Does cooking fish reduce mercury?

November 30, 2025 •

4 min read

Methylmercury, the toxic form of mercury found in fish, binds tightly to the muscle tissue and is not significantly affected by heat. This means that for the question, 'Does cooking fish reduce mercury?', the simple answer is no, it does not. The total amount of mercury in a fillet remains virtually unchanged through baking, frying, or steaming.

Quick Summary

Cooking methods like baking or frying do not reduce the total mercury content in fish. The metal is tightly bound to muscle proteins and is heat-stable. Safe consumption depends on choosing low-mercury fish and moderating intake, especially for at-risk groups.

Key Points

Cooking is Ineffective: Cooking fish at high temperatures does not remove or destroy the heat-stable methylmercury present in its muscle tissue.
Mercury Binds to Protein: Methylmercury is chemically bonded to the proteins in fish flesh, meaning it cannot be simply washed or cooked away.
Focus on Fish Selection: The most effective strategy for reducing mercury exposure is to choose fish species known to have lower mercury levels.
Choose Smaller Fish: Fish that are smaller, younger, and lower on the food chain generally contain less mercury than large, long-lived predators.
Bioaccessibility is Debated: While some lab studies suggest cooking might decrease how much mercury the body absorbs, this has not been reliably proven in real-world scenarios.
Risk Varies by Species: Mercury levels vary significantly between fish types, with large predators like shark and swordfish having the highest levels.
Check Local Advisories: Always check for local health advisories, particularly if consuming fish from specific local waterways, as contamination levels can differ.

The Truth About Mercury and Cooking

Many people assume that cooking fish at high temperatures can destroy or remove harmful contaminants, similar to how heat kills bacteria. However, this is not the case for mercury. The mercury in fish is primarily in the form of methylmercury, a stable organic compound that is resistant to the temperatures used in standard cooking methods. Because methylmercury binds to the proteins within the fish's muscle tissue, it cannot be washed away or cooked out. In some cases, cooking can even slightly increase the concentration of mercury on a per-weight basis as moisture is lost during the cooking process, thereby concentrating the remaining mercury.

How Mercury Enters and Accumulates in Fish

To understand why cooking is ineffective, it is important to know how fish become contaminated in the first place. This process involves bioaccumulation and biomagnification, which explain why larger, longer-lived predatory fish tend to have the highest mercury levels.

Environmental Release: Mercury is released into the environment from both natural sources (like volcanic activity) and human activities (such as coal burning and industrial waste).
Conversion to Methylmercury: Once in the water, bacteria convert inorganic mercury into the more toxic methylmercury.
Bioaccumulation: Tiny aquatic organisms absorb this methylmercury, which then accumulates in their bodies over time.
Biomagnification: As larger predatory fish eat smaller fish, the methylmercury accumulates at higher and higher concentrations up the food chain.

Bioaccessibility vs. Concentration: A Subtle Distinction

While cooking does not reduce the total mercury content, some studies suggest it may affect the bioaccessibility of mercury. Bioaccessibility refers to the amount of a substance that is released from the food matrix during digestion and made available for absorption by the body.

Some in-vitro (lab-based) studies have shown that certain cooking methods, particularly frying and baking, can reduce mercury bioaccessibility compared to eating raw fish. It is hypothesized that heat-induced changes to protein structures may make the mercury less available for intestinal absorption. For example, one study found that frying and boiling reduced mercury bioaccessibility by 60% and 40%, respectively, compared to raw fish. However, these findings are debated, and other studies using in-vivo (animal) models have found no significant change in overall mercury absorption, despite a potential reduction in bioaccessibility. Furthermore, factors like co-ingested foods (e.g., garlic or broccoli) and the type of fish can also influence bioaccessibility. Ultimately, relying on cooking to reduce mercury exposure is not a proven or reliable strategy.

Smart Fish Choices: Minimizing Mercury Exposure

Instead of focusing on cooking methods, the most effective way to minimize mercury exposure is to make informed choices about the types and quantities of fish you consume. The U.S. Food and Drug Administration (FDA) provides guidance on fish consumption, especially for vulnerable populations like pregnant women, nursing mothers, and young children.

High vs. Low Mercury Fish

This table outlines some common fish species and their relative mercury levels, based on FDA data.


