With consumer advocates, environmentalists and organic agriculturists occasionally heckling from the audience and staging street-theater demonstrations outside, the Food and Drug Administration today grappled with the controversial issue of how best to regulate genetically engineered food.

In the first of a series of public hearings aimed at engaging the public in discussions about federal policy on gene-altered foods, the agency's top officials heard that "shooting genes into chromosomes" is, depending upon the viewpoint of the speaker, either dangerous, unnatural and anti-religious, or a key to solving future worldwide food shortages and a boon to developing safer, more healthful and tastier foods.

After eight hours of testimony by nearly 100 speakers and several long debates by two panels of experts, there appeared to be little middle ground, which FDA Commissioner Jane E. Henney may have anticipated when she said at the outset of the meeting, "The FDA is here to listen. . . . Our goal is not to reach a conclusion at the end of the day."

From the beginning, the hearing was highly structured and tightly controlled in an apparent effort to avoid a donnybrook over the increasingly contentious use of bioengineering in the production of food.

Most of the daylong session was devoted to discussions by panels that appeared weighted with members who favor the FDA's current policy. That policy lets food producers voluntarily consult with the agency before marketing their genetically modified products and requires special labeling only when a food's nutritive value has been significantly altered or when consumers need to be informed about a safety issue.

The format, coupled with a two-minute time limit on public testimony and space restrictions in a conference room here that forced about 200 prospective speakers to watch the discussion on closed-circuit television in a nearby hotel ballroom without an opportunity to testify, led to complaints that the FDA had sidestepped a full and open debate.

"This meeting has excluded most of the public," complained one speaker, Max Gomberg, a University of Chicago student. Another student, Christine Phillips of DePaul University, said, "This format lends itself to sound bites."

Outside, in a broad plaza ringed by federal buildings in Chicago's downtown Loop, members of Greenpeace and several other environmental and consumer groups paraded with signs declaring "Genetically engineered food is poison." They also staged skits in which children costumed as Monarch butterflies fled in mock terror from a figure dressed as a huge gene-altered ear of corn and a protester portraying a biotechnology farmer injecting hormones into a papier-mache cow.

But for the most part, the hearing was conducted in a calm, businesslike manner, with FDA officials unswervingly defending their bioengineering policies as "well grounded in science" and panelists politely offering suggestions for changes.

"We believe our oversight is substantive, credible and appropriate," Henney told the meeting, while assuring critics that "it is our goal to have our review and regulatory process be as open as possible."

James Maryanski, biotechnology coordinator of the FDA's Center for Food Safety and Applied Nutrition, told the audience that food producers typically consult with the agency for one to two years before introducing a genetically engineered crop into the market. "If the food is not safe, the agency has broad authority to remove it from the market," he said.

Maryanski said most elements introduced into altered-food products are genes that produce enzymes and are unquestionably safe. He acknowledged that "unexpected adverse effects" are possible with the use of proteins in genetic modification processes and that the proteins would require testing to ensure that they do not contain toxins and allergens. However, he said he is confident that the voluntary consultation process would weed out unsafe products.

One of the panelists, Charles Margulis, representing the Greenpeace genetic engineering campaign, countered that the FDA's presentation "sounds like promotional literature of the [food] industry" and that the FDA's record on the issue so far is "not confidence-inspiring."

Some of the speakers, including Michael Phillips, executive director for food and agriculture for the Biotechnology Industry Organization, argued against requiring any labeling of gene-altered foods that "suggests in any way that these products are unsafe," although Phillips said that disclosing in labels the introduction of nutrients or allergens would be appropriate.

Edward Groth III, director of technical policy and public service for Consumers Union, called labeling of all genetically engineered foods a "key to public trust." He said, "The cynicism and distrust generated by top-down, arrogant communication will breed more distrust."

Additional FDA public meetings on genetic engineering are set for Nov. 30 in Washington and Dec. 13 in Oakland, Calif.

CAPTION: Opponents of genetically engineered foods demonstrate in Chicago as the Food and Drug Administration holds a public hearing on the issue.

CAPTION: A protester dressed as a giant ear of corn joins demonstrators outside hearing site.