Understanding Mercury in Fish
Mercury is a naturally occurring element that makes its way into the environment and oceans. In water, it is converted into methylmercury, a potent neurotoxin that accumulates in the bodies of fish and shellfish. The concentration of mercury in fish is directly related to its position in the food chain. Smaller, shorter-lived fish that feed on tiny organisms contain less mercury, while larger, predatory fish that eat smaller contaminated fish accumulate higher levels over their lifespan through a process called biomagnification.
For consumers, especially sensitive populations like pregnant women and young children, minimizing mercury intake is a primary concern when eating seafood. The canning process itself does not reduce the mercury content of the fish. Therefore, the type and size of fish originally canned are the most important factors in determining mercury levels in the final product.
The Lowest Mercury Canned Fish
For those seeking the safest options, canned sardines, anchovies, and salmon are consistently recommended by health authorities like the FDA. These fish are lower on the food chain, resulting in minimal mercury accumulation.
- Sardines: These small, oily fish are exceptionally low in mercury, with FDA data showing an average concentration of just 0.013 ppm. They are also a nutritional powerhouse, rich in omega-3 fatty acids, calcium, and vitamin D.
- Anchovies: Similar to sardines, anchovies are a tiny fish with very low mercury levels, around 0.02 ppm. They are also high in omega-3s but tend to be higher in sodium, so moderating intake or rinsing is advised.
- Canned Salmon: Canned salmon, particularly wild pink or sockeye, is a superb low-mercury choice. The salmon used for canning are often smaller and younger than their fresh or frozen counterparts, contributing to their low mercury profile. FDA data confirms canned salmon has significantly lower mercury than canned tuna.
- Canned Light Tuna (Skipjack): Among tuna varieties, canned light tuna, typically made from smaller skipjack tuna, is the lowest in mercury. While not as low as sardines or salmon, it's a popular and widely available low-mercury option. The FDA lists it as a "Best Choice," suitable for 2-3 servings per week for the general population.
Canned Fish Comparison
To help visualize the differences, here is a comparison table of common canned fish and their mercury levels, as reported by the FDA.
| Fish Type | Typical Mercury Level (ppm) | FDA Consumption Recommendation | Notes |
|---|---|---|---|
| Sardines | 0.013 | Best Choice (2-3 servings/week) | Excellent source of omega-3s, calcium. |
| Canned Salmon | 0.014 | Best Choice (2-3 servings/week) | Great for protein and omega-3s. Wild varieties generally lower. |
| Anchovies | 0.02 | Best Choice (2-3 servings/week) | High omega-3s; can be high in sodium. |
| Canned Light Tuna | 0.13 | Best Choice (2-3 servings/week) | A common choice, but mercury can vary from can to can. |
| Canned Albacore Tuna | 0.35 | Good Choice (1 serving/week) | Higher mercury than light tuna due to fish size. Limit intake. |
| Yellowfin Tuna | 0.35 | Good Choice (1 serving/week) | Higher mercury; also available fresh. |
| Mackerel (Spanish) | 0.35 | Good Choice (1 serving/week) | Spanish mackerel has moderate mercury; Atlantic and Pacific chub are lower. |
| Bigeye Tuna | 0.69 | Choices to Avoid | Very high mercury levels; not recommended. |
Which Canned Fish to Avoid (or Limit)
For the average consumer, moderation is key. However, some types of canned fish should be limited or avoided entirely, especially by pregnant women and young children. The FDA categorizes fish into "Best Choices," "Good Choices," and "Choices to Avoid".
- Canned Albacore Tuna: As shown in the table, albacore has significantly more mercury than canned light tuna. It is a "Good Choice" but should be limited to one serving per week.
- Bigeye Tuna: This type of tuna is typically used in sushi but can occasionally be canned or appear on menus. It is high in mercury and on the FDA's "Choices to Avoid" list.
- Spanish Mackerel: While generally healthier than tuna, Spanish mackerel can contain moderate mercury levels. Atlantic and Pacific chub mackerel are better options.
Guidelines for Healthy Consumption
To make informed choices about consuming canned fish while minimizing mercury exposure, consider these guidelines:
- Eat a variety of fish. Rotating between different species ensures a broader range of nutrients and prevents over-consumption of any single type of fish that may contain contaminants.
- Stick to smaller fish. Small, short-lived species like sardines, anchovies, and salmon have the lowest mercury levels.
- Choose canned light tuna (skipjack). If tuna is your preference, opt for canned light tuna over albacore. Some brands, like Safe Catch, test every individual tuna for mercury, offering extra peace of mind.
- Know your population group. The FDA and EPA provide specific recommendations for pregnant women, breastfeeding mothers, and young children, who are more susceptible to the harmful effects of mercury.
- Watch sodium intake. Many canned fish products are high in sodium. Look for low-sodium varieties packed in olive oil or water to manage salt intake.
Conclusion
When it comes to selecting canned fish with the least mercury, sardines, anchovies, and salmon are the clear winners. These smaller, shorter-lived species consistently have the lowest levels of mercury, providing a safe and nutritious source of protein, omega-3s, and other essential nutrients. While canned light tuna is a reasonable option, albacore and bigeye tuna should be consumed in moderation due to higher mercury concentrations. By making informed choices and diversifying your intake, you can enjoy the many health benefits of canned fish without unnecessary mercury exposure.
