In the United States, a dietary supplement is defined under the Dietary Supplement Health and Education Act of 1994 as a product taken by the mouth that contains a dietary ingredient that is intended as a supplement to the diet. By virtue of the act, this dietary ingredient could be one or any combination of the following:
a dietary substance for use by man to supplement the diet by increasing the total dietary intake (e.g., enzymes or tissuess from organss or glands),
a concentrate, such as a meal replacement or energy bar or
a metabolite, constituent or extract.
Dietary supplements are not regulated in the same manner as drugs. The FDA does not have primary responsibility over their safety. Instead, that role falls to the manufacturer of the supplement itself.
Now, compounds sold under the dietary supplement law cannot make claims about being able to cure diseases. As the FDA states it:
No, a product sold as a dietary supplement and promoted on its label or in labeling* as a treatment, prevention or cure for a specific disease or condition would be considered an unapproved--and thus illegal--drug. To maintain the product's status as a dietary supplement, the label and labeling must be consistent with the provisions in the Dietary Supplement Health and Education Act (DSHEA) of 1994.
