Nutrition Diet: What fish has the highest amount of mercury?

According to data from the FDA, Tilefish from the Gulf of Mexico has one of the highest mean mercury concentrations, exceeding the agency's recommended limit. Understanding what fish has the highest amount of mercury is crucial for managing your intake and ensuring seafood remains a healthy part of your diet.

Quick Summary

Mercury accumulates in larger, longer-lived predatory fish like Gulf of Mexico Tilefish, shark, and swordfish due to biomagnification, posing a health risk to consumers, especially pregnant women and children. The FDA provides guidelines on which fish to avoid or limit due to high mercury levels.

Key Points

• High-Mercury Offenders: The fish with the highest mercury content are typically large, long-lived predators like Tilefish (Gulf of Mexico), shark, swordfish, king mackerel, and bigeye tuna.

• Low-Mercury Alternatives: Safer choices include salmon, sardines, shrimp, pollock, catfish, and canned light tuna, which contain significantly lower levels of mercury.

• Biomagnification is the Cause: High mercury levels in fish are a result of biomagnification, where mercury concentrations increase as they move up the aquatic food chain.

• Vulnerable Populations Need Caution: Pregnant women, breastfeeding mothers, and young children are most at risk from mercury's neurotoxic effects and should follow specific FDA consumption advice.

• Diversify Your Diet: Eating a variety of different low-mercury fish, rather than just one type, can help balance nutritional intake and minimize mercury exposure.

• Check for Local Advisories: For locally caught fish, it is crucial to check for specific advisories issued by state and local health departments.

The Science of Mercury in Fish

Mercury is a naturally occurring element, but human activities, such as industrial pollution and coal burning, increase its presence in the environment. In aquatic ecosystems, this element is converted into methylmercury by bacteria. Methylmercury is a highly toxic organic compound that fish and other seafood can absorb as they feed. The process of mercury accumulation in fish is a significant health concern for consumers, particularly those who eat fish frequently.

How Does Mercury Get Into Fish?

It begins at the bottom of the food chain. Algae and other small organisms absorb methylmercury from the water and sediment. When smaller fish consume these organisms, they absorb the mercury, which then accumulates in their tissues. Since fish excrete mercury very slowly, the levels build up over their lifespan.

The Process of Biomagnification

Biomagnification is the process by which the concentration of toxins, like methylmercury, increases as it moves up the food chain. For example, a larger predatory fish eats many smaller fish, each containing a small amount of mercury. The predatory fish absorbs the mercury from all its prey, leading to a much higher concentration in its own body tissue. This is why longer-lived, larger predatory species consistently have the highest mercury levels. When humans eat these larger fish, they become the final link in this biomagnification chain, increasing their own potential exposure to harmful levels of mercury.

What Fish Has the Highest Amount of Mercury?

Based on FDA advisories and data from commercial fish testing, several species stand out for their particularly high mercury content and should be avoided or limited, especially by vulnerable populations such as pregnant women, breastfeeding mothers, and young children.

Fish to Avoid (Highest Mercury Levels)

• Tilefish (Gulf of Mexico): This species consistently ranks at the top for mercury contamination, with some samples exceeding 1 part per million (ppm). Atlantic Tilefish typically has lower levels.
• Shark: As apex predators, sharks accumulate high levels of mercury throughout their long lifespans.
• Swordfish: Another large, predatory fish with significantly high mercury content.
• King Mackerel: This large species of mackerel is known to have high mercury levels.
• Bigeye Tuna: While all tuna contains mercury, bigeye tuna is known for having higher levels compared to other varieties like canned light tuna.
• Marlin: Similar to swordfish and shark, this is a large, predatory fish with elevated mercury concentrations.
• Orange Roughy: A long-lived deep-sea fish that accumulates mercury over its lifespan.

Safer Seafood Choices (Lower Mercury Levels)

Fortunately, many fish and shellfish are low in mercury and safe to consume regularly as part of a healthy diet. The FDA and EPA categorize these as "Best Choices.".

Here is a list of some of the best choices for low-mercury seafood:

• Salmon (Wild and Farmed)
• Sardines
• Shrimp
• Scallops
• Catfish
• Pollock
• Tilapia
• Haddock
• Cod
• Canned Light Tuna (Skipjack)

Comparison of Mercury Levels in Common Seafood

The following table illustrates the variation in mercury levels across different types of seafood, using data from sources like Healthline and the FDA. Mercury levels are often expressed in parts per million (ppm).

