The U.S. Food and Drug Administration has banned the sale of this popular dietary supplement for lowering cholesterol, saying the substance contains a powerful prescription drug.

The action – the first of its kind by the agency – goes to the heart of a long-running debate over the boundary between drugs and dietary supplements, which get far less regulatory scrutiny and have become increasingly popular in recent years.

The maker of Cholestin, Pharmanex Inc. of Simi Valley, Calif., advertised that the product lets users “lower your cholesterol without drugs” because it is derived from an extract of Chinese red rice yeast.

But Cholestin contains lovastatin, a prescription drug sold under the brand name Mevacor by pharmaceutical giant Merck & Co., the FDA said. FDA regulations prohibit supplement makers from marketing products that are already on the market as drugs.

The FDA said that Pharmanex was marketing lovastatin and that it was therefore not a dietary supplement and could not be sold. Lovastatin is one of a class of drugs that increase the removal from the body of low-density lipoprotein (LDL) cholesterol, the type most strongly implicated in causing blood vessel blockages, and reduce the production of LDL by interfering with the liver’s cholesterol synthesis.

Pharmanex offers Cholestin for people whose cholesterol levels are elevated but
below the 240 milligrams per deciliter mark that is considered dangerously high. By doing so, the company can avoid charges that it is offering to cure disease,
which also would violate FDA rules.