The Science Behind Mercury in Fish
Mercury is a naturally occurring element that, when converted to methylmercury, becomes toxic and can accumulate in the food chain. This process, known as biomagnification, means that larger, longer-lived predatory fish tend to have the highest concentrations of mercury because they consume many smaller, mercury-containing fish throughout their lives. Cooking does not reduce the mercury content of fish.
The most commonly cited examples of high-mercury fish for sushi include certain species of tuna, king mackerel, and swordfish. Conversely, smaller fish and shellfish generally have much lower mercury levels, making them safer and more sustainable choices for regular consumption.
Safe Sushi: What sushi is not high in mercury?
For those who enjoy sushi, there are many delicious and nutritious low-mercury options to choose from. Opting for these choices can help reduce your overall exposure to mercury while still enjoying the health benefits of seafood, such as omega-3 fatty acids.
Low-Mercury Fish and Shellfish Options
- Salmon (Sake): A cornerstone of many sushi menus, salmon is known for its low mercury content, particularly farmed Atlantic salmon. It is also rich in heart-healthy omega-3s.
- Eel (Unagi/Anago): Conger eel (Anago) and freshwater eel (Unagi) are both relatively low in mercury compared to larger predators. They are also typically served cooked, which can reduce other potential risks.
- Shrimp (Ebi): Both cooked and raw shrimp are excellent low-mercury choices.
- Scallops (Hotategai): Shellfish like scallops consistently have very low mercury levels.
- Crab (Kani): Natural or imitation crab meat (kanikama), which is often made from lower-mercury pollock, is a safe option.
- Squid (Ika) and Octopus (Tako): These smaller marine animals are low in mercury and make great sushi choices.
- Salmon Roe (Ikura) and Flying Fish Roe (Tobiko): Fish eggs generally contain minimal mercury.
High-Mercury Fish to Limit
To minimize mercury exposure, it is wise to moderate or avoid the following fish, which are often featured in sushi and sashimi:
- Tuna: Large species like Bigeye (often sold as ahi), Bluefin, and Albacore (often called shiro or white tuna) are high in mercury. Lighter, smaller tuna like skipjack or yellowfin have lower levels, but consumption should still be limited.
- Mackerel (Saba): While some mackerel is lower in mercury, the larger, predatory species like King mackerel should be limited.
- Yellowtail (Hamachi): The American Pregnancy Association advises caution with yellowtail. The NRDC also recommends holding back on yellowtail to reduce mercury exposure.
Comparison of Sushi Fish by Mercury Content
| Fish Category | Common Sushi Name | Mercury Level | Serving Recommendation | Reason for Mercury Level |
|---|---|---|---|---|
| Low Mercury | Salmon (Sake) | Low | Up to 2-3 servings/week | Smaller fish, often farmed |
| Low Mercury | Eel (Unagi/Anago) | Low | Up to 2-3 servings/week | Not a top predator |
| Low Mercury | Shrimp (Ebi) | Very Low | Up to 2-3 servings/week | Small, filter feeder |
| Low Mercury | Scallops (Hotategai) | Very Low | Up to 2-3 servings/week | Small, filter feeder |
| High Mercury | Tuna (Bigeye/Ahi) | High | Limit heavily | Large, long-lived predator |
| High Mercury | Yellowtail (Hamachi) | High | Limit | Large, predatory fish |
Specific Considerations for Vulnerable Populations
For women who are pregnant or nursing, as well as for young children, mercury exposure is a greater concern due to its potential impact on neurological development. Health organizations like the EPA and FDA provide specific advisories for these groups, recommending they avoid all high-mercury fish.
For those sensitive to mercury, focusing on lower-mercury options is even more important. Vegetarian sushi rolls are an excellent alternative, offering delicious variety without any mercury concerns. Cooked seafood rolls, such as cooked eel or shrimp tempura, are also safe options.
Practical Tips for Choosing Low-Mercury Sushi
Beyond simply knowing which fish are lower in mercury, there are practical steps you can take at the sushi bar:
- Embrace Variety: Don't rely solely on one type of fish. Diversifying your order with a mix of low-mercury fish and vegetable-based rolls can help balance any potential mercury intake.
- Ask About the Fish: Don't hesitate to ask your server or sushi chef about the specific type of fish being used. For example, some restaurants might use lower-mercury skipjack tuna instead of high-mercury bigeye.
- Consider Farmed vs. Wild: Some studies suggest that farmed salmon may have lower mercury levels than their wild counterparts because their diet is more controlled. In contrast, large, wild-caught predatory fish are more likely to contain high levels of accumulated mercury.
- Go Vegetarian: Rolls featuring ingredients like avocado, cucumber, sweet potato, or egg (tamago) are delicious, nutritious, and completely mercury-free.
- Consult a Guide: For more detailed information on specific fish species, a resource like the NRDC Mercury Guide can be very helpful.
Conclusion: Making Smarter Sushi Choices
By understanding the fundamentals of mercury accumulation in seafood, it's easy to confidently answer the question of what sushi is not high in mercury? Your best options are smaller, shorter-lived fish and shellfish such as salmon, eel, shrimp, and scallops. By moderating your intake of large, predatory fish like bigeye tuna and embracing delicious alternatives, you can enjoy sushi as part of a healthy, balanced diet with minimal risk. Knowledge is the key to both delicious and healthy dining.
