When the Food and Drug Administration first attempted to impose tough new regulations on the makers of vitamin and mineral supplements 15 years ago, the proposal generated truckloads of angry letters to Congress.

Now, as the FDA considers new guidelines on nutritional supplements, the controversy between the vitamin industry and the government seems poised to begin all over again.

The dispute this time is over labeling -- in particular over a section of the regulations proposed by the FDA last summer governing what kind of health claims can be made on food package labels, product inserts and store displays.

While the proposed rules liberalize the claims some foods may be able to make, they may prevent vitamin makers from saying their products prevent disease and help keep people healthy. The FDA says the proposals prevent claims not borne out by scientific evidence; the vitamin industry says it is the victim of bias and that the FDA is overstepping its authority.

The proposals are broadly defined to affect all food manufacturers, for the first time granting them the freedom to outline on package labels the role their products play in reducing the risk of disease. For years, Kellogg Co.'s All-Bran cereal boxes have listed the role that fiber plays in reducing the risk of cancer, and a handful of other companies have followed suit. But by and large the FDA has frowned on specific disease-related claims on food labels.

The proposed guidelines would change that, but there's a catch. The $3 billion worth of vitamin and mineral pills sold in America every year, over which the FDA also has authority, were singled out for special consideration.

The FDA long has been skeptical of vitamin makers' claims that their dietary supplements are necessary for general nutrition and to help prevent certain diseases, and a few terse paragraphs in the proposals made it clear that the nutritional supplement industry would have a tough time getting health claims past the new guidelines.

The industry calls that stand illegal, and said so in statements filed with the FDA last month.

The exchange has at times been heated and complicated, touching on issues that some say are central to the economic future of the vitamin business, and it's drawing the attention of consumer activists and medical associations that for years have battled the industry over the importance of extra vitamins and minerals to most Americans.

The final version of the FDA regulations is expected as early as this summer, but few experts expect the flurry of claims and counterclaims to be resolved anywhere but in court.

The feud between the FDA and the nutritional supplement industry began in the 1960s, when the agency began to pay close attention to what was then the new and rapidly growing health food business. In the early 1970s, citing evidence that nutrients could be toxic in certain amounts, the agency proposed that vitamin and mineral supplements not be sold in excess of certain predetermined "recommended" dosage levels.

The health food industry was outraged, and organized a massive letter-writing campaign that resulted in what became known as the Rogers-Proxmire Amendment of 1976, which effectively exempted the supplement industry from similar FDA attempts at regulation.

"Rogers-Proxmire meant the survival of our industry," said J.B. Cordaro, president of the Council for Responsible Nutrition, the vitamin industry's trade association. "Without that, the FDA ... could have crippled us."

The amendment, though, led to a rift between the FDA and the industry that has never healed.

Then-FDA commissioner Alexander Schmidt called the amendment a "charlatan's dream," and on several occasions in the 12 years since the amendment, FDA officials have publicly expressed reservations about the dangers of an unregulated supplement industry.

"They don't like that law at the FDA," said Stephen McNamara, a lawyer for the supplement industry with Hyman, Phelps & McNamara in Washington. "They don't want to talk about it and they do their best not to think about it."

Indeed, federal nutrition policy since the Rogers-Proxmire Amendment was passed has continued to express skepticism about the worth of nutritional supplements. The 1985 Dietary Guidelines for Americans, issued jointly by the Department of Health and Human Services and the Agriculture Department, state flatly that "there are no known advantages and some potential harm in consuming excessive amounts of any nutrient."

The government's guidelines also dismiss the broad nutritional claims for supplements made by pill makers, a position backed by the American Dietetic Association, the American Institute of Nutrition, the American Society for Clinical Nutrition and the American Medical Association. The latter, in a report published last spring, stated that "healthy adult men and healthy adult nonpregnant, nonlactating women consuming a usual varied diet do not need vitamin supplements."

But the Rogers-Proxmire Amendment has made it all but impossible for the FDA to act on any of its reservations about nutritional supplements, or to apply the same rigorous standards of safety and efficacy to vitamins that it does to drugs.

To some observers, the FDA's frustration over Rogers-Proxmire has a lot to do with the way vitamin makers were singled out in recent proposals covering health messages that can be carried on food products. The agency's move may be limited to the area of food labeling, but according to supplement industry lawyers it is nonetheless significant. "They're trying to put the lid back on," said one lawyer.

FDA officials dismiss the charges. "I'm not surprised by them," said Alan Forbes, director of the agency's office of nutrition and food sciences. The Council for Responsible Nutrition, he said, "is a trade association and they've got a job to do. But {the guidelines} are simply a reflection of the general thought process of the nutrition guidelines and the nation at large. They're simply a reflection of government policy."

Under the proposals, the FDA has suggested allowing health claims on labels as long as the information presented is truthful and not misleading to the consumer and reflects "the weight of scientific evidence."

In the preamble to the proposals, however, which serves as the advisory opinion for future interpretation, the FDA details the government's longstanding objections to mineral and vitamin supplements and concludes that "it may be more difficult for dietary supplements to meet the criteria" than food products.

FDA officials say they are within their rights to make that kind of regulatory judgment. The Council for Responsible Nutrition, however, says that under Rogers-Proxmire the FDA conclusion is illegal.

"They're turning the law on its head," said McNamara, who said the amendment explicitly states that dietary supplements have the right to make health-related claims on their labels.

Unless the FDA changes that part of the language between now and the time the final regulations are issued, Cordaro said, "It's going to come down to some kind of legal challenge."

For Cordaro and his industry, the issue is more than symbolic. Although it rocketed from a $500 million business in 1971 to $2 billion in annual sales a decade later, the supplement industry has been in a sales slump in recent years, with growth of just 2 percent last year and no growth the year before.

"The problem is that we've taken a lot of negative shots," Cordaro said. Confronting the FDA is just one step of many that Cordaro says his organization has to take to reverse what he calls the pervasive antisupplement bias.

The Council for Responsible Nutrition concedes the nutritional value of a balanced diet, but it stresses that studies show that many Americans simply do not eat that well.

The council also claims to have science on its side. Cordaro calls his opponents "traditional nutritionalists;" studies to be released soon, he said, will bear out the nutritional importance of supplements in preventing disease.

Cordaro said that the scientific community should be more tolerant toward newer, perhaps dissenting, scientific evidence, and that the FDA should relax its requirement that health claims be supported by a broad medical consensus.

"Consensus should not be viewed as some kind of holy grail which we should seek with unflagging devotion," Cordaro said in a speech three years ago. "Rather ... consensus is more like the Cheshire cat, appearing and disappearing unpredictably."