J. Gruenwald, et al.; 2002
- "Zeitschrift für Ernährungswissenschaft"; The Effects of the Intake of Cod Liver Oil on the Blood Lipid Level, the Lipoprotein Profile and Bleeding Time; H.U. Burchard and F.W. Tischendorf; 1989
- "American Journal of Clinical Nutrition"; Dose-Response Effects of Omega-3 Fatty Acids on Triglycerides, Inflammation and Endothelial Function in Healthy Persons With Moderate Hypertriglyceridemia; A.C. Skulas-Ray, et al.; 2011
- "The Journal of Pharmacy and Pharmacology"; Cod Liver Oil Supplementation Improves Cardiovascular and Metabolic Abnormalities in Streptozotocin Diabetic Rats; A. Ceylan-Isik, et al.; 2007
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