TRENTON, N.J. — Can animal genes be jammed into plants? Would tomatoes with catfish genes taste fishy? Have you ever eaten a genetically modified food?

The answers are: yes, no and almost definitely. But according to a survey, most Americans couldn't answer correctly even though they've been eating genetically modified foods — unlabeled — for nearly a decade.

"It's just not on the radar screen," said William Hallman, associate director of the Food Biotechnology Program at the Rutgers Food Policy Institute, which conducted the survey.

Today, roughly 75 percent of U.S. processed foods — boxed cereals, other grain products, frozen dinners, cooking oils and more — contain some genetically modified, or GM, ingredients, said Stephanie Childs of the Grocery Manufacturers of America.

Despite dire warnings about "Frankenfoods," there have been no reports of illness from these products of biotechnology. Critics note there's no system for reporting allergies or other reactions to GM foods.

Nearly every product with a corn or soy ingredient, and some containing canola or cottonseed oil, has a GM element, according to the grocery manufacturers group.

In the Rutgers survey, less than half the people interviewed were aware GM foods are sold in supermarkets. At the same time, more than half wrongly believed supermarket chicken has been genetically modified.

So far, nonprocessed meat, poultry, fish and dairy products, and fruits and vegetables (both fresh and frozen) are not genetically modified.

GM food first hit supermarkets in 1994, with the highly touted Flavr Savr tomato, altered to give it a longer shelf life and better flavor. It flopped, in part due to disappointing taste, and disappeared in 1997, said Childs.

By 1995, farmers in several countries had planted millions of acres of GM corn and soybeans, and processed products containing them were in grocery stores.

Genetic modification of crops involves transferring genes from a plant or animal into a plant. Nearly all GM changes so far are to boost yields and deter insects and viruses, cutting the use of pesticides, thus making farming more productive and affordable — a particular aid to developing nations.

More than 80 percent of the soy and 40 percent of the corn raised in this country is a GM variety. Global plantings of biotech crops — mostly corn and soybeans and much of it for animal feed — grew to about 200 million acres last year, about two-thirds of it in the United States.

The one billionth acre will be planted this spring, according to the Biotechnology Industry Organization.

Experts say within several years there will be new GM foods with taste and nutrition improvements: cooking oils with less trans fat, tastier potatoes and peanuts that don't trigger allergies.

At North Carolina State University, one of the biggest U.S. plant breeding programs, scientists are developing drought-tolerant wheat and are a couple years from field testing GM peanuts that have no life-threatening allergens, said Steven Leath, associate dean for health research.

At Rutgers University's agricultural college, plant biology professor Nilgun Tumer and colleagues modified potatoes to better keep their flavor when processed as french fries and to limit browning when sliced, but she said farmers haven't adopted the new varieties. Now her team is trying to give tomatoes a gene to make a compound that helps prevent cancer and osteoporosis.

Lisa Lorenzen, a liaison to the biotech industry at Iowa State University, said most Americans haven't worried about GM foods because they trust the regulatory system. She said many Europeans oppose GM foods because they don't trust governments that wrongly insisted for years that the beef supply, tainted by mad cow disease, was safe.

Opponents say genetically modified foods could cause allergic or toxic reactions and harm the environment. Worries include the mixing of GM crops with regular ones either by handlers, or pollen — already documented — and GM foods being sold where they're not approved.

On Tuesday, a Swiss biotech company said it mistakenly sold U.S. farmers an experimental, unapproved GM corn seed, and tons of the resulting corn was sold between 2001 and 2004. U.S. government agencies say there was no health or environmental risk.

In 2000, recalls, lawsuits and public uproar followed disclosure that StarLink GM corn, approved only for animal use, had gotten into taco shells and chips.

University plant scientists, industry, the Food and Drug Administration and numerous European science agencies say GM foods are safe.

"Nobody's been able to prove that anyone's even gotten the sniffles from biotechnology," Childs said.

Comment on this story

But Margaret Mellon of the Union of Concerned Scientists, said there's no system to track health problems caused by GM foods.

Her group, along with the Center for Science in the Public Interest, has long pushed for labeling — only required when GM products have properties different from ordinary foods, such as a higher nutrient content. They contend consumers deserve a choice if they want to avoid GM foods and they also want government regulation.

Currently, companies developing GM foods voluntarily send their data to the FDA, but there's no official approval before products go on sale.

"It's left up to the good nature of Monsanto or DuPont or other companies to do the right thing," said Gregory Jaffe, director of the biotechnology project at CSPI.