What key aspect of dietary supplements differentiates them from prescription medications?

Dietary supplements are primarily regulated as foods rather than drugs under the Dietary Supplement Health and Education Act (DSHEA) of 1994. This regulation means that they do not undergo the same rigorous pre-market approval process as prescription medications. Unlike prescription drugs, which must provide evidence of safety and efficacy through clinical drug trials before they can be marketed to the public, dietary supplements are allowed to be sold without such proof.

Manufacturers of dietary supplements are responsible for ensuring that their products are safe and that any claims made on the packaging are truthful and not misleading, but they do not need to demonstrate efficacy in clinical trials prior to marketing. This is a fundamental difference that sets dietary supplements apart from prescription medications in terms of regulatory oversight and pre-market evaluation.

The other options highlight aspects that do not apply to dietary supplements in the same way they do to prescription medications. Dietary supplements are not classified as controlled substances, they do not have the same stringent requirements for closure of clinical trials, and while proper storage conditions are important, that is not unique to dietary supplements as medications also require specific storage conditions.