This New Yorker article by Michael Specter discusses the supplement industry, relevant legislation, including the 1994 DSHEA act, and provides some interesting historical context. Although this article is about supplements intended for human use, many well-meaning pet owners purchase and administer human supplements to their pets.
and (bold added for emphasis)The diet-pill business may be the most visible segment of the vitamin-, mineral-, and herbal-supplement industry, but it is by no means the largest. Thousands of different tablets, elixirs, potions, and pills are sold in the United States, and remarkably little is known about most of them. That doesn’t deter consumers. Since 1994, when Congress passed a law that deregulated the supplement industry and opened it to a flood of new products, the use of largely unproved herbal remedies—from blueberry extract for impaired vision to saw palmetto for the treatment of enlarged prostates and echinacea to prevent colds—has increased as rapidly as the use of any commonly prescribed drug.
Since that legislation, the Dietary Supplement Health and Education Act, became law, companies have been able to say nearly anything they want about the potential health benefits of what they sell. As long as they don’t blatantly lie or claim to have a cure for a specific disease, such as cancer, diabetes, oraids, they can assert—without providing evidence—that a product is designed to support a healthy heart (CardiAll, for example), protect cells from damage (Liverite), or improve the function of a compromised immune system (Resist). There are almost no standards that regulate how the pills are made, and they receive almost no scrutiny once they are, so consumers never truly know what they are getting. Companies are not required to prove that products are effective, or even safe, before they are put on the market.
Still, there is more to the growing reliance on supplements than the lapses of a single law: Americans long ago wearied of taking doctors’ orders, and, increasingly, they are skeptical about the motives of big pharmaceutical companies. People want to feel in control of their own health. Supplements, with their “natural” connotations and cultivated image of self-reliance, let them do that
One recent Harris poll found that most people believe that if a supplement is on the market it must have been approved by some government agency (not true); that manufacturers are prohibited from making claims for their products unless they have provided data to back those claims up (no such laws exist); and that companies are required to include warnings about potential risks and side effects (they aren’t). “When something goes wrong, though, most people expect government health officials to find a solution,” David A. Kessler told me. Kessler, who is the dean of the School of Medicine at the University of California at San Francisco, was the F.D.A. commissioner when Congress passed the Dietary Supplement Act, which he adamantly opposed. “This is really the classic American ambivalence, and it has always been part of our nature,” he said.