Understanding Mercury in Tuna
Mercury is a naturally occurring element, but industrial activity has increased its presence in our oceans. In marine environments, microorganisms convert it into methylmercury, a highly toxic organic compound that accumulates in the food chain. Larger, predatory fish like tuna, which live longer and eat other mercury-containing fish, tend to have the highest concentrations. This process is known as biomagnification.
While the FDA regulates mercury levels and has set an "action limit" of 1 part per million (ppm) for commercial fish, concentrations vary widely by species. Consumers looking to minimize mercury exposure should understand these differences, as well as the practices certain brands use to reduce risk.
The Safest Canned Tuna Choices
If you're seeking canned tuna with the lowest mercury levels, the species of tuna is the most critical factor. Smaller, shorter-lived tuna species like skipjack generally contain far less mercury than larger species like albacore or bigeye.
- Skipjack Tuna: Often labeled as "chunk light" tuna, skipjack is a smaller, fast-growing species that typically has the lowest mercury levels. It's the most common type of tuna used in canned light varieties.
- Species-Tested Brands: Some companies take extra steps to ensure low mercury content by individually testing each fish before canning. Brands like Safe Catch and Wild Planet use proprietary technology to test every single tuna, guaranteeing their products meet stricter mercury limits than the FDA's standard.
- Pole-and-Line Caught: The method of fishing can also be a good indicator. Pole-and-line fishing tends to catch smaller, younger fish, which generally have less time to accumulate mercury. This is often noted on the product label.
Types of Canned Tuna and Their Mercury Levels
While some brands offer added assurances, the species remains the best indicator of a product's average mercury content. Here is a comparison of common canned tuna types:
| Tuna Type | Typical Labeling | Mercury Level | Best for... |
|---|---|---|---|
| Skipjack Tuna | Chunk Light, Light Tuna | Lowest average levels | Frequent consumption, budget-friendly |
| Yellowfin Tuna | Ahi Tuna | Moderate to higher levels | Occasional eating due to higher mercury |
| Albacore Tuna | White Tuna | High average levels | Less frequent consumption; limit intake |
| Bigeye Tuna | Ahi Tuna | Highest average levels | Best to avoid; very high mercury |
How to Reduce Your Overall Mercury Intake
Beyond choosing the right tuna, consumers can adopt several practices to further minimize their mercury exposure from seafood. These strategies are especially important for sensitive populations like pregnant women, nursing mothers, and young children, who are more susceptible to mercury's neurotoxic effects.
Diversify Your Seafood Choices
Don't rely solely on tuna for your fish intake. The FDA recommends eating a variety of fish and shellfish as part of a healthy diet, and many excellent options have naturally low mercury levels.
- Salmon: A great source of protein and omega-3 fatty acids, with very low mercury levels.
- Sardines: Another small, low-mercury, and omega-3 rich choice.
- Mackerel: Atlantic mackerel is low in mercury, unlike larger species like king mackerel.
- Shrimp, clams, and scallops: These are all excellent low-mercury shellfish options.
Follow Consumption Guidelines
The FDA and EPA issue joint guidelines on fish consumption based on mercury content. For most adults, moderate consumption of canned light tuna is generally safe. For more sensitive groups, the recommendations are more restrictive. Some experts even advise pregnant women to opt for smaller fish altogether to be safe. Always consult the latest guidelines from reputable health organizations.
Look for "Tested" or "Low Mercury" Claims
While you should still consider the species, some brands explicitly advertise their testing process. For example, Safe Catch's Wild Elite tuna is tested to a strict mercury limit that is 25 times stricter than the FDA's standard. This provides an additional layer of confidence for those particularly concerned about mercury.
Drain the Tuna Properly (Minor Effect)
Some studies suggest that draining the liquid from canned tuna may have a minor, though not significant, effect on reducing mercury levels, as most mercury is bound to the fish tissue. However, the most impactful change comes from choosing a low-mercury species.
Conclusion
While no commercially available canned tuna is completely mercury-free, you can make informed choices to significantly reduce your exposure. The key is to opt for smaller, shorter-lived species like skipjack, typically labeled as "chunk light" tuna, over larger fish like albacore. Furthermore, choosing brands like Safe Catch that individually test each fish offers the highest level of assurance. By diversifying your protein sources and following official consumption guidelines, you can enjoy the nutritional benefits of seafood while effectively managing your mercury intake.
The Takeaway
- No Canned Tuna is Mercury-Free: All fish contain trace amounts, but levels vary significantly by species.
- Choose Skipjack: Opt for smaller, shorter-lived skipjack tuna (labeled as "chunk light") for the lowest mercury content.
- Consider Albacore with Caution: Albacore, or "white" tuna, has higher mercury levels and should be eaten less frequently.
- Look for Tested Brands: Some brands, like Safe Catch, test every fish for mercury, offering the lowest certified levels.
- Diversify Your Diet: Supplement tuna with other low-mercury seafood like salmon and sardines.
- Follow Guidelines: Heed FDA and EPA consumption guidelines, especially for sensitive groups like pregnant women and young children.
- Limit Overall Intake: Consume tuna in moderation as part of a varied diet to minimize mercury accumulation over time.
