Eating fish weekly is recommended as part of a healthy diet. Tuna and other fish are high in healthy omega-3 fatty acids and other nutrients, and low in the less healthy saturated fat. But you may be concerned about the amount of contaminants in fish, particularly mercury. The health benefits of tuna will likely outweigh the potential risks if you consume the right type in the correct amounts.
Health Benefits
Regular fish intake can potentially decrease your risk of heart disease and inflammation, and improve memory and neurological development. An October 2006 review in "The Journal of the American Medical Association" found that a modest intake of 250 500 mg omega-3 fatty acids daily decreased risk of death from coronary heart disease by 25 percent. A 3 oz serving of tuna, about the size of a deck of cards, can have between 228 and 733 mg of omega-3. The American Dietetic Association recommends 12 oz. of fish per week to reap the omega-3 benefits.
Mercury
Mercury comes from natural sources like volcanoes, and manmade sources like power plants and waste incineration. It gets into the atmosphere and is deposited in lakes and oceans where it is turned into methylmercury, a form that may be harmful to humans if ingested in large amounts. The larger the fish, the more time it has had to accumulate methylmercury. Methylmercury can interfere with neurological development in fetuses, infants and children. Methylmercury overdose in adults is less common, but can include lack of coordination, speech impairment and muscle weakness, according to the U.S. Environmental Protection Agency.
Mercury in Tuna
Mercury levels in tuna vary depending on the source and size. Canned, light tuna has a lower average mercury content of 0.128 ppm, according to the U.S. Food and Drug Administration. Other varieties of tuna are not listed in the lower or highest mercury level categories, but fall somewhere in the middle. The FDA places average mercury levels of tuna as follows: fresh/frozen skipjack tuna 0.144 ppm, canned albacore tuna 0.350 ppm, fresh/frozen yellowfin tuna 0.354 ppm, fresh/frozen albacore tuna 0.358 ppm, all fresh/frozen tuna 0.391 ppm, fresh/frozen unknown species of tuna 0.415 ppm, and fresh/frozen bigeye tuna 0.689. No species of tuna make the list of the highest levels of mercury, with averages from 0.730 to 1.450 ppm.
Considerations
Tuna is generally considered a good source of omega-3 fatty acids, and contains low to moderate levels of methylmercury. It's recommended that pregnant women consume 12 oz. low-mercury level fish per week, like canned light tuna, according to the EPA. Because albacore tuna is higher in mercury, pregnant women should only consume up to 6 oz per week. Consult your physician if you would like more information regarding your specific omega-3 needs and mercury risks.
References
- "The Journal of the American Medical Association"; Fish Intake, Contaminants, and Human Health; Dariush Mozaffarian, et al.; October 2006
- American Dietetic Association; Feed Your Brain. Go Fish!; Daisha Cassel
- EPA: Health Effects Mercury
- FDA; Mercury Levels in Commercial Fish and Shellfish; January 2006
- EPA; What You Need to Know About Mercury in Fish and Shellfish; 2004
