Understanding Mercury in Tuna
Mercury is a naturally occurring heavy metal that can be harmful to human health, especially to the developing brain and nervous systems of fetuses and young children. In the aquatic environment, mercury is converted by bacteria into a more toxic form called methylmercury, which is then absorbed by small fish. As larger fish consume smaller ones, the methylmercury accumulates in their tissue, a process known as bioaccumulation. This is why larger, older predatory fish tend to have higher concentrations of mercury than smaller fish.
For tuna, this biological reality means that the species you choose is one of the most critical factors in determining mercury levels. Larger species, such as albacore, bigeye, and yellowfin, contain higher mercury levels than smaller, fast-growing skipjack tuna, which is most commonly used for canned 'light' tuna. The average mercury concentration for canned light tuna is significantly lower than for canned albacore.
Brand Testing and Mercury Levels
While species is the primary differentiator, testing by independent organizations and manufacturers shows that mercury levels can still vary from can to can, even within the same brand and type. Some brands have taken unique approaches to minimize mercury, while others rely on standard processing methods. A key consideration is whether a brand tests its fish individually or relies on average data.
Safe Catch: The Individual Fish Testing Approach
Safe Catch is the only brand that claims to test every single fish for mercury before canning. According to the company, it tests each fish to a strict mercury limit that is 2.5 to 10 times lower than the FDA's action limit, depending on the product line. This method allows them to guarantee that their tuna is the lowest mercury option, and their Elite Wild Tuna is the official tuna of the American Pregnancy Association. However, Consumer Reports found in its testing that while Safe Catch had relatively low levels, many other brands' light tunas were comparable, and Safe Catch's albacore levels were close to other brands tested.
Wild Planet: The Sustainability First Approach
Wild Planet prioritizes sustainable fishing methods like pole-and-line catching, which often targets smaller, younger fish. However, a Consumer Reports test revealed that their skipjack tuna had higher mercury levels than other light tuna brands tested, putting it in the 'one serving per week' category for adults, similar to albacore. Wild Planet acknowledged that they chose a sustainability-focused approach rather than the lowest possible mercury level. Their albacore was also tested and found to have levels similar to their skipjack.
Conventional Brands: Bumble Bee, StarKist, and Chicken of the Sea
For those seeking affordable, low-mercury options, conventional canned light tuna from major brands is often the go-to choice. A Consumer Reports analysis found that Bumble Bee Chunk Light, Chicken of the Sea Chunk Light, and StarKist Chunk Light were among the safer choices for frequent consumption, with average mercury levels low enough to recommend three servings per week for non-pregnant adults. However, Consumer Reports also identified unpredictable spikes in mercury levels in some individual cans from these brands, highlighting the variability.
Canned Tuna Mercury Comparison Table
| Tuna Product | Primary Species | Average Mercury Level | Consumer Recommendation | Special Notes |
|---|---|---|---|---|
| Safe Catch Elite Wild Tuna | Skipjack | Very Low | Recommended for frequent consumption due to individual testing | Claims lowest mercury of any brand due to individual testing |
| Bumble Bee Chunk Light | Skipjack | Low | Can be eaten 2-3 times per week by most adults | One of the safer, more affordable chunk light options |
| Chicken of the Sea Chunk Light | Skipjack | Low | Can be eaten 2-3 times per week by most adults | A widely available, low-mercury light tuna |
| StarKist Chunk Light | Skipjack | Low | Can be eaten 2-3 times per week by most adults | Also available in low-sodium options |
| Wild Planet Skipjack | Skipjack | Varies, potentially higher than other light tunas | May warrant less frequent consumption based on testing | Focuses on sustainable fishing methods |
| Albacore (White) Tuna | Albacore | Moderate to High | Limit to 1 serving per week for most adults | Generally larger fish, higher mercury; check brand testing for specific values |
Choosing the Safest Tuna: A Guide for Consumers
Making informed choices about tuna consumption involves more than just picking a brand. You can minimize your mercury exposure by considering the following factors:
- Prioritize canned light tuna: Canned light tuna, which is primarily skipjack, contains significantly less mercury than canned albacore or other larger species. Make this your default choice for regular consumption.
- Evaluate testing claims: Brands like Safe Catch, which test every fish, offer a higher level of assurance regarding mercury content, though they often come with a higher price point.
- Mind your overall consumption: Even with low-mercury options, balancing your total fish intake is wise. The FDA recommends 2-3 servings of low-mercury fish per week for most adults.
- Consider low-mercury alternatives: There are many other nutritious seafood options with very low mercury levels. Incorporating other types of fish can help you meet omega-3 needs without relying solely on tuna. Examples include:
- Wild-caught salmon
- Sardines
- Anchovies
- Catfish
- Clams
- Look for sustainability labels: While not a direct indicator of mercury levels, sustainable fishing practices like pole-and-line catching often target smaller, younger fish, which typically have lower mercury counts.
Conclusion: Making Informed Choices
No brand of tuna is completely mercury-free, but by prioritizing canned light (skipjack) tuna and considering brands with stringent testing, you can significantly reduce your mercury exposure. For the most guaranteed low-mercury option, brands like Safe Catch provide an individualized testing approach, albeit at a higher cost. For more budget-friendly options, conventional brands of chunk light tuna offer a generally safe choice, though with some can-to-can variation. Ultimately, understanding species differences and diversifying your seafood intake with other low-mercury options like salmon and sardines are key to a balanced, safe diet.
For more information on fish consumption, you can refer to the FDA's guidance: https://www.fda.gov/food/metals/mercury-levels-commercial-fish-and-shellfish-2023
