Whole Foods Market, the grocery chain, announced on Friday that it would require all foods sold in its stores that contain genetically modified ingredients to be labeled as such within five years.

The company is the first retailer in the country to require the labeling, and its executives received a standing ovation when they made the announcement at the Natural Products Expo West, a trade conference being held this week in Anaheim, Calif. The show closes on Sunday.

A.C. Gallo, president of Whole Foods, said the move came in response to consumer demand.

Labels now used on Whole Foods products disclose when a product has been verified as free of genetically engineered ingredients by the Non-GMO Project, a nonprofit certification organization.

“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” as certified by the group.

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 more labeling.

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