Ahi steak. Akami sashimi. Albacore on sourdough. Whether you smoked yellowfin on the grill or spread skipjack on a sandwich, chances are you’ve had tuna recently.

On average, Americans eat around two pounds of the fish per year, more than any other seafood except for shrimp and salmon. And for good reason: Tuna is tasty and versatile, and the canned variety costs as little as a dollar.

But is it good for you? Should you be worried about its mercury content? And what about the health of our oceans? Here’s what to know before you pop open that next can for lunch.

Tuna is about as nutritious as a food can be.

It’s packed with protein, minerals and vitamins, said Chris Vogliano, a dietitian and research director at the educational nonprofit Food and Planet. It has more selenium than just about any other meat. It’s also low in fat, Dr. Vogliano noted — but that means it has fewer omega-3 fatty acids than some other seafood.

There’s not a huge nutritional difference between canned tuna, sushi and a tuna steak, he added. Cooking the fish might lower its vitamin D, and the canning process might leach out a few nutrients, he said, but its nutritional value is largely the same.

Tuna’s one big health drawback, experts say, is the risk posed by mercury, a neurotoxin. This heavy metal enters the ocean mostly from human activities like burning fossil fuels. It’s absorbed by small organisms and works its way up the food chain and accumulates in bigger, longer-lived species — like sharks, swordfish and, yes, tuna.

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