Since the first caveman learned to sharpen a stick, fish have been an integral part of the human diet. Like most foods that have been around for millennia, the positive nutritional impact of eating fish far outweighs any theoretical health risks that it might bring. But to a growing and influential school of activist groups, fish isn’t just a source of vital nutrients. It’s a platform for fighting eco-battles and raising money.

Take the public skirmishes over mercury in swordfish, tuna, and other popular fish species. Some activist groups have a stake in needlessly scaring the public about mercury. Many hope to use the issue to generate support for tighter controls on coal-burning electric power plants. Some want to end long-line fishing in order to "protect" other marine species. Others believe fish have "rights." Groups like these make cynical use of government mercury-consumption guidelines to pollute our public discourse with stories of brain-damaged children and endangered pregnancies. But they never mention that these government fish advisories are designed with not just a double or triple safeguard, but a built-in ten-fold (that's 1000 percent!) margin of safety.

For instance, a typical pregnant woman who only slightly exceeds the Environmental Protection Agency's "Reference Dose" for mercury in her blood isn't in any danger. Neither is her unborn child. Alas, she might be protected by a 900-percent cushion instead of the 1,000-percent the rest of us enjoy. But she's still not likely to be in any danger. The EPA understands this, but it continues to multiply the theoretical risk by ten, desperate in its quest to protect us from ourselves.

Imagine what life would be like if the federal government applied this logic to other parts of our daily life. Speed limits would be set at just 6 or 7 miles per hour. Cushioned bike helmets would be bigger than bicycles. Airline passengers would have to pass through ten metal detectors before boarding a plane. The only sunscreen available for purchase would be SPF 150 and above. The "5 a day" program to promote fruit and vegetable consumption would be "50 a day" instead. Freeway lanes would be over 40 yards wide. And the Department of Transportation's new slogan would be "Wearing ten seat belts isn't just a good idea. It's the law!"

This approach -- crafting hyper-conservative, overcompensated health guidelines -- may be appropriate for internal policy debates at the EPA, but in the real world these things have consequences. Reporters can lose sight of reality. Politicians can grandstand. Activist groups can exaggerate the "crisis" of the day. And Americans can become needlessly frightened.

In 2003 Dr. Michael Bolger, Chief of the U.S. Food and Drug Administration's Contaminants Branch, said that "92 percent of women of child-bearing age already consume below [the EPA's mercury] reference dose, while the top 8 percent still have a safety margin of about eight-fold." And shortly after Bolger made this comment, the Centers for Disease Control and Prevention (CDC) released new data showing that only 5.6 percent, not 8 percent, of women of childbearing age -- and zero percent of American children -- exceeded the Reference Dose (that ten-fold safety-adjusted number).

Activist groups know that the "safety margin" Bolger described in 2003 makes our government's mercury advice hard to understand. But they continue to recklessly promote the idea that serious neurological disorders await anyone who dares cross the EPA's line in the sand by eating too much fish.

The unfortunate truth is that Americans should be eating more fish, not less. A landmark November 2005 Harvard study warned about the dangers of over-reacting to government fish consumption advisories. "An advisory is like a medication," the study's lead author told one medical reporter. "It has a therapeutic effect, but it also has side effects."

Indeed, the Omega-3 fatty acids found in most fish species can help prevent heart attacks, strokes, Alzheimer's disease, arthritis, breast and prostate cancer, and many other conditions. When government mercury advisories encourage Americans (especially women) to eat less fish, that's no cause for celebration. There are no scientifically documented cases of Americans developing mercury poisoning from eating commercially available fish, but the mass media is more likely to repeat dire (if baseless) health warnings than to remind Americans of what's good in their diets. And ominous health scare stories generally originate with agenda-driven environmental activist groups, some of whose sympathizers even wind up with jobs inside government agencies.

While some activists are dedicated to whipping up public panic about mercury, others run multi-million-dollar boycotts of this fish or that, claiming that a given species is near the brink of commercial extinction. At the same time, they hope against hope that journalists and consumer advocates won't bother to look into whether the current "poster fish" is actually endangered. And animal rights groups -- including at least one that masquerades as a medical and nutrition charity -- are so morally opposed to the idea of eating fish that they'll say anything if it just might turn the public into vegetarians.

The politics of fish get stranger with each passing year. Hidden agendas and junk science abound, and there are just two things you can be sure of: Fish is good for you, and the real health risk is in letting social activists craft health policy for the rest of us.