Low Mercury (Enjoy Regularly)	High Mercury (Limit or Avoid)
Shrimp	Shark
Salmon	Swordfish
Canned Light Tuna	King Mackerel
Catfish	Tilefish (Gulf of Mexico)
Pollock	Bigeye Tuna
Sardines	Orange Roughy
Scallops	Marlin
Anchovies	Pike

General Guidelines for Fish Consumption

Eat a variety of seafood: Choosing a mix of species helps ensure you get a broad range of nutrients while mitigating the risk of exposure to a single contaminant.
Opt for smaller fish: Since mercury biomagnifies up the food chain, smaller fish that are lower on the food chain generally have less mercury.
Follow advisories: Check local fish consumption advisories, especially if you catch your own fish, as mercury levels can vary by location.
Trim fat for other contaminants: While it won't help with mercury, trimming fat and skin is effective for reducing exposure to other contaminants like PCBs.

Conclusion: Making Informed Choices

Does cooking fish reduce mercury? The scientific consensus is clear: no, it does not. The methylmercury in fish is heat-stable and binds permanently to the muscle tissue. While some studies suggest that cooking might reduce the bioaccessibility of mercury during digestion, this effect is debated and does not eliminate the mercury itself. Therefore, the safest and most effective strategy for managing mercury intake is to control the source. By choosing a variety of smaller, lower-mercury fish and being mindful of intake, especially for at-risk individuals, you can safely enjoy the many nutritional benefits of seafood. For specific guidance on consumption, always refer to updated advisories from trusted health organizations like the U.S. Food and Drug Administration.

How to Reduce Mercury Exposure When Eating Fish: A Summary

Prioritize Low-Mercury Options: Stick to fish like salmon, shrimp, and canned light tuna for regular meals.
Limit High-Mercury Fish: Restrict your consumption of larger predatory species such as shark, swordfish, and king mackerel.
Check Local Advisories: Consult state or local health department guidelines, particularly for fish caught locally.
Cook for Safety, Not Mercury Removal: Cook fish thoroughly to kill pathogens and ensure food safety, but understand it won't remove mercury.
Control Portion Sizes: Adhere to recommended portion sizes and weekly limits, especially for women of childbearing age and young children.

Low vs. High Mercury Fish Recommendations

Best Choices (Low Mercury): Anchovy, Catfish, Clam, Cod, Crab, Haddock, Herring, Oyster, Pollock, Salmon, Sardine, Scallop, Shrimp, Squid, Tilapia, Trout (Freshwater), Tuna (Canned Light). Eat 2-3 servings per week.
Good Choices (Higher Mercury): Bluefish, Halibut, Mahi Mahi, Monkfish, Snapper (freshwater), Tuna (Canned White/Albacore, Yellowfin). Eat one serving per week.
Choices to Avoid (Highest Mercury): King Mackerel, Marlin, Orange Roughy, Shark, Swordfish, Tilefish (from Gulf of Mexico), Bigeye Tuna. Avoid these fish, especially for at-risk groups.

Frequently Asked Questions

No, trimming the fat and skin from fish does not reduce mercury levels. Methylmercury accumulates primarily in the muscle tissue (the part you eat), not in the fat. While this method is effective for reducing other contaminants like PCBs, it does not work for mercury.

Mercury levels vary depending on the type of canned tuna. Canned 'light' tuna (often skipjack) is generally low in mercury. However, canned 'white' or albacore tuna typically has higher levels and should be eaten in moderation, especially by at-risk individuals.

Generally, smaller fish that are lower on the food chain have lower mercury levels. Good choices include salmon, shrimp, sardines, anchovies, pollock, and tilapia.

High mercury exposure, especially to methylmercury, is a powerful neurotoxin that can affect the brain and nervous system. Symptoms can include tremors, vision problems, and coordination issues. Fetuses and young children are particularly vulnerable to neurological damage.

Almost all fish contain at least trace amounts of mercury due to widespread environmental contamination. However, for most fish, the levels are very low and pose little risk to human health when consumed in moderation.

Yes, fish are an excellent source of protein, vitamins, and beneficial omega-3 fatty acids, which support heart and neurological health. For most people, the nutritional benefits of eating a variety of low-mercury fish outweigh the potential risks of mercury exposure.

No, soaking fish in milk, lemon juice, or any other marinades does not remove mercury. As the methylmercury is bound within the fish's tissue, external cleaning or soaking processes cannot draw it out effectively.

Yes, unborn infants and young children are especially vulnerable to the effects of methylmercury, which can harm their developing brains and nervous systems. Health authorities recommend that pregnant women, nursing mothers, and young children limit or avoid high-mercury fish.