Fish oil takes the form of omega-3 fatty acids. This is one of the healthiest fats, beneficial to the immune system and brain development. Unfortunately, fish also tends to contain trace amounts of mercury, including the oily parts. At low levels, mercury is not necessarily toxic. Humans have some mercury in their tissues, but it is harmful in larger quantities, which makes avoidance of mercury critical.
Definition
Mercury is a type of metal that remains liquid at room temperature. It occurs naturally in the environment and can also be released through industrial pollution. Mercury is toxic in large enough doses, dramatically affecting the nervous system, and has been phased out of many consumer products, such as batteries. If it accumulates in the water, it can transform into methyl mercury, which is the form that it usually takes within fish.
Significance
Mercury is typically promulgated in fish that are either at the top of the food chain, where it accumulates and builds from the consumption of other animals, or those that live the longest lives. According to the United States Environmental Protection Agency, shark, swordfish, king mackerel and tileflish contain the highest amounts of mercury.
Recommendation
It is recommended that you limit yourself to a weekly maximum of 12 oz. of fish and shellfish that are low in mercury, such as shrimp, canned light tuna, salmon, pollock and catfish, or up to 6 oz. of albacore tuna or any kind of fish that you catch yourself. These levels are intended to ensure that the amount of methyl mercury in your body does not change. Exceeding this level one week will not change the amount of methyl mercury, as long as you are averaging these recommendations over a long duration.
Warning
Women who may become pregnant, women who are pregnant, nursing mothers and young children are the most vulnerable to mercury poisoning. This is due to the fact that exposure can affect the development of cognitive thinking, memory, attention, language and fine motor and spatial skills. In addition, poisoning can also cause impairment of periphery vision, disturbances in sensations, lack of coordinated movement, impairment of speech, hearing and walking and muscle weakness.
Considerations
If you worry about mercury in fish, it's possible to take omega-3 as a supplement without the possibility of incurring the negative effects of mercury poisoning. An article in the New York Times says that omega-3 supplements use fish lower on the food chain, such as cod and sardines, which contain negligible amounts of mercury. Even then, many companies distill their oil to remove contaminants. Studies by Consumer Lab and Harvard Medical School found little or no mercury in fish oil supplements.
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