A dietary supplement, also known as food supplement or nutritional supplement, is a preparation intended to supply nutrients, such as vitamins, minerals, fatty acids or amino acids, that are missing or are not consumed in sufficient quantity in a person's diet. Some countries define dietary supplements as foods, while in others they are defined as drugs.

Supplements containing vitamins or dietary minerals are recognised by the Codex Alimentarius Commission, the United Nations' highest authority on food standards, as a category of food.

United States

In the United States, a dietary supplement is defined under the Dietary Supplement Health and Education Act of 1994 (DSHEA) as a product that is intended to supplement the diet and contains any of the following dietary ingredients:

• a vitamin
• a mineral
• an herb or other botanical (excluding tobacco)
• an amino acid
• a dietary substance for use by people to supplement the diet by increasing the total dietary intake, or
• a concentrate, metabolite, constituent, extract, or combination of any of the above

Furthermore, it must also conform to the following criteria:

• intended for ingestion in pill, capsule, tablet, powder or liquid form
• not represented for use as a conventional food or as the sole item of a meal or diet
• labeled as a "dietary supplement"

The hormones DHEA (a steroid), pregnenolone (also a steroid) and the pineal hormone melatonin are marketed as dietary supplements in the US.

Regulation

Pursuant to the DSHEA, the Food and Drug Administration (FDA) regulates dietary supplements as foods, and not as drugs. While pharmaceutical companies are required to prove the safety or effectiveness of their products, until recently supplement manufacturers were not, and the FDA could take action only after a dietary supplement had been proven harmful. However, new FDA rules will, by June 2010, ensure that all production of dietary supplements must comply with current good manufacturing practices, and be manufactured with "controls that result in a consistent product free of contamination, with accurate labeling." In addition, the industry is now required to report to the FDA "all serious dietary supplement related adverse events."

The DSHEA, passed in 1994, was the subject of lobbying efforts by the manufacturers of dietary supplements. At the time of its passage DSHEA received strong support from consumer grassroots organizations, and Members of Congress. In recognition of this, President Bill Clinton, on signing DSHEA into law, stated that "After several years of intense efforts, manufacturers, experts in nutrition, and legislators, acting in a conscientious alliance with consumers at the grassroots level, have moved successfully to bring common sense to the treatment of dietary supplements under regulation and law." He also noted that the passage of DSHEA "speaks to the diligence with which an unofficial army of nutritionally conscious people worked democratically to change the laws in an area deeply important to them" and that "In an era of greater consciousness among people about the impact of what they eat on how they live, indeed, how long they live, it is appropriate that we have finally reformed the way Government treats consumers and these supplements in a way that encourages good health."