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What Are Dietary Supplements?

The term "dietary supplement" refers to a wide range of products including vitamins and minerals, herbs and other botanicals, amino acids, enzymes, and more. You can find dietary supplements in many forms, such as pills, gummies, powders, liquids, teas, and bars.

Some examples of common supplements include ashwagandha, berberine, quercetin, fenugreek, colloidal silver, mangosteen and L theanine. It's very important to talk to your doctor about taking any supplements and what side effects they might have.

Unlike medicines (drugs), dietary supplements are not intended to treat, diagnose, prevent, or cure diseases.


How are dietary substances supplements different from medicines?

Dietary supplements don't have the same strict safety and effectiveness requirements that medicines do. In the United States, all the medicines you can buy, even without a prescription, must be proven safe and effective, but dietary supplements do not have to be.

All prescription and non-prescription medicines are regulated in the US by the Food and Drug Administration (FDA). But dietary supplements are treated more like special foods.

In general, the FDA considers new medicines to be unsafe until they are proven safe in clinical trials. New medicines must go through a lot of testing to prove that they are safe and effective before being approved for use by the FDA. And the FDA must approve any new medicine before it can be legally sold in the US.

On the other hand, a dietary supplement can be sold without having to prove it is safe and effective first, as long as the maker doesn't claim it can treat, diagnose, prevent, or cure a disease (in which case the FDA would consider it to be a drug).

Supplements cannot contain anything that poses a known risk of illness or injury when used as directed on the label, or with normal use if there are no directions on the label. The FDA can stop a company from selling a supplement if it has been found to be unsafe, but only after the FDA gets reports that the supplement has caused harm.

Regulations for dietary supplements

Although supplements are not required to go through clinical trials, companies that make them are supposed to:

  • Have data showing the products are safe
  • Make sure that the details on product labels are truthful
  • Avoid making false claims
  • Correctly show what is in the supplement

Companies that make dietary supplements must also follow Good Manufacturing Practices (GMPs). The GMPs state that dietary supplements must:

  • Be produced in a quality manner
  • Not contain any contaminants or impurities
  • Be labeled with the ingredients that are actually in the product

The FDA watches for reports of illness, injury, or reactions to supplements. All supplement makers are supposed to report harmful effects to the FDA. The FDA also wants consumers to report reactions or other problems with supplements.

The FDA also watches for products on the market that make false claims or contain ingredients known