Medical Health Encyclopedia

Vitamins - Introduction

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Food and supplement labels now typically list the Daily Value (DV). This is the percentage of the amount of a nutrient that experts believe people need in their daily diet. On food labels it is usually based on one serving size for a person who takes in 2,000 calories a day.

Regulating Quality

Regulation of dietary supplements by the U.S. Food and Drug Administration (FDA) is a complex issue.

Labels on vitamins and other dietary supplements now include nutrient information and list all ingredients, including identifying parts of plants from which ingredients may be taken. Unlike the labels for drugs, however, labels for vitamins and supplements may not claim to prevent or treat any specific disease. Labels for vitamins and supplements include one of the following:




  • Health claim -- description of how the substance may reduce the risk of a health-related condition
  • Nutrient claim -- description of the amount of the nutrient in the product
  • Structure or function claim -- description of how the product may affect organs or systems of the body, without claiming to prevent or treat specific diseases

The quality of dietary supplements depends on the manufacturer and is not regulated by the FDA. The U.S. government does not require that supplements be standardized, meaning that the amounts or quality of nutrients may vary depending on the batch. So, more expensive supplements are not necessarily better than less expensive ones. Government regulations are in the process of catching up to the boom in the supplement industry. In the meantime, some companies voluntarily adhere to rigorous quality controls, while others do not.

The U.S. Pharmacopeia (USP), an independent organization that sets quality standards for drugs, has also implemented standards for vitamins. Consumers may look for the USP label on products of companies that adhere to these standards. USP verification means the following:

  • What is in the bottle matches what is listed on the label.
  • There are no harmful levels of contaminants.
  • The supplement will be absorbed properly into the body.
  • It has been produced according to good manufacturing standards.
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