Joe Sparatta, a chef with two restaurants, Heritage and Southbound, in Richmond, Va., said he was especially concerned about the F.D.A.’s decision not to require labeling of the genetically engineered salmon because his customers were demanding more information about the food on his menus.

“Guests ask about everything,” Mr. Sparatta said. “Is there dairy in this? Is this fish wild or farmed? What are your animals eating? We try to source as much as we can locally, which helps us know more about the products we use, but we can’t get everything from around here.”

He said that customers had only recently begun to ask about whether things were genetically modified, but he expected to get the question more frequently. “With this now being debated in Congress, I think more people are hearing about it and starting to ask questions and want to know,” Mr. Sparatta said.

Consumers are increasingly looking for information about the presence of genetically modified ingredients in their foods, according to research by the Hartman Group. “The G.M.O. issue is something that continues to be brought up in an unprompted way in our interviews with consumers,” said Laurie Demeritt, chief executive of Hartman. “And when we look at things like fat, sodium and sugar, G.M.O. is showing the strongest growth rate in terms of a characteristic that consumers are trying to avoid.”

In research Hartman did for a report on perceptions about genetically modified foods, about 58 percent of consumers were looking for “non-G.M.O.” food.

“It’s connected to this idea that a product is processed,” Ms. Demeritt said. “Consumers have a vision in their minds of people in lab coats taking syringes and injecting things into a product, a vision of food made in a lab — and that’s even worse in their minds than food coming off a factory line.”

She added that consumers did not necessarily understand what genetic engineering is, or even which crops are genetically engineered. “While it’s difficult for some people in the food space to hear because they want to educate consumers and talk to them about it, in most cases, consumers don’t really want to hear a long explanation about the science behind it,” she said.