Amber Waves Of Altered Genes

"If I didn't believe it was safe, I wouldn't grow it," Doran Zumbach, a successful farmer in Iowa, told CBS News Correspondent Wyatt Andrews.

Zumbach hates it when someone accuses him of growing "Frankenstein food." "I think there s a huge amount of scare tactic there," he says.

What Zumbach is growing is genetically modified food -- corn that has been gene-spliced with a different organism. It's a forced genetic marriage between corn and a bacterium called Bt.

The Bt gene is inserted in the plant. It makes the plant toxic to an insect called the Corn Borer, but leaves the corn safe for human consumption. Zumbach argues the modified corn is much better for the environment because it eliminates the need for pesticides against the insect.

"Historically we've applied a lot of insecticide to kill Corn Borers," he says. "With the Bt gene inserted in the plant, I don't have to do that."

It's just the beginning of the genetically modified or "GM" future. Today it's pest resistant plants, but soon, there will be health foods. Soy spliced with the nutrients of olive oil, vegetables with more vitamin A, and potatoes that produce pharmaceutical drugs.

American farmers are planting these genetically altered crops whole hog. Today, half of the soy beans, 40 percent of the corn and an increasing number of potatoes are all being grown with this genetically engineered seed.

There are no labels to tell you, but thousands of foods in the store -- from corn-fed cattle, to corn flakes now comes from GM crops. Americans eat them every day.

In Europe and especially England, critics call it "Franken-food."

Prince Charles questions its safety, and at the British Medical Association, Dr. Vivienne Nathanson warns that altered DNA in food could produce allergies as well as other health problems.

"The fact there is no demonstrable effect on human health thus far does not mean that something is risk free," she says.

John Fagan, an American scientist whose laboratory tests genetic foods for European companies also believes GM foods need more research. "In fact every time you put in a gene it's causing genetic mutations to the existing genes of that organism, and so there are unexpected side effects that can come out of this process."

Hugh Grant is the president of agriculture at Monsanto, the largest U.S. producer of genetic seeds. He calls the fears expressed by critics unfounded.

He contends that genetically modified foods have been tested on humans, and that "these are proteins that are broken down as you ingest them."

Monsanto, which showed CBS News how the crops are developed, insists the plants are screened and tested for harmful proteins long before they sell the seeds to farmers.

"The government has given them an absolutely clean bill of health and they have sailed through the regulatory system in the U.S. and have been signed off as safe," Gransays.

Still, the speed of this revolution -- from nothing four years ago to tens of millions of acres today -- has put some farmers in a bind. They're growing food that some of their customers don't want; customers who don't trust the altered genetic makeup of the amber waves of grain.