Omega-3 fatty acids are touted for their anti-inflammatory benefits, helping you fight off conditions from heart disease to high blood pressure to osteoporosis. While eating regular servings of fish can help you get omega-3 fatty acids in your daily diet, consuming too much fish can increase your mercury intake. Another option is to take a daily cod liver oil supplement, which contains omega-3 fatty acids as well. Because cod livers are responsible for filtering nutrients and toxins, concerns have been raised about the mercury levels present in supplements.
Fish Used
Because some types of fish contain more mercury, fish oil manufacturers tend to use low-mercury fish such as cod. Fish such as shark, king mackerel or farm-raised salmon tend to have more mercury because they live longer and can collect more mercury throughout their lifetimes. These fish also can boost their levels by feeding on smaller fish that contain mercury. Because cod feed on algae and plant material, they tend to have less mercury to begin with, which can be advantageous in the manufacturing process.
Filtration Processes
In addition to the type of fish used, manufacturers use several mercury purification processes. In the case of cod liver oil, the cod livers are separated from fish and ground. They are then put through both a centrifuge and heating process, which separates the oil from the toxins. The cod liver oil is then removed and deodorized before it is placed into tablets. After these processes, the fish oil supplements should be free from mercury and other contaminants.
Research
The UK Food Standards Agency -- similar to the U.S. Food & Drug Administration -- tested 100 samples of fish oil supplements, ranging from salmon oil to shark oil. The survey sampled 26 cod liver oil products and 19 high-strength cod liver oil products. The samples were then tested for detectable mercury levels, which were defined as 0.0014 mg/kg. The researchers found nine of the samples contained mercury levels above the range of detection. Four of these supplements were cod liver oil types. Also, the researchers found you would have to take 500 tablets per day in addition to the possible mercury in the foods you eat to exceed the provisional tolerable weekly intake limit of 0.23 mg per kg of body weight.
Recommendations
While you cannot tell the level of mercury in your cod liver oil pills simply by eying them, you can purchase fish oil capsules that a third party has tested. International agencies such as the World Health Organization, International Fish Oil Standards and Council for Responsible Nutrition all test cod liver oil capsules. The cod liver oil pills should bear a label that indicates the pills have been third-party tested. Also, it is important to take the recommended safe dosages for cod liver oil.
References
- MedlinePlus; Fish Oil; February 2011
- UK Food Standards Agency; Survery of Mercury in Fish Oil Supplements; October 2005
- "The New York Times"; The Claim - Fish Oil Supplements Can Contain Mercury; Anahad O'Connor; March 2009
- "Whole Living"; Is Fish Oil Safe?; April 2008
- "Whole Living"; Is Your Fish Oil Safe?; Olessa Pindak; January 2011
- UC Berkeley Wellness Guide to Dietary Supplements; Cod Liver Oil; 2011
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