Understanding Mercury in Fish
Mercury is a naturally occurring element that enters our waterways and accumulates in fish as methylmercury. All fish contain some level of mercury, but the amount varies significantly by species. This is primarily due to bioaccumulation, a process where mercury concentrates in larger, longer-lived fish higher up the food chain. Predatory fish like bigeye tuna, swordfish, and shark, therefore, carry the highest risk. Cooking methods do not reduce the mercury content, as it binds to the fish's muscle tissue. For consumers, especially sensitive groups like pregnant women, young children, and nursing mothers, knowing which species are low in mercury is essential for safely enjoying the nutritional benefits of seafood.
The Low-Mercury Champions: Skipjack and Canned Light Tuna
Of all the tuna species, skipjack is consistently the one with the lowest mercury levels. This is because skipjack tuna are smaller and have a shorter lifespan than other tuna species. Canned light tuna is almost always made from skipjack, which is why it is the safest, most recommended option for regular consumption. Canned light tuna has been identified by the FDA and EPA as a "Best Choice" category, suggesting it can be consumed two to three times per week by most adults. Beyond its low mercury content, skipjack tuna is a nutrient powerhouse, offering a rich source of protein, vitamin B12, selenium, and heart-healthy omega-3 fatty acids. Its firm texture and mild flavor make it a versatile and affordable pantry staple.
Higher-Mercury Tuna Varieties to Limit
To minimize mercury exposure, it is advisable to limit consumption of larger tuna species.
Albacore (White) Tuna
Albacore tuna, often sold as "white" tuna, is a larger and longer-living species than skipjack. Consequently, it accumulates more mercury. For adults, the FDA considers albacore a "Good Choice" but recommends limiting intake to just one 4-ounce serving per week. For children, the advice is to consume even less, or to avoid it altogether. Canned albacore has approximately three times more mercury on average than canned light tuna.
Yellowfin and Bigeye Tuna
Yellowfin (sometimes called ahi) and bigeye tuna are often sold as fresh or frozen steaks and are popular in sushi. These species have higher mercury concentrations due to their size and position higher up the food chain. The FDA places yellowfin in the "Good Choice" category, recommending limited intake for sensitive groups. Bigeye tuna, the largest and longest-living of the commonly consumed tuna, carries the highest mercury risk and is listed in the "Choices to Avoid" category for women who are pregnant or breastfeeding and young children.
Comparison of Mercury Levels in Tuna
To make informed choices, compare the average mercury levels of different tuna types.
| Tuna Species | Mercury Level (ppm) | Serving Recommendation for Adults (FDA) |
|---|---|---|
| Canned Light (Skipjack) | 0.126 | 2–3 servings per week |
| Fresh/Frozen Skipjack | 0.144 | 2–3 servings per week |
| Canned Albacore | 0.350 | 1 serving per week |
| Fresh/Frozen Yellowfin | 0.354 | 1 serving per week (Good Choice) |
| Fresh/Frozen Bigeye | 0.689 | Limited to Avoid (Choices to Avoid for sensitive groups) |
Beyond Tuna: Other Low-Mercury Seafood Options
For a balanced diet, consider diversifying your seafood consumption with other low-mercury options, many of which are rich in omega-3s.
- Salmon: Both wild-caught and farmed salmon generally contain low mercury levels and are excellent sources of omega-3 fatty acids.
- Sardines: A fantastic and sustainable low-mercury choice, sardines are packed with nutrients.
- Shrimp: Among the most widely consumed seafood, shrimp is very low in mercury.
- Tilapia: A popular and very low-mercury fish.
- Pollock: This is a great choice for fish sticks and fillets due to its low mercury content.
Conclusion
While tuna can be a healthy part of a balanced diet, it is crucial to manage mercury exposure by choosing the right species. The answer to 'what kind of tuna is lowest in mercury' is unequivocally skipjack, which is typically sold as canned light tuna. By opting for this smaller, shorter-lived variety and limiting intake of larger species like albacore and bigeye, consumers can enjoy the health benefits of fish with minimal risk. Always follow government guidelines and consider diversifying your seafood with other low-mercury alternatives to ensure safety for yourself and your family. For official recommendations, refer to the FDA-EPA Advice on Eating Fish.
