What’s the Deal With Mercury in Fish?

I’m so confused about fish—I’ve heard that fish can be a really healthy source of protein, but I’ve also heard that some varieties are high in mercury and other contaminants. What fish are safe and healthy for me to eat?

I hear you—choosing a fillet of fish can be daunting when you’re worried about mercury levels and getting the most nutritional bang for your buck. But there’s no reason to think all fish are created equal, and if you skip seafood altogether, you’re missing out on tons of protein and omega-3 fatty acids.

Let’s switch gears for a second and think about fruits and vegetables. Although they’re all plants, each fruit and vegetable has different nutritional benefits, including sugar content, fat content, vitamins, and minerals. The same is true for fish.

As we have become more dependent on industrial trades, our mercury emissions have skyrocketed. According to one 2014 study, mankind has flooded the oceans with tens of thousands of tons of mercury in the last few hundred years. When mercury enters the oceans, it’s usually more concentrated near the surface of the water—where fish live and absorb this heavy metal.

To make sure you’re getting the healthiest seafood out there, look for wild-caught fish. Farmed fish are often fed with unnatural foods, exposed to toxins in dirty water, and tend to yield fewer nutritional benefits.  Although it’s fairly low in mercury, farmed tilapia is one of the worst options. These fish are not only extremely low in omega-3 fatty acids (compared to salmon), but they’re fed a terrible diet pumped full of antibiotics and hormones. No thank you!

Instead, choose wild salmon, sardines, and trout—all great choices. These fish are low in mercury, but high in protein and healthy fats. Some of the fish with the highest levels of mercury are grouper, swordfish, shark, ahi tuna, and marlin. The dangerous level of mercury exposure outweighs the health benefits of eating these types of fish, so it’s better just to avoid them altogether.

The takeaway here is always stick to wild-caught fish low in mercury, such as salmon, herring, mackerel, sardines, and trout). Some brands—like Safe Catch—also produce tuna low enough in mercury that it’s safe to eat. I recommend eating these types of fish at least once a week to get all those good-for-you fats and proteins. Before you head to the seafood counter at the market, check out the Monterey Bay Aquarium’s Seafood Watch list—it’s a great resource you can use to make sure you’re eating only the safest, healthiest fish.

Photo credit: Paul Delmont