"We've been asking for this for a long time," said Loren Israelsen, executive director of the Utah Natural Products Alliance, of the 850-page rule. "This regulation clearly unifies the industry under a single federal standard, deals internationally with building symmetry into the supply chain and manufacturing process, and harmonizes the methods and documents used in trade and commerce."

The rule has been evolving since 1994, when Congress limited the FDA's oversight of vitamins and other dietary supplements. It is designed to address concerns that existing federal regulations allowed supplements onto the market that were contaminated or didn't contain the dietary ingredients claimed on the label.

''The final rule will help ensure that dietary supplements are manufactured with controls that result in a consistent product free of contamination, with accurate labeling,'' said Robert E. Brackett, director of the FDA's Center for Food Safety and Applied Nutrition. It will be phased in over three years, starting in August.

Israelsen said the public deserves to have confidence in the production and labeling processes, adding that Utah's cluster of supplement and herbal-product manufacturers - such as Xango, Nutraceutical Corp., Nature's Sunshine and Weider Nutrition - are industry leaders in developing the best general manufacturing processes.

"Utah companies have invested heavily over the years to establish quality standards and practices that really are state of the art," he said. "Those companies don't expect to see many changes in the way they do daily business because of this rule."

Added Bob Freeze, vice president of public relations at Lehi-based XanGo LLC: "We believe this sends a strong message to Congress and to American consumers that the majority of natural-products companies are responsible and welcome this kind of accountability."

Last year, the FDA found that some supplements contained undeclared active ingredients used in prescription drugs for erectile dysfunction. In the past, regulators found supplements that didn't contain claimed levels of vitamins C or A.

If, upon inspection, the FDA finds that supplements do not contain ingredients they claim to contain, the agency would consider the products adulterated or misbranded. In minor cases, the agency could ask the manufacturer to remove the ingredient or revise its label. In more serious cases, it could seize the product, file a lawsuit or even seek criminal charges.

Israelsen said he will be interested to see whether the FDA actually can enforce the rule, calling it a "resource-constrained agency."

"Hopefully, this will mean an increase in FDA inspections of manufacturing facilities," he said. "We're in the odd position of saying 'We would like to see more of you [inspectors] more often.' ''

Dietary supplements - pills, liquids or other products people take to improve their diets - are a $22 billion industry.

Most companies already test their raw ingredients once they come into the plant, said Steve Mister, president and CEO for the Council for Responsible Nutrition, a trade association representing about 65 manufacturers.

''This raises the bar so that all have to comply,'' Mister said.

The new rule goes into effect Aug. 24. It will have a three-year phase-in to give smaller manufacturers more time to comply, but even large manufacturers won't have to comply until June 2008.

The rule applies to all domestic and foreign companies that manufacture, package and label supplements for sale in the U.S. It requires them to analyze the identity, purity and strength of all the ingredients that go into their products before they are distributed. It also includes requirements for record keeping and handling consumer complaints.

Israelsen hopes the expansive rule recognizes the burden placed on small manufacturers, contending that few can afford to develop an in-house testing facility or to contract with an outside laboratory.

He also said the existence of a federal regulation makes it easier for domestic manufacturers to demand higher-quality products from their foreign suppliers. "That's always helpful," he said. "It brings the imprimatur of federal authority."

Sidney Wolfe, who has testified before Congress on problems with dietary supplements, said the new rule does not ease his concern that unsafe supplements are too easy to bring to market.

''You still don't have to show the product is safe. You don't have to prove it works,'' said Wolfe, director of Public Citizens Health Research Group.

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* THE ASSOCIATED PRESS contributed to this report.