Seafood Type	Average Mercury (ppm)	Consumption Category	Notes
Tilefish (Gulf of Mexico)	1.123	Avoid	Very high mercury content.
Swordfish	0.995	Avoid	High mercury from biomagnification.
Shark	0.979	Avoid	Top predator with high accumulation.
King Mackerel	0.730	Avoid	High mercury levels.
Bigeye Tuna	0.689	Avoid	Higher mercury than other tunas.
Canned Albacore Tuna	0.350	Good Choice	Higher mercury than light tuna.
Halibut	0.241	Good Choice	Moderate mercury content.
Cod	0.111	Best Choice	Low mercury content.
Salmon	0.022	Best Choice	Very low mercury content.
Sardines	0.013	Best Choice	Very low mercury content.
Shrimp	0.001	Best Choice	One of the lowest mercury levels.

FDA Guidelines for Safe Fish Consumption

The FDA and EPA provide specific advice to help people make healthy and safe seafood choices. Their recommendations focus on balancing the nutritional benefits of fish, such as high protein and omega-3 fatty acids, with the risks of mercury exposure.

Who is Most at Risk?

Certain populations are particularly vulnerable to the harmful effects of methylmercury, a potent neurotoxin. The developing nervous systems of fetuses and young children are most at risk, as high mercury exposure can negatively impact cognitive thinking, memory, and motor skills. For this reason, pregnant or breastfeeding women and young children are advised to be especially cautious about their seafood consumption.

Recommended Consumption Levels

For most people, the FDA and EPA recommend eating 2 to 3 servings of a variety of fish per week, choosing options from their "Best Choices" list. A serving size is typically 4 ounces before cooking. Those in higher-risk groups are advised to limit their total weekly seafood intake to 8 to 12 ounces and stick primarily to the "Best Choices" list.

How to Make Smart Seafood Choices

Making informed decisions about the fish you eat can help you minimize mercury exposure while still reaping the health benefits of seafood.

Wild vs. Farmed Fish and Mercury

Studies have found that farmed fish often contain lower levels of mercury than their wild-caught counterparts. For example, mercury levels in farmed catfish and salmon have been found to be significantly lower than in wild varieties. This is likely due to the controlled diets and rapid growth rates in aquaculture settings. However, it is always best to choose smaller species that are lower on the food chain, regardless of whether they are wild or farmed, to minimize mercury exposure.

Reading Local Fish Advisories

If you consume locally caught fish from lakes, rivers, or coastal areas, it is important to check for local advisories. State and local health departments often issue warnings about contaminants, including mercury, in fish from specific bodies of water. These advisories can vary based on local pollution sources and differ from general federal guidelines.

Dietary Diversity and Your Health

Don't let the fear of mercury prevent you from enjoying fish, as it is an excellent source of lean protein, healthy fats, and other nutrients. The key is to diversify your choices. By varying the types of fish and seafood you eat, you can balance your mercury intake while still getting the nutritional benefits. This approach ensures you do not consume a disproportionately high amount of mercury from any single source. The FDA offers a detailed list of fish grouped by mercury levels to aid consumers in making informed decisions for a balanced diet. You can find more information about eating fish safely at the FDA's website: Advice about Eating Fish.

Conclusion: Balancing Nutrition and Safety

Ultimately, understanding what fish has the highest amount of mercury allows consumers to manage their intake effectively. While large, long-lived predatory fish like Tilefish (Gulf of Mexico), shark, and swordfish should be avoided or limited, a wide array of smaller, low-mercury fish and shellfish offers excellent nutritional benefits. By following FDA and EPA guidelines, diversifying your seafood choices, and being mindful of local advisories, you can continue to enjoy the health benefits of seafood while minimizing any potential risk from mercury exposure.

Frequently Asked Questions

Which specific type of fish contains the absolute highest level of mercury?

According to the FDA, Tilefish from the Gulf of Mexico has the highest average mercury concentration among commonly tested fish and should be avoided entirely.

Why do some fish have higher mercury levels than others?

Larger, older, and predatory fish tend to have higher mercury levels due to a process called biomagnification. They accumulate mercury from the smaller fish they eat over a longer lifespan.

Is it safe for pregnant women to eat fish?

Yes, but with caution. The FDA advises pregnant women to eat 2 to 3 servings a week of low-mercury fish from the 'Best Choices' list, while completely avoiding high-mercury fish.

What are the health risks of mercury poisoning from fish?

Symptoms of methylmercury poisoning can include neurological and behavioral issues, memory loss, tremors, loss of coordination, and impaired speech or hearing, especially affecting the developing nervous systems of children.

Does cooking fish remove mercury?

No, cooking fish does not remove mercury. The metal is bound to the proteins in the fish tissue and is not affected by heat.

Is canned tuna high in mercury?

The mercury level in canned tuna depends on the type. Canned light tuna, which typically uses smaller skipjack, is considered a 'Best Choice' with low mercury. Canned albacore ('white') tuna has higher mercury and should be limited.

Is farmed fish a safer option regarding mercury?

Yes, studies have shown that farmed fish generally have lower mercury levels than their wild-caught counterparts, partly due to controlled diets and faster growth rates.