Why I Avoid Certain Fish — Even at My Favorite Restaurants
- Christine Daecher, DO
- 12 hours ago
- 5 min read
Recently, I read about a local restaurant in my city featured in a national magazine. It’s a place I’ve been to several times and absolutely love. I usually order the branzino, one of my favorite dishes, anywhere I see it on the menu. What caught my attention this time was the mention of “stout wedges of local amberjack.” That phrase immediately made me pause — not because it didn’t sound delicious, but because it raised a red flag about mercury exposure.
Living on the Georgia coast means having access to an abundance of fresh, local seafood. Georgia’s coastal waters are considered some of the cleanest on the East Coast, yet even here, certain species are best eaten sparingly — or avoided altogether — because of mercury bioaccumulation.
“The larger and older the fish, the more mercury it accumulates over its lifetime.”
How Mercury Affects the Body
No amount of mercury exposure is truly safe — every form of mercury is poisonous. Mercury exists in three main forms: elemental mercury, inorganic salts, and organic compounds.
Elemental mercury (metallic mercury) is poorly absorbed through the gastrointestinal tract when ingested, but its vapor form is readily absorbed through inhalation.
Methylmercury, an organic mercury compound, is considered the most toxic form because approximately 90% of it is absorbed when ingested. This is the form that bioaccumulates in the food chain, particularly in large predatory fish.
Other forms of mercury are absorbed from the GI tract at much lower rates — typically only 2–10% — but can still be harmful with ongoing exposure.
Once in the body, mercury tends to accumulate in the brain, kidneys, and gastrointestinal organs. In the kidneys, it can contribute to hypertension and chronic kidney disease over time.
People who carry the ApoE4 allele (linked to a higher risk of Alzheimer’s disease) have reduced mercury-detoxifying capacity. In contrast, those with the ApoE2 allele tend to detoxify mercury more efficiently and have a lower risk of neurodegeneration.
High-Mercury Fish: What to Avoid
First, let’s talk about the problem with fish. Fish proteins bind more than 90% of the methylmercury we consume, which means that nearly all of the mercury present in fish becomes absorbed when we eat it.
Even more concerning, the methylmercury is bound so tightly to the fish’s muscle tissue that it cannot be removed by any cooking process — not by baking, grilling, frying, or boiling. Once the mercury is in the flesh, it stays there.
The larger and older a fish is, the more methylmercury it contains. Mercury is a persistent ocean contaminant — a legacy of industrial pollution that settles into the water and enters the food chain. Industrial sources of mercury tend to be elemental mercury, which upon entering the food chain either through vegetation, micro organisms, and, and other organisms becomes methylmercury.
Predatory “game fish” that feed on smaller fish accumulate methylmercury through bioaccumulation and biomagnification, making them the most concerning species.
Species to Limit or Avoid
Swordfish: Among the highest-mercury fish. During my functional medicine training, several attending physicians shared cases of severe mercury toxicity in patients who frequently ate swordfish — including professional chefs. I distinctly remember one case involving a chef who developed early-onset Parkinson’s disease after eating swordfish at his own restaurant one to two times per week for more than two years.Avoid swordfish. Always.
Tuna (all species): From albacore to yellowfin, all are high to moderately high in mercury. I now only eat canned tuna labeled “low mercury tested”, and even then, just once or twice a year.
Halibut: High in mercury and best limited to rare occasions.
Amberjack and other jacks: These large fish are high-mercury species. The “chunks” mentioned in that restaurant article likely came from a mature amberjack, meaning higher mercury exposure.
Grouper: Common in southern coastal waters and reefs but unfortunately high in mercury.
King mackerel: Extremely high mercury content; should be avoided.
Location Matters
Mercury levels vary greatly depending on where the fish was caught.
Tilefish: Low in mercury when caught in the Atlantic Ocean (≈0.14 ppm) but very high when caught in the Gulf of Mexico (≈1.12 ppm — higher than swordfish!).
Spanish mackerel: Lowest mercury in the North Atlantic, moderate in the South Atlantic, and high in the Gulf of Mexico (similar to tuna).
Pacific mackerel: Typically low mercury from the Pacific Ocean.
Overall, fish from the Gulf of Mexico tend to have higher mercury concentrations than those from the Atlantic.
Lower-Mercury Local Options
Not all local fish are high in mercury. Here are some of the safer, lower-mercury species commonly found in coastal Georgia waters:
Safe Seafood Guide: FDA/EPA Recommendations
Current recommendations for eating low-mercury fish are no more than two to three servings per week. A standard serving is only about 4 ounces of cooked fish — roughly the size of the palm of your hand — which is smaller than most restaurant portions.
Final Thoughts
When it comes to seafood, bigger isn’t better. The larger and older the fish, the higher its mercury content — no matter how fresh, local, or beautifully prepared it may be.
Eating fish is one of the great pleasures of coastal living, but being selective about species can go a long way in protecting long-term health, especially the brain, kidneys, and cardiovascular system.
Speckled Sea Trout Branzino-Style
Ingredients
1 whole sea trout, scaled and gutted (pectoral and ventral fins removed)
1 lemon, thinly sliced (reserve ¾ for juice)
1 small tomato, thinly sliced
¼ red onion, thinly sliced
2–3 Tbsp olive oil
Kosher salt and fresh-ground black pepper
½ tsp each: granulated garlic, oregano, thyme, basil, and dill (plus extra dill for garnish)
Preparation
Preheat oven to 400°F (200°C). Line a baking dish or sheet pan with parchment paper.
Prepare the trout: Pat the fish dry with paper towels. Season the cavity with salt, pepper, and a pinch of dill.
Stuff the cavity with the sliced lemon, tomato, and red onion.
Season the exterior: Sprinkle the top generously with salt, pepper, granulated garlic, oregano, thyme, basil, and dill.
Add oil and lemon: Drizzle with olive oil and squeeze the juice of ¾ of the lemon over the top. Scatter any extra vegetables around the fish.
Bake for 7 minutes. Remove from the oven, carefully flip the fish, and repeat seasoning and a light drizzle of olive oil on the second side.
Bake another 7 minutes, then move the pan to the top rack and broil on high for 3 minutes, until the skin is crisp and lightly browned.
Transfer to a serving plate, garnish with fresh dill and lemon slices, and pair with your favorite sides — such as roasted vegetables, a green salad, or herbed rice.
Resources:
Source: FDA & EPA “Advice About Eating Fish,” 2021 Update
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