Cod liver oil is a health supplement extracted from the liver of cod fish. Fatty fishes, such as cod, contain high levels of beneficial omega-3 fatty acids, and fish oils like cod liver oil are a rich source of these compounds. Although cod liver oil is available over the counter and is generally safe and well-tolerated, it may cause side effects, especially when taken in high doses. As with any health supplement, you should consult your doctor before taking cod liver oil.
General Side Effects
Cod liver oil supplements may potentially cause several non-specific side effects, including nausea, nosebleeds, heartburn and rash. A frequent complaint of people taking cod liver oil is the occurrence of "fishy" burps, leading to bad breath. Cod liver oil can also cause gastrointestinal effects, including loose stools and diarrhea. Freezing the cod liver oil supplements or taking them immediately after a meal may reduce the risk of these side effects.
Potentially Dangerous Side Effects
In certain situations, more dangerous side effects may result from cod liver oil. High doses of cod liver oil, such as 3 g or more per day, can potentially inhibit the immune system, increasing the risk of infections. People who are immune-compromised, such as the elderly and HIV/AIDS patients, should take extra caution with cod liver oil supplements, warns MedlinePlus. Cod liver oil has also been reported to alter the balance of cholesterol in the body, raising levels of low-density lipoprotein cholesterol, also known as LDL or "bad" cholesterol.
Drug Interactions
Doses of greater than 3 g per day of cod liver oil can reduce the ability of blood to clot, which increases the risk of serious bleeding. This effect is particularly dangerous for people taking blood-thinning medications, such as warfarin, to treat blood clots. Cod liver oil can also potentially lower blood pressure. If cod liver oil supplements are taken at the same time as prescription medications that treat high blood pressure, blood pressure may drop to dangerously low levels. If you are given a prescription for medications that prevent clotting or lower blood pressure, be sure to tell your doctor if you are taking cod liver oil.
Mercury Contamination
Fish may be contaminated with potentially toxic levels of environmental pollutants, such as mercury, dioxins and polychlorinated biphenyls. These pollutants may be concentrated in fish oils such as cod liver oil. When choosing a brand of cod liver oil, look on the label for a purification process, such as molecular distillation, which removes these toxic pollutants, recommends the Creighton University Medical Center.
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