from about.com

Definition: According to the Dietary Supplement Health and Education Act, a dietary supplement is a product (other than tobacco) that:

- is intended to supplement the diet
- contains one or more dietary ingredients (including vitamins; minerals; herbs or other botanicals; amino acids; - and other substances) or their constituents
- is intended to be taken by mouth as a pill, capsule, tablet, or liquid
- is labeled on the front panel as being a dietary supplement

A new dietary ingredient is a dietary ingredient that was not sold in the U.S in a dietary supplement before October 15, 1994.

Although dietary supplements are regulated by the FDA as foods, they are regulated differently from other foods and from drugs. Whether a product is classified as a dietary supplement, conventional food, or drug is based on its intended use. Most often, classification as a dietary supplement is determined by the information that the manufacturer provides on the product label or in accompanying literature, although many food and dietary supplement product labels do not include this information.

to be continued...