Understanding Mercury in Tuna
To understand why you can't simply remove mercury from canned tuna, you first have to understand the form it takes. The primary mercury compound found in fish is methylmercury, a potent neurotoxin. This organic compound is created when bacteria in aquatic environments convert elemental mercury into methylmercury, which is then absorbed by small organisms and bioaccumulates up the food chain. Because tuna are predatory fish higher up the food chain, they accumulate more methylmercury in their muscle tissue over their lifespan compared to smaller fish like sardines or mackerel. Once the mercury is bound to the fish's tissue proteins, it becomes an intrinsic part of the food and cannot be washed or drained away. Studies have confirmed that draining the liquid (whether oil or water) from canned tuna does not reduce the mercury content.
Recently, researchers have been investigating industrial methods to remove mercury from fish during the processing phase, such as using an amino acid solution (cysteine) in the packaging liquid. Early results showed a reduction of up to 35% in canned minced tuna. However, this technology is not yet widely implemented and remains an industrial-scale solution, not a method for at-home preparation.
Making Smarter Choices to Reduce Exposure
Since you cannot remove the mercury, the most effective strategy for reducing your intake is to make informed decisions before you buy and eat canned tuna. This involves choosing the right type of tuna and moderating your consumption.
Choose Smaller, Lower-Mercury Species
Not all canned tuna is created equal. The mercury content varies significantly depending on the species of tuna used. Smaller and younger tuna species generally contain less mercury than larger, older ones.
- Canned Light Tuna: This is typically made from skipjack tuna, a smaller species with a shorter lifespan. The FDA considers canned light tuna a "best choice" due to its lower mercury levels.
- Albacore ("White") Tuna: Albacore is a larger species of tuna, and consequently, canned white tuna contains nearly three times the mercury of canned light tuna. The FDA categorizes it as a "good choice" with stricter consumption guidelines.
Diversify Your Seafood Choices
One of the best ways to limit your mercury exposure is to not rely on a single type of fish. By adding a variety of seafood to your diet, you can still reap the nutritional benefits of fish, such as omega-3 fatty acids, while minimizing the risk of mercury accumulation.
Low-Mercury Seafood Alternatives:
- Canned salmon (pink or sockeye)
- Sardines
- Shrimp
- Cod
- Tilapia
- Mackerel (Atlantic or Chub, not King Mackerel)
Follow Recommended Consumption Guidelines
Health organizations provide clear recommendations on how much tuna can be safely consumed per week. These guidelines are especially important for vulnerable populations, including pregnant women, young children, and women of childbearing age, who are more susceptible to the neurotoxic effects of mercury.
- For Canned Light Tuna: The FDA recommends adults can safely eat two to three servings (8 to 12 ounces) per week.
- For Canned Albacore Tuna: The FDA recommends limiting consumption to one serving (4 ounces) per week for adults.
Comparison of Canned Tuna Varieties
| Feature | Canned Light Tuna (Skipjack) | Canned Albacore Tuna (White) |
|---|---|---|
| Mercury Level (Average) | Lower (approx. 0.126 ppm) | Higher (approx. 0.350 ppm) |
| FDA Recommendation (Adults) | 2-3 servings (8-12 oz) per week | 1 serving (4 oz) per week |
| Source Species | Skipjack (Katsuwonus pelamis) | Albacore (Thunnus alalunga) |
| Average Size of Fish | Smaller (approx. 6-12 pounds) | Larger (approx. 25-45 pounds) |
| Appearance | Pinkish color, softer texture | Whiter color, firmer texture |
The Role of Selenium
While not a method for removing mercury, some fish, including tuna, also contain selenium. Selenium has been shown to counteract the toxicity of methylmercury by binding to it and creating a less harmful compound. This means that the ratio of selenium to mercury in a fish can affect its overall toxicity. However, relying on this biological interaction is not a substitute for choosing lower-mercury options and moderating intake, especially for vulnerable individuals.
Conclusion
In summary, there is no effective home remedy to get rid of mercury in canned tuna. The mercury, primarily in the form of methylmercury, is an integral part of the fish's muscle tissue and cannot be drained or cooked out. Instead of attempting impossible removal methods, consumers should focus on practical, preventative strategies. These include choosing lower-mercury tuna species like skipjack (canned light), diversifying seafood choices with options like salmon and sardines, and strictly adhering to consumption limits recommended by health authorities like the FDA. For at-risk groups, such as pregnant women and young children, minimizing or avoiding higher-mercury options like albacore is particularly important for safeguarding health and development.
For more detailed information on mercury levels in various fish and seafood, consult the FDA's mercury reference data.
