Canned tuna is a popular and convenient source of protein, healthy fats, and essential vitamins, but the presence of mercury can be a concern for consumers. Mercury is a naturally occurring heavy metal that becomes more concentrated in larger, predatory fish like some species of tuna through a process called biomagnification. High mercury exposure can pose health risks, particularly for pregnant individuals, young children, and those with a compromised immune system.
The Difference in Mercury Levels by Tuna Species
The species of tuna is the most significant factor determining its mercury content. The general rule is: the smaller and younger the fish, the lower the mercury concentration. The two most common types of tuna found in cans are skipjack and albacore.
- Skipjack Tuna (Canned Light Tuna): This is the species typically labeled as 'canned light tuna' or 'chunk light'. As a smaller, faster-growing fish, skipjack has significantly lower levels of mercury than albacore. The FDA and EPA categorize it as a "best choice" for consumption.
- Albacore Tuna (Canned White Tuna): Labeled as 'canned white tuna' or 'albacore,' this species is larger and lives longer than skipjack, which allows it to accumulate higher levels of mercury. The FDA classifies albacore as a "good choice," but recommends limiting consumption.
- Yellowfin and Bigeye Tuna: These species are often sold as fresh steaks or used for sushi, but can sometimes be included in canned products. Yellowfin and, especially, bigeye tuna are larger and have higher mercury content, with bigeye containing the most.
Comparing Canned Tuna Types
| Feature | Canned Light Tuna (Skipjack) | Canned White Tuna (Albacore) |
|---|---|---|
| Mercury Level | Low | Higher |
| Flavor | Stronger, more "fishy" flavor | Milder, lighter flavor |
| Texture | Softer, chunkier texture | Firmer, more steak-like |
| Best For... | Casseroles, tuna salad with mayonnaise | Salads, dishes where a firmer texture is desired |
| Price | Generally more affordable | Often more expensive |
Finding the Safest Canned Tuna
Beyond just choosing the right species, several other factors can help you select the least toxic canned tuna.
Look for Individual Fish Testing
Some brands, such as Safe Catch, use proprietary technology to test each individual tuna for mercury before it's canned. The company claims its Elite Wild Tuna meets stricter mercury limits than competitors. While Consumer Reports found other light tunas were also low in mercury, this individual testing offers an added layer of assurance for some consumers.
Prioritize Fishing Methods
Certain fishing methods are more sustainable and can impact the size of the fish caught. Look for labels that say 'pole-and-line caught' or 'troll-caught'. These methods typically catch smaller, younger fish with lower mercury levels and have less bycatch of other marine species. Avoid products that do not specify fishing methods, as these might use large nets that catch older, larger fish.
Check Certifications and Labels
Certifications like the Marine Stewardship Council (MSC) can indicate that a product comes from a sustainably managed fishery with rigorous traceability standards. However, certifications are not a direct guarantee of low mercury, so combining this with checking the species is the best approach. Also, consider brands that specifically mention lower mercury levels on their packaging, like Safe Catch.
Consumption Recommendations and Alternatives
The FDA and EPA provide guidance to help individuals, especially sensitive populations, manage their mercury intake from fish.
- For Adults: The FDA recommends 2–3 servings (8 to 12 ounces) of canned light tuna per week. For albacore, it's recommended to limit consumption to one serving (4 ounces) per week.
- For Pregnant/Breastfeeding Individuals and Young Children: The developing nervous system is particularly sensitive to mercury. The FDA recommends 2–3 servings of canned light tuna per week, but some experts advise avoiding tuna altogether and choosing other low-mercury options.
Low-Mercury Seafood Alternatives
For those who want to minimize their mercury intake, excellent low-mercury fish and seafood alternatives include:
- Salmon (canned or fresh)
- Sardines
- Oysters
- Shrimp
- Tilapia
- Scallops
- Anchovies
Conclusion: Making a Smarter Choice
Choosing the least toxic canned tuna involves being a savvy consumer. By prioritizing canned light tuna made from skipjack, you can ensure significantly lower mercury exposure compared to albacore. Further reinforcing this choice by selecting brands that use individual fish testing or sustainable fishing methods (like pole-and-line) can offer even greater peace of mind. For those needing to be extra cautious, like pregnant women, opting for other low-mercury seafood like salmon and sardines is the safest bet. Canned tuna can remain a nutritious part of a balanced diet when you choose wisely and adhere to consumption guidelines.
A Note on Draining Canned Tuna
Mercury binds to the protein in a fish's muscles and is not water-soluble. Therefore, draining the fluid from the can, whether oil or water, has no significant impact on the mercury content. However, draining water-packed tuna can slightly reduce sodium, while draining oil-packed tuna will reduce calories and fat.
How Canned Tuna is Made
Knowing how canned tuna is processed can help understand its nutritional profile. After being caught, tuna is typically frozen and shipped to canning facilities. The fish is cooked, and the meat is separated, packed into cans, and then sealed and sterilized. The processing method for brands like Safe Catch differs, as they pack raw, sashimi-grade tuna into the can and then slow-cook it in its own natural juices to retain omega-3 oils.
Nutritional Benefits of Canned Tuna
Despite mercury concerns, canned tuna provides important health benefits. It is an excellent source of protein, helping with muscle growth and satiety. Tuna is also rich in omega-3 fatty acids (EPA and DHA), which support heart, brain, and immune health. Additionally, it contains B vitamins, vitamin D, selenium, and iron. Canned tuna can be a cost-effective way to include these nutrients in your diet.
