Understanding Mercury in Canned Tuna
Mercury is a naturally occurring element that enters our oceans through both natural events, like volcanic activity, and human industrial pollution. Once in the water, bacteria convert it to methylmercury, a highly toxic form that accumulates in the food chain. Fish absorb methylmercury from the water and through the smaller fish they eat. This process, known as bioaccumulation, means larger, older predatory fish higher on the food chain tend to have the highest concentrations of mercury. Since tuna species vary significantly in size and lifespan, their mercury levels also differ considerably, which is the primary factor determining the safest canned tuna choice.
Comparing Canned Tuna Species: Light vs. Albacore
When shopping for canned tuna, you will primarily encounter two types: canned light tuna and canned white (albacore) tuna. The difference between these two goes beyond flavor and texture and is critical for understanding mercury levels.
- Canned Light Tuna: This product is typically made from skipjack or, less commonly, yellowfin tuna. Skipjack are smaller, younger, and faster-growing fish than albacore, meaning they have less time to accumulate mercury. As a result, canned light tuna has the lowest average mercury levels, and the FDA and EPA classify it as a "Best Choice". This makes it a great option for more frequent consumption within recommended guidelines.
- Canned White (Albacore) Tuna: Albacore tuna is a larger, longer-living species, which leads to a higher accumulation of mercury. The FDA places albacore tuna in its "Good Choices" category, recommending a lower weekly intake than for light tuna. Due to the higher mercury content, albacore tuna is not typically recommended for children.
How Much Canned Tuna is Safe to Eat?
For most healthy adults, consuming canned tuna as part of a balanced diet is safe within recommended limits. However, the amount and frequency depend on the type of tuna and individual health considerations, especially for vulnerable populations like pregnant women and children. The FDA provides clear guidelines to help consumers make informed choices.
FDA/EPA Guidelines for Tuna Consumption
- For adults: 2 to 3 servings per week (about 8–12 ounces total) of canned light tuna are recommended. For albacore tuna, the recommendation is limited to 1 serving per week (about 4 ounces).
- For pregnant or breastfeeding women: The same guidelines apply, making canned light tuna a much safer option for moderate consumption. However, some groups, like Consumer Reports, advise pregnant women to avoid all tuna due to the potential for unpredictable mercury spikes in individual cans.
- For children: Serving recommendations for children vary by age and should focus on canned light tuna. The EPA and FDA rank light tuna among the "best choices" for children, recommending 2-3 servings per week.
Factors Affecting Canned Tuna's Safety
Beyond the species, several other factors can influence the safety and quality of your canned tuna.
Sourcing and Catch Method
How and where the tuna is caught plays a significant role in both sustainability and mercury content. Sustainable methods often target younger, smaller fish, which inherently have lower mercury levels.
- Pole-and-line caught: This traditional method uses a single hook and line, minimizing bycatch and often catching smaller, lower-mercury fish.
- Troll-caught: Similar to pole-and-line, this method involves fishing lines being towed slowly behind a boat, which also helps catch younger fish.
- Geographic location: Tuna from specific areas may have different mercury levels. For example, some regional albacore, like from the Pacific Northwest, have been found to have lower mercury than imported varieties.
Brands and Mercury Testing
Some brands have taken extra steps to ensure their products are as low in mercury as possible. For instance, Safe Catch is known for testing every single tuna they catch for its mercury content before it is canned. Other brands, like Wild Planet, focus on sourcing smaller, younger tuna to minimize mercury accumulation. While many standard brands meet safety regulations, consumers concerned about minimizing mercury exposure can opt for brands that offer individual-can testing or specialized sourcing.
Packing Liquid: Water vs. Oil
The liquid the tuna is packed in—either water or oil—affects the calorie and fat content but has no impact on the mercury levels.
- Tuna in water: A good choice for those watching their calorie and fat intake, as it provides a lean source of protein.
- Tuna in oil: Higher in calories and fat, which can be beneficial for those needing more dietary fats, including heart-healthy omega-3s, but also higher in overall caloric density.
Canned Tuna Comparison Table
| Feature | Canned Light Tuna (Skipjack) | Canned White Tuna (Albacore) |
|---|---|---|
| Mercury Levels | Lower average levels | Higher average levels |
| FDA/EPA Choice | "Best Choice" | "Good Choice" |
| Recommended Servings (Adult) | 2–3 servings (8–12 oz) per week | 1 serving (4 oz) per week |
| Species Type | Skipjack (mainly), Yellowfin | Albacore |
| Size/Age of Fish | Smaller, younger fish | Larger, older fish |
| Flavor Profile | Stronger, more "fishy" flavor | Milder, more delicate flavor |
| Color and Texture | Pinkish color, softer texture | Pale, whitish color, firmer texture |
Conclusion: Making the Safest Choice
Choosing the safest canned tuna involves being mindful of the species, its sourcing, and your individual dietary needs. For the lowest mercury exposure, canned light tuna, especially from brands that prioritize testing or selective sourcing, is your best bet. While all canned tuna available in the US is regulated and generally considered safe for consumption within recommended limits, understanding the differences between species empowers you to make a healthier choice. By opting for smaller, younger fish and moderating your intake, particularly of higher-mercury albacore, you can enjoy the nutritional benefits of this convenient protein source while minimizing potential risks. As with any food, variety is key to a balanced and healthy diet, so be sure to include other low-mercury fish like salmon and sardines.
Top Picks for Low-Mercury Canned Tuna
- Safe Catch: The only brand that individually tests every fish for mercury, with products like their Wild Elite and Albacore options.
- Wild Planet: Focuses on sustainably catching smaller, younger fish to ensure lower mercury content, offering both skipjack and albacore options.
- American Tuna: This brand uses pole-and-line fishing and sources from American fishing communities, prioritizing sustainability and lower-mercury catches.
- Oregon's Choice Gourmet: Sourcing smaller albacore from the West Coast, this brand offers a lower-mercury albacore option.
- Bumble Bee and StarKist Chunk Light: These widely available and affordable options are typically made from skipjack tuna and fall into the "Best Choice" low-mercury category.
- 365 Whole Foods Market: Their Albacore Wild Tuna is pole-and-line caught and third-party certified for sustainability, making it a good choice for those concerned with ethical sourcing.
