He also expressed his frustration at the fact that the F.D.A. has spent years debating a policy that would encourage manufacturers to inform the agency of new dietary ingredients, but has not yet published it.

Dr. Gottlieb stated that the F.D.A. create an online watch list of specific ingredients of concern to the agency.

The supervision of F.D.A. is based on a 1994 federal law that imposed minimum reporting and labeling requirements on vitamin, mineral and medicinal plant manufacturers – a nascent industry at the time. To prevent a company from selling a product, the law requires that the F.D.A. to prove that it is dangerous. The agency says that it is difficult to track the myriad of products, many of which are sold over the Internet.

The law also obliges companies to inform the F.D.A. they make a dietary supplement, but do not say what it contains.

"It simply makes it impossible for the agency to control the market," said Dr. Lurie.

The 25-year-old law is gaining more and more criticism as the industry grows. There are currently between 50,000 and 80,000 dietary supplements on the market, according to the F.D.A. The agency also indicates that three out of four American consumers now consume regularly a dietary supplement. For older Americans, the rate is four out of five.

In recent years, the F.D.A. has cracked down on several sectors of the industry, including dietary supplements sold for weight loss, sexual function and energy enhancement. More recently, one of the main objectives has been kratom, a botanical substance marketed as a safe alternative to opioids or to relieve the withdrawal symptoms of opioid users. The F.D.A. ordered that kratom imports be seized and ordered companies not to use it in supplements. The agency has linked several deaths to kratom.

Steve Mister, Executive Director of the Council for Responsible Nutrition, which represents the dietary supplement business, said he believes the dietary supplement business is "remarkably safe". He also said the current law strikes the right balance between ensuring safety and giving consumers access to affordable products.

"These products are not drugs and should not be regulated as drugs," he said. Mr. Mister also stated that his group supported the measures taken by the FD.A. in the fight against fraud and worked with Congress to increase the program's budget.