The concern over mercury in seafood has grown as awareness of its health risks has increased. Mercury is a neurotoxin that can cause harm in high concentrations, and it bioaccumulates in the food chain. This means that larger predatory fish, which eat smaller fish, accumulate higher levels of mercury in their tissues. For sushi lovers, this means that some of the most popular items on the menu can be a source of high mercury exposure, while many delicious and safe options exist.
Understanding Mercury Levels in Seafood
Mercury enters the aquatic environment from various sources, including pollution and natural phenomena like volcanoes. It then moves up the food chain. Species that are long-lived and high on the predatory chain, such as shark, swordfish, and certain types of tuna, will have the highest concentrations of mercury. Smaller, shorter-lived species, like most shellfish, have had less time and opportunity to accumulate high levels of the metal. It is important to note that mercury levels can also vary within a species depending on its size and age.
Low Mercury Sushi Options
Choosing sushi with low mercury is straightforward once you know which seafood to select. Look for options that feature shellfish or smaller fish species.
- Salmon (Sake): Both fresh and smoked salmon are excellent low-mercury choices. Farmed Atlantic salmon has particularly low levels of mercury.
- Shrimp (Ebi): Both cooked and sweet shrimp are low in mercury, offering a worry-free option.
- Eel (Unagi and Anago): Freshwater eel (unagi) and conger eel (anago) are delicious options with minimal mercury.
- Crab (Kani): Real crab meat and imitation crab (surimi), which is often made from pollock, are low in mercury. Be sure the imitation crab is pasteurized if you are in a high-risk group.
- Scallops (Hotategai): These shellfish are very low in mercury and are a delicate, flavorful sushi topping.
- Clams (Akagai, Hamaguri, etc.) and Other Shellfish: Abalone, cockles, and clams are all safe, low-mercury choices.
- Squid and Octopus (Ika and Tako): While both are large mollusks, they have relatively low mercury levels compared to large fish predators.
Comparing Mercury in Common Sushi Fish
To help make an informed decision, here is a comparison of mercury levels in some common sushi ingredients, based on available data from sources like the Environmental Working Group (EWG) and the American Pregnancy Association.
| Seafood Type | Mercury Level | Notes |
|---|---|---|
| Tuna (Bluefin, Bigeye) | High | Large, long-lived predators at the top of the food chain. |
| Swordfish | High | A large predator that bioaccumulates high levels of mercury. |
| King Mackerel | High | Another large predator to be limited or avoided. |
| Salmon (Sake) | Very Low | Much smaller and lower on the food chain. |
| Shrimp (Ebi) | Very Low | Shellfish and smaller species have minimal mercury. |
| Eel (Unagi) | Very Low | A smaller fish with low mercury concentration. |
| Scallops (Hotategai) | Very Low | Shellfish that filter-feed and do not accumulate much mercury. |
| Crab (Kani) | Very Low | Often imitation crab (surimi), which is also low in mercury. |
Sushi to Avoid or Eat in Moderation
While some high-mercury fish like tuna can be delicious, they should be consumed in moderation, especially by pregnant women, nursing mothers, and young children.
- Tuna (Maguro): Specifically, Bluefin and Bigeye tuna should be limited. Yellowfin (Ahi) is a moderate option but still contains higher levels than lighter fish. EWG notes that tuna in sushi can have three to ten times more mercury than other options.
- Swordfish (Kajiki): Due to its position as a large predator, this is one of the highest mercury fish.
- King Mackerel: Also a large predator with high mercury levels.
- Yellowtail (Hamachi): Adult yellowtail has moderate mercury levels and is best consumed infrequently.
Beyond the Fish: Non-Seafood Sushi
For those who want to completely avoid the risk of mercury, or simply prefer other flavors, many fantastic sushi rolls contain no fish at all.
- Avocado Rolls: Simple, creamy, and packed with healthy fats.
- Cucumber Rolls (Kappa Maki): Crisp, light, and refreshing.
- Tamago: A sweet, layered Japanese omelet that is fully cooked and mercury-free.
- Sweet Potato Tempura Rolls: Offer a delicious, cooked, and vegetarian alternative.
- Vegetable Rolls: Most restaurants offer a variety of rolls with vegetables like carrots, asparagus, and sprouts.
Conclusion: Making Informed Choices
Choosing low-mercury sushi is about understanding the fish's place in the food chain. By opting for smaller, shorter-lived species like salmon, shrimp, and eel, you can enjoy sushi's health benefits without the worry of excessive mercury exposure. For those concerned about any mercury, vegetarian or cooked options offer a safe and delicious alternative. Making informed decisions allows you to savor the flavors of sushi while prioritizing your health.
For more information on the mercury content of various seafood, consult a trusted guide, such as the Environmental Working Group's Consumer Guide to Seafood.
