The origins of the healthiest protein on the planet are as murky as some of the waters it swims in. We rarely know where in the world our fish comes from, whether it was farmed, or how it was caught. As recent studies have shown, due to toxic, mislabeled fish, what we end up eating can also be detrimental to our health. In his new book, 'The Perfect Protein,' Andy Sharpless outlines a straightforward plan: "Eat wild seafood. Not too much of the big fish. Mostly local." By clearly following through on this precept, with backing research from the fish conservation nonprofit Oceana, he provides a game plan toward eating the healthiest meat around.

Eat Mostly Wild Fish
In the wilds of the ocean, fish thrive, growing fat on a diet of algae and other creatures. On a fish farm, the animals usually aren't as rich in natural omegas and can be higher in toxins. The reason: Carnivorous seafood like salmon and shrimp are fed a combination of fish oil and grain, and don't have the space to flex their muscles. On the other hand, some mostly vegetarian fish, such as tilapia and catfish raised in zero-waste ponds, can be even healthier than their wild counterparts, but only if they are bred in the U.S. – Chinese farms, for instance, offer polluted ponds.

Avoid "Organic"
Much like the "all-natural" strawberry, the term "organic," when used to describe salmon, for example, doesn't mean much. "The truth is that there is no such thing as an organic wild fish," says Sharpless, who is CEO of Oceana. If you do find organic fish, it almost always means it's farmed in Europe, with feed that might comply with organic standards (although that's not a given; no fishery has officially been certified by a U.S. authority). "If you have a choice between wild and organic," he says, "choose wild."

Buy Smaller Fish
Five species in the ocean are so contaminated by mercury that the Food and Drug Administration has issued a health warning about them. All are large fish: tuna, swordfish, tilefish, king mackerel, and shark. Why? "Mercury bioaccumulates over time in ocean fish, which means that the many ocean fish that live relatively short lives are safer to eat," he says. Toxins like dioxins and PCBs do the same. This doesn't mean we all have to eat nothing but anchovies (although they are one of the most omega- and calcium-rich species on the planet, says Sharpless). Simply picking a smaller tuna will help minimize toxins.

See also: The Five Safest Fish to Eat