If you want to avoid sugar, aspartame, trans-fats, MSG, or just about anything else, you read the label. If you want to avoid G.M.O.'s - genetically modified organisms - you're out of luck. They're not listed. You could, until now, simply buy organic foods, which by law can't contain more than 5 percent G.M.O.'s. Now, however, even that may not work. The U.S. Department of Agriculture has approved three new kinds of genetically engineered (G.E.) foods: alfalfa (which becomes hay), a type of corn grown to produce ethanol), and sugar beets. And super-fast-growing salmon - the first genetically modified animal to be sold in the U.S., but probably not the last - may not be far behind. It's unlikely that these products' potential benefits could possibly outweigh their potential for harm. But even more unbelievable is that the Food and Drug Administration and the U.S.D.A. will not require any of these products, or foods containing them, to be labeled as genetically engineered, because they don't want to suggest or imply" that these foods are "different." They are arguably different, but more important, people are leery of them. Nearly an entire continent - it's called Europe - is so wary that G.E. crops are barely grown there and there are strict bans on imports (that policy is in danger). Furthermore, most foods containing more than 0.9 percent G.M.O.'s must be labeled.