You cannot fully remove mercury from fish. The mercury in seafood, primarily in a form called methylmercury, binds directly to the proteins in fish muscle tissue at a molecular level. No home cooking method, trimming technique, or soaking process will eliminate it entirely. That said, certain preparation methods can reduce how much mercury ends up in your body, and choosing lower-mercury fish in the first place is the most effective strategy.
Why Mercury Is So Hard to Remove
Mercury in fish isn’t sitting on the surface or stored in the fat the way other contaminants like PCBs and dioxins are. With those chemicals, you can trim away fatty tissue and cut your exposure roughly in half. Mercury works differently. It bonds to sulfur-containing amino acids in the fish’s muscle protein with an extremely strong chemical attraction. Think of it less like dirt on a surface and more like dye soaked into fabric. The bond is so tight that researchers at Chalmers University of Technology, working on a special mercury-absorbing packaging for canned tuna, found that the forces binding mercury within tuna tissue actively prevented it from being released, even when surrounded by a material designed to pull it out.
This is why the Michigan Department of Health and Human Services states plainly in its fish consumption guidelines: “Mercury cannot be removed from the fish.” Trimming fat, removing skin, and cleaning fish thoroughly are excellent practices for reducing PCBs and dioxins, but they do essentially nothing for mercury.
Cooking Methods That Help (a Little)
While no cooking method eliminates mercury, some do reduce your exposure. Research published in Current Research in Food Science tested four preparation methods on fish and found that baking and frying lowered both mercury concentration and the amount of mercury your body actually absorbs. The reduction comes partly from moisture loss during high-heat cooking: as water leaves the fish, some mercury goes with it. The more intense the heat treatment, the greater the effect.
Steaming and marinating, on the other hand, actually increased mercury concentration in the cooked fish by nearly 20% compared to raw samples. Steaming retains most of the moisture, so the mercury stays concentrated in the tissue. Marinating had a similar effect. Among all methods tested, baked fish had the lowest amount of mercury available for your body to absorb, followed by steamed, fried, marinated, and smoked fish.
The practical takeaway: baking or frying fish at high temperatures is slightly better than eating it raw, steamed, or marinated if mercury is your concern. But the reduction is modest, not transformative.
Acidic Washing Before Cooking
One laboratory technique has shown more dramatic results. Researchers tested washing raw fish fillets in acidic solutions and found that the right combination of low pH, a small amount of salt, and a short soak could reduce mercury by up to 81%. The optimal conditions were a solution with a pH around 2.8 (roughly the acidity of lemon juice), 0.5% salt, and a soaking time of about 13 and a half minutes.
This sounds promising, but there are important caveats. This was a controlled lab study, not a home kitchen technique. Soaking fish in highly acidic liquid for that long would significantly change its texture and flavor, essentially beginning to “cook” or cure the flesh. It also hasn’t been validated as a practical consumer recommendation by any food safety authority. Still, it suggests that a brief soak in citrus juice or vinegar before cooking could have some modest benefit, even if you won’t achieve the 81% reduction seen under optimized lab conditions.
Selenium’s Protective Role
One of the more useful things that naturally occurs in fish is selenium, a mineral that directly counteracts mercury’s harmful effects in your body. Most fish have a selenium-to-mercury ratio greater than 1.0, meaning they contain more selenium than mercury. When this ratio stays above 1.0, the selenium helps prevent mercury from doing damage. Field studies have shown that higher selenium concentrations are associated with reduced mercury accumulation in animals.
This doesn’t “remove” mercury from the fish, but it does change the equation inside your body. Fish that are naturally high in selenium (like yellowfin tuna, sardines, and shrimp) offer a degree of built-in protection. The fish you want to be cautious about are the ones where mercury levels are high enough to overwhelm the selenium, which tends to happen in large, long-lived predatory species.
Choosing Lower-Mercury Fish
Since you can’t reliably strip mercury from fish after it’s caught, your most powerful tool is choosing species with less mercury to begin with. The FDA and EPA classify fish into three tiers based on mercury content.
Best choices (lowest mercury) include salmon, shrimp, cod, tilapia, catfish, sardines, anchovies, trout, pollock, crab, scallops, squid, herring, and canned light tuna. You can safely eat two to three servings per week from this group.
Good choices (moderate mercury) include halibut, mahi mahi, snapper, grouper, Chilean sea bass, albacore tuna (canned or fresh), yellowfin tuna, monkfish, and bluefish. One serving per week is the recommended limit.
Fish to avoid due to the highest mercury levels are king mackerel, marlin, orange roughy, shark, swordfish, Gulf of Mexico tilefish, and bigeye tuna. These large predators accumulate mercury over their long lifespans, and the concentrations are high enough that no cooking method will bring them into a safe range for regular consumption.
What Actually Works in Practice
If you’re trying to minimize mercury exposure while still eating fish, here’s what the evidence supports. First, build your meals around the “best choice” species listed above. Second, bake or fry fish at high heat rather than steaming, smoking, or eating it raw, since this offers a small but real reduction in the mercury your body absorbs. Third, drain the liquid from canned tuna rather than using it, as some mercury does migrate into the packing liquid. Fourth, eat a varied diet of different fish species rather than relying heavily on one type, which prevents you from accumulating mercury from a single high-exposure source.
For PCBs and dioxins, the old advice about trimming skin and belly fat still applies and remains effective. But for mercury specifically, the fish you choose matters far more than how you prepare it. A perfectly baked swordfish steak will still contain dramatically more mercury than a simply steamed piece of salmon.