You can't see it, taste it or smell it. It's not listed on the label. But there's a good chance that if you eat something containing milk, corn, soybeans or potatoes you've got one of the century's most controversial food additives on your plate. DNA.It could cause toxic effects, allergic reactions, antibiotic resistance and one great big risk to the environment. Maybe.Genetically engineered (GE) food comes from plants which have had their DNA structures artificially altered, or from cows which have been dosed with genetically altered hormones. The changes are similar to those found in hybrid plant varieties. But instead of cross-breeding plants, scientists insert genes from completely different plants -- or animals -- to make a new variety of seed with specific characteristics, such as resistance to herbicides or pests. They also insert genetic markers (usually an antibiotic resistance trait) so biotech companies -- which patent the plants -- can identify them as their own. At the heart of the controversy over GE food is the fact that even though it's already growing on 45 million acres of American farmland, nobody really knows what those crops might do -- to other crops, the environment, or consumers.One of the most infamous examples of GE food was the Flavr Savr tomato, which came and went from the American market in early 1996. It used flounder genes to make the tomato last longer in shipping. However, it didn't win any prizes for its great taste, and many vegetarians refused to eat it because of its animal content.The Flavr Savr is unique in that it was one of the few GE foods advertised as such. Most of the GE foods we eat aren't even labeled, a condition which some groups around the world are working to change. Britain's Prince Charles has stated he will not serve or eat GE foods. Austria has banned these "Frankenfoods," and other countries in Europe are following suit.In the United States, consumers are kept in the dark, as the Food and Drug Administration doesn't consider DNA to be an ingredient, and so doesn't require that GE foods be labeled. The agribusinesses developing them keep experimenting, and we munch away like hungry guinea pigs.In 1996, the Little Marais, Minnesota-based Pure Food Campaign (now the Campaign for Food Safety) called for a boycott of products containing corn and soy which might have been genetically altered, including Nestle Crunch, Similac infant formula, Kraft salad dressings, Fritos corn chips and Coca-Cola.Last May, the Campaign for Food Safety sued the FDA demanding that all genetically engineered foods be labeled, or taken off the market.The argument, explains Ronnie Cummins, national director, is that since the Food, Drug and Cosmetic act of 1958 requires all material changes to food to be labeled, GE food must also be labeled. According to a 1997 survey, that's what 90 percent of Americans want. But biotech companies worry that consumers would avoid GE food if it were labled."They know consumers are not going to buy something they can't trust," says Cummins.One of the biggest concerns with GE food is that it hasn't been around long enough for its potential impact to be known.Allison A. Snow, assistant professor of biology at the University of Ohio in Columbus, wrote a report for the Environmental Protection Agency on the risks associated with genetically engineered crops."We don't know how new traits, such as resistance to insecticides or resistance to herbicides, will come up when they migrate," says Snow, explaining that GE plants can cross-pollinate with other plants and pass along their GE traits. The result could be positive, but it could also be disastrous. At the Rural Advancement Foundation International, executive director Pat Mooney works on determining what the effect of GE crops could be. "We're not automatically opposed to biotechnology or genetically modified organisms," says Mooney from the not-for-profit foundation's Winnipeg, Canada, head office. "But we should be very careful ... it takes at least a generation before the impact can even begin to be seen," he adds. "It may be fine, but with something experimental like this, unless we're absolutely certain it can't be a risk to the environment or our health, it shouldn't be introduced unless it addresses some greater human need."As far as Mooney is concerned, the only needs GE foods meet are those of big agribusiness. For one thing, GE crops increase farmers' reliance on seed and pesticide companies. Twenty years ago, there were about 7,000 seed companies, but now, a third of the global seed market is controlled by just 10 companies. Of these, the St. Louis-based Monsanto is among the top five.One of Monsanto's products is the Roundup Ready soybean, which has been genetically engineered to resist the herbicide Roundup, also manufactured by Monsanto. Farmers can kill weeds with the herbicide, and not have their crops suffer. The problem is, these seeds are patented, which means that farmers who do as farmers have always done -- save seeds from one crop to plant the next year -- violate Monsanto's copyright. They have to either buy a new set of seeds each year, or, as some farmers have already done, face serious fines and copyright infringement lawsuits. So much for nature. Perhaps bioengineered crops will increase farmers' yields, which will make up for the licensing fee they have to pay to seed companies. But what happens when farmers become dependent on these crops? "We don't know what will happen to the price once the market is established," says Mooney.Agribusiness companies put marker genes in their GE plants so they can tell if a farmer has "pirated" a crop. In the name of copyright protection, Delta and Pine, a Monsanto subsidiary, developed a genetic trait called the Terminator. It will render seeds from GE plants sterile and thus useless for replanting."It's the worst patent we've come across, and we've come across some pretty bad ones," says Mooney."It jeopardizes food security for 1.4 billion people," Mooney says. Terminator's target market is the Third World, where agribusinesses argue it's necessary. Without it, farmers could "pirate" GE technology by saving seeds to grow in following years.So far, the Terminator gene has only been used in cotton and tobacco, but its developers suggest it can work on any plant species, and soon hope to apply it to soy beans, wheat and rice.The trouble is, no one really knows whether those plants might cross-pollinate with other related species. The chance that the sterility gene could make it into other plants is enough to make environmentalists and others concerned about the world's future food supply cringe. At a meeting in Washington last month of the Consultative Group on International Agricultural Research, 8,000 scientists voiced disapproval of the Terminator technology because they weren't convinced it was safe.Even so, it is believed that more than half of the soy, corn and cotton grown in the United States will be genetically engineered by the year 2000. For that reason, Cummins suggests consumers voice their opposition before it's too late."This is a watershed decision," he says. "If we go down the path of genetically engineered food and fiber, this could be the thing that pushes the global economy and the global ecosystem over the edge."