Many types of fish are an important part of a well-rounded diet. Tuna, for instance, is low in saturated fat, high in protein and rich in heart-healthy omega-3 fatty acids. However, tuna and other fish can contain methylmercury, a toxic substance that can cause long-term health problems if you consume too much of it, according to the Alabama Cooperative Extension System.
The Problem
Factories and other industrial entities release mercury into the environment and into oceans and streams, where it turns into methylmercury with the help of bacteria. Fish absorb methylmercury, but the largest fish tend to contain the highest levels of mercury because they are heavier, they have larger surface areas for absorption and they eat smaller fish that also contain mercury, according to Health Services at Columbia University. The U.S. Environmental Protection Agency most strongly recommends against eating large predator fish such as shark and swordfish, but also recommends limiting your intake of other large fish such as tuna. You should use caution when eating both albacore and light tuna, but light tuna is smaller and tends to contain much less mercury than albacore does.
Health Risks
If you develop mercury poisoning as an adult, you may develop symptoms such as tremors, numbness in your toes and fingers and loss of vision and memory. However, fetuses, infants and young children are mostly the object for mercury warnings because mercury exposure during development can lead to physical disabilities and mental retardation. Talk to your OB/GYN as soon as possible if you are pregnant and regularly eat tuna or other large fish and consult your child's pediatrician if you regularly feed your child any of these fish. Also get in touch with your doctor as soon as possible if you believe you're experiencing any symptoms of mercury poisoning.
How Much
The U.S. Environmental Protection Agency says that young children and women who can become pregnant can eat as much as 12 oz. of light tuna or other "low mercury" seafood a week or up to 6 oz. of albacore tuna a week. However, "Consumer Reports" makes more specific -- and stringent -- recommendations. It suggests that children under 45 lbs. eat 4 oz. or less of light tuna or 1.5 oz. or less of albacore tuna per week and recommends that children over 45 lbs. eat no more than 4 oz. to 12.5 oz. of light tuna or 1.5 oz. to 4 oz. of white tuna per week. It also suggests that women who can become pregnant eat no more than 12.5 oz. of light tuna or 4 oz. of albacore per week and that pregnant women completely avoid canned tuna. According to its recommendations, men and older women can eat no more than about 14.5 oz. of light tuna or 5 oz. of albacore tuna each week.
Tips for Fresh Caught Tuna
If you fish for tuna or eat tuna that any family members or friends have caught, check your local advisories for the safety of fish in your local bodies of water, recommends the U.S. Environmental Protection Agency. You can usually find advisories from your local health department. If you can't find any information, avoid eating more than about 6 oz. of locally caught fish, but avoid consuming any other type of fish in the same week.
References
- "Consumer Reports" magazine; How Much Tuna is Safe?; 2011
- Health Services at Columbia University: Mercury Poisoning: Something Fishy About Too Much Tuna?; 2007
- Alabama Cooperative Extension System: How Much Fish is Too Much?; 2003
- National Resources Defense Council: Eating Tuna Safely: Mercury Contamination in Fish
- What You Need to Know About Mercury in Fish and Shellfish?: 2004 EPA and FDA Advice
- Environmental Protection Agency: Mercury
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