Whole Foods Market, the grocery chain, on Friday became the first retailer in the United States to require labeling of all genetically modified foods sold in its stores, a move that some experts said could radically alter the food industry.

A. C. Gallo, president of Whole Foods, said the new labeling requirement, to be in place within five years, came in response to consumer demand. “We’ve seen how our customers have responded to the products we do have labeled,” Mr. Gallo said. “Some of our manufacturers say they’ve seen a 15 percent increase in sales of products they have labeled.”

Genetically modified ingredients are deeply embedded in the global food supply, having proliferated since the 1990s. Most of the corn and soybeans grown in the United States, for example, have been genetically modified. The alterations make soybeans resistant to a herbicide used in weed control, and causes the corn to produce its own insecticide. Efforts are under way to produce a genetically altered apple that will spoil less quickly, as well as genetically altered salmon that will grow faster. The announcement ricocheted around the food industry and excited proponents of labeling. “Fantastic,” said Mark Kastel, co-director of the Cornucopia Institute, an organic advocacy group that favors labeling.

The Grocery Manufacturers Association, the trade group that represents major food companies and retailers, issued a statement opposing the move. “These labels could mislead consumers into believing that these food products are somehow different or present a special risk or a potential risk,” Louis Finkel, the organization’s executive director of government affairs, said in the statement.