The rules may be different in other countries but in Australia vitamin and supplement products fall under the brief of the Therapeutic Goods Administration, which is similar to the FDA. The TGA is part of the Federal Department of Health and also monitors prescription medications.

Generally, a seller of a vitamin or supplement product must provide the TGA with evidence that it contains the contents claimed for it. Advertising of these products can not be deceptive or misleading. For example, an advertisement for vitamins must not imply that vitamin supplements are a substitute for good nutrition or a balanced diet.

The TGA strongly advises people not to use the Net to import vitamin or supplement products unless they know exactly what is in the preparation and have checked the legal requirements for importation and use in Australia.

Anybody can lodge a complaint with the TGA about a vitamin or supplement product which may not meet the guidelines.

I think that this system works fairly well.