That phrase showed up, for instance, a few weeks ago, at a big farm convention in Decatur, Ill. The seed and chemical company DuPont set up a wall with a question printed at the top in big capital letters: "How are you making a difference to feed the world?"

The company invited people to answer that question, and thousands of them did. They wrote things like "raising cattle," "growing corn and beans," "plant as much as possible."

Kip Tom, who grows corn and soybeans on thousands of acres of Indiana farmland, says he's very aware of the fact that the world has more and more people, demanding more food. Yet there are fewer and fewer farmers, "and it's the duty of those of us who are left in the business, us family farmers, to help feed that world."

That means growing more food per acre, he says, which requires new and better technology: genetically engineered seed, for instance, or pesticides.

And this is why the words "feed the world" grate on the nerves of people who believe that large-scale, technology-driven agriculture is bad for the environment and often bad for people.

Margaret Mellon, a scientist with the environmental advocacy group Union of Concerned Scientists, recently wrote an essay in which she confessed to developing an allergy to that phrase. "If there's a controversy, the show-stopper is supposed to be, 'We have to use pesticides, or we won't be able to feed the world!'" she says.

Mellon says it's time to set that idea aside. It doesn't answer the concerns that people have about modern agriculture — and it's not even true.

American-style farming doesn't really grow food for hungry people, she says. Forty percent of the biggest crop — corn — goes into fuel for cars. Most of the second-biggest crop — soybeans — is fed to animals.

Growing more grain isn't the solution to hunger anyway, she says. If you're really trying to solve that problem, there's a long list of other steps that are much more important. "We need to empower women; we need to raise incomes; we need infrastructure in the developing world; we need the ability to get food to market without spoiling."

It seemed that this dispute needed a referee. So I called Christopher Barrett, an economist at Cornell University who studies international agriculture and poverty.

"They're both right," he said, chuckling. "Sometimes the opposite of a truth isn't a falsehood, but another truth, right?"

It's true, he says, that bigger harvests in the U.S. tend to make food more affordable around the world, and "lower food prices are a good thing for poor people."

For instance, Chinese pigs are growing fat on cheap soybean meal grown by farmers in the U.S. and Brazil, and that's one reason why hundreds of millions of people in China are eating much better than a generation ago. They can afford to buy pork. So American farmers who grow soybeans are justified in saying that they help feed the world.

But Margaret Mellon is right, too, Barrett says. The big crops that American farmers send abroad don't provide the vitamins and minerals that billions of people need most. So if the U.S. exports lots of corn, driving down the cost of corn meal, "it induces poor families to buy lots of corn meal, and to buy less in the way of leafy green vegetables, or milk," that have the key nutrients. In this case, you're feeding the world, but not solving the nutrition problems.

Arnot, from the Center for Food Integrity, recently did a survey, asking consumers whether they think the U.S. even has a responsibility to provide food to the rest of the world. Only 13 percent of these consumers strongly agreed.

In focus groups, many people said that if feeding the world means more industrial-scale farming, they're not comfortable with it.

This is not a message farmers like to hear. "It is a real sense of frustration for farmers that 'feeding the world' is no longer a message that resonates with the American public," Arnot says.

He tells farm groups that they'll have to find another message. They'll need to show that the way they grow food is consistent with the values of American consumers.

Copyright 2013 NPR.

Center for Food IntegrityCenter for Food Integrity

American Farmers Say They Feed The World, But Do They?