Despite their snazzy Internet campaigns, well-publicized investigations, and scary language (“Tuna Roulette!”, “The Mercury Menace!”), green-group activists can’t change the simple fact that the mercury levels in the fish we typically eat pose zero health risk to consumers. But there’s more to the story. Ladies and gentlemen, meet selenium.

Naturally found in abundance in most fish, selenium is what scientists call an “antagonist” to mercury. How selenium cancels out mercury is still up for debate. But scientists at the Environmental Protection Agency, National Oceanic and Atmospheric Administration, and several major universities have established that it does.

The top 25 sources of selenium in the American diet include 16 different kinds of fish. In fact, the average fish on your plate has a selenium-to-mercury ratio of over five to one. So your tuna sandwiches, salmon croquettes, and swordfish steaks are perfectly safe.

Activists often cite a study of residents in Denmark’s Faroe Islands as “proof” that the fish you eat can harm you. Environmental activist groups that spread fish fears don’t talk about selenium. They’d rather frighten you with a hypothetical health risk, no matter how small that risk is. But as we explain at FishScam.com, it’s irresponsible to talk about mercury toxicity without also mentioning the protective effects of selenium.