It's not what we don't know that causes us trouble. It's what we know that isn't so. Whichever famous writer said that (it's been attributed to many), what he said carries truth.

What are some of the things we know that aren't so? Here's one: Grass-fed "free-range" beef cattle are better for the environment—and for you—than factory-farmed corn-fed cattle. It does seem to make sense that the steer raised in the more "natural" environment would be better for the world.

Michael Pollan, the prolific food author and activist, wrote in The New York Times that "what was once a solar-powered ruminant (grass-fed steer) (has been turned) into the very last thing we need: another fossil-fuel machine." How so? Farmers burn fossil fuels to ship corn to feed cows instead of letting them eat what's naturally under their feet.

Restaurants serving burgers supposedly made from grass-fed beef self-servingly claim their foods are healthier for the planet. The American Grassfed Association—surprise, surprise—says its cattle are better for the environment because harmony is created between the land and the animals.

People believe. Nobody likes the idea of cattle jammed into feedlots. When we asked people which kind of cattle were better, we got the expected answers:

"Free roaming."

"Cows should be outside."

"Free-roaming grass-fed cows, because you've got happy cows. They've lived a happy life out in sunshine."

It's logical to think that grass-fed steers might be better for the environment, but so often what sounds logical is just wrong.

Don't believe me? Dr. Jude Capper, an assistant professor of dairy sciences at Washington State University, has studied the data.

Capper said: "There's a perception out there that grass-fed animals are frolicking in the sunshine, kicking their heels up full of joy and pleasure. What we actually found was from the land-use basis, from the energy, from water and, particularly, based on the carbon footprints, grass-fed is far worse than corn-fed."

How can that be?

"Simply because they have a far lower efficiency, far lower productivity. The animals take 23 months to grow. (Corn-fed cattle need only 15.) That's eight extra months of feed, of water, land use, obviously, and also an awful lot of waste. If we have a grass-fed animal, compared to a corn-fed animal, that's like adding almost one car to the road for every single animal. That's a huge increase in carbon footprints."

Once again, modern technology saves money and is better for the earth. By stuffing the feedlot animals with corn, farmers get them to grow faster. Therefore they can slaughter them sooner, which is better for the earth than letting them live longer and do all the environmentally damaging things natural cows do while they are alive.

"Absolutely right," Capper said. "Every single day, they need feed, they need water, and they give off methane nitrous oxide—very potent greenhouse gases that do damage."

But what about damage to people? Some advocates of grass-fed beef claim that the more naturally raised animals are healthier to eat.

"There is absolutely no scientific evidence based on that. Absolutely none," she replied. "There is some very slight difference in fatty acids, for example, but they are so minor that they don't make any significant human health impact."

But what about those hormones the cows are given? Surely that cannot be good for us.

"What we have to remember is every food we eat—whether it's tofu, whether it's beef, whether it's apples—they all contain hormones. There's nothing, apart from salts, that doesn't have some kind of hormone in them."

So the next time you reach for that package of beef in the grocery store tagged with all the latest grass-fed, free-range lingo, remember: Not only does it often cost twice as much, but there's no evidence it's better for the environment or better for you.

It's just another food myth.

John Stossel is host of Stossel on the Fox Business Network. He's the author of Give Me a Break and of Myth, Lies, and Downright Stupidity. To find out more about John Stossel, visit his site at johnstossel.com.

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