Fish oil, either eaten in fish or taken as a supplement, has proven benefits but also known risks. While fish oil may reduce triglyceride levels and reduce your risk of heart disease, fish oil can become contaminated by pollutants in the ocean and lakes. Some people should not take fish oil supplements because it may interfere with medication or worsen medical conditions. Before taking large amounts of fish oil, talk with your medical practitioner to determine the safety and proper dose for you.
Contamination
The oceans and lakes have, unfortunately, been contaminated with a number of pollutants potentially harmful to humans, including mercury, polychlorinated biphenyls, also known as PCBs and dioxin. Mercury accumulates more in the flesh of the fish than in the oil, the Mayo Clinic explains. Fish lowest in mercury include catfish, canned light tuna, pollock and salmon. Salmon and tuna are good sources of the omega-3 fatty acids found in fish oil, DHA and EPA. Fish high in mercury include king mackerel, shark, swordfish and tilefish. The risk of contamination is higher when you eat fish rather than take supplements. In Europe in 2000, dioxin levels in fish were eight times higher than dioxin levels in fish caught in less contaminated waters such as Chili and Peru, the Pacific Regional Aquaculture Information Service for Education reported. Pregnant women and children should avoid eating potentially fish at high risk for contamination.
Bleeding Issues
Fish oils can interfere with the ability of platelets to clump together and stop bleeding. This is particularly likely to occur in people taking more than 3 g of fish oil per day, according to the American Heart Association and in those taking blood-thinning medications or anticoagulants. People with disorders that increase bleeding or who take medications that increase bleeding should not take fish oil without their doctor's approval.
Intestinal Issues
Fish oil supplements can have a fishy aftertaste and can result in a fishy taste in the mouth after burping. High doses of fish oil can also cause severe diarrhea. Abdominal bloating, heartburn, acid reflux and abdominal pain can also occur. Taking supplements with meals and starting with a low dose and then increasing the amount may help avoid symptoms.
Vitamin E Effects
Taking large amounts of fish oil can cause a vitamin E deficiency, so many manufacturers add vitamin E to their supplements. This can cause excessive levels of vitamin E, a fat-soluble vitamin that is stored in the body.
Other Effects
Fish oil can increase low-density lipoprotein, the "bad" cholesterol, by 5 to 10 percent, according to MayoClinic.com. Fish oil supplement can also raise liver enzyme levels in rare cases. People with bipolar disorder should not take fish oil without taking first with their medical provider, since fish oil can increase mania symptoms. Because fish oil can lower blood pressure slightly, people taking blood pressure medications or those with low blood pressure should ask their medical practitioner before taking supplements.
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