Four months after pledging to end the "Tower of Babel" in American grocery stores, Secretary of Health and Human Services Louis W. Sullivan yesterday proposed a set of uniform definitions that would clarify and standardize the labels on virtually every food product sold in the United States.

The 400-page proposal, which will be published next week in the Federal Register, updates and expands the list of what nutrients should and should not be listed on food labeling and defines precisely what is meant by previously confusing terms such as "cholesterol-free" and "reduced cholesterol" that manufacturers have used at their own whim.

Under the new rules:

"Cholesterol free" could be used only if a food product has less than 2 milligrams of cholesterol per serving and less than 5 grams of fat -- no more than 2 grams of which can be saturated fat.

"Low cholesterol" would mean less than 20 milligrams per serving.

"Reduced cholesterol" would apply only to food with 75 percent less cholesterol than the product on which it is based.

Officials of the Food and Drug Administration said that in the coming months they will follow with two more detailed proposals. The first will set precise standards for use of terms such as "high in fiber," "lite," and "fresh," and the second will set out guidelines for how food labels should be designed.

Final rules are expected to be in place by this fall and full industry compliance is expected a year later.

"American consumers should have full access to information that will help them make informed choices about the food they eat," said Sullivan, who first announced his department's intention to rewrite the regulations governing food labels last March. "The consumer should be able to read and understand food labels, based on reliable and vital information. These proposed regulations will help make food labels more clear and cogent."

The FDA's intention to replace the existing, largely voluntary, system of labeling established 17 years ago with updated, mandatory guidelines comes at a time of increasing consumer confusion over the nutritional content of food. At least two bills in Congress have been introduced to authorize the rewriting of labeling guidelines and industry and consumer groups have joined in pressing for reforms.

Yesterday's FDA proposals are very close to what Congress is considering and what some industry and consumer groups have endorsed.

The guidelines, for example, require that the amount of thiamin, riboflavin, and niacin be dropped from labels, and four new food components that currently are optional be made mandatory: saturated fat, calories from fat, cholesterol, and fiber.

"Thiamin, riboflavin, niacin are primarily connected with deficiency diseases that are virutally nonexistent in the U.S. public," said F. Edward Scarbrough, acting director of the FDA's Office of Nutrition and Food Sciences. "We would much rather concentrate on nutrients associated with chronic diseases."

The proposals also create standardized serving sizes for 159 food categories. Under current rules, manufacturers can set whatever serving size they wish on food labels, which has led to what consumer groups have called misleading claims. For example, Sara Lee "lite" cheesecake is advertised as "only 200 calories per serving." But the only major difference between Sara Lee's low calorie cheesecake and regular cheesecake is that the serving size in the "lite" product is smaller.

"We want to make sure people can understand what they are getting," acting FDA Commissioner James Benson said.

While praising the general thrust of Sullivan's proposals, several consumer and industry groups said the new guidelines fall short in several key areas.

For example, some consumer groups said that the rules would not prevent food manufacturers from switching from health messages that were regulated by the FDA to ones that are not.

"The FDA could end up on a spinning wheel," said Bruce Silverglade of the Center for Science in the Public Interest. "As soon as it defines one set of terms like high fiber, food companies may come up with something like fiber rich and evade the agency's official designation."

By contrast, a food labeling bill sponsored by Rep. Henry A. Waxman (D-Calif.) and Sen. Howard M. Metzenbaum (D-Ohio) would prohibit the use of any undefined terms on a food label without FDA approval.

Further, the guidelines also leave unresolved the politically sensitive issue of whether federal food label rules would preempt any states from adopting their own stricter or more lenient rules on the same subject.

Many industry groups have pressed for such a provision, saying that without it the goal of a consistent and understandable national food label policy would be frustrated. The congressional food labeling bills have endorsed the idea of federal preemption.

But Sullivan said the administration had not yet decided whether the federal rules would preempt states in food labeling. Both the Office of Management and Budget and senior White House officials apparently oppose the idea.

Cholesterol Free: Less than 2mg of cholesterol per serving. Less than 5 grams of fat, of which less than 2 grams may be saturated fat.

Low Choleterol: Less than 20 mg of cholesterol per serving. Less than 5 grams of fat, of which less than 2 grams may be saturated fat.

Reduced Cholesterol: 75% or less cholesterol than the original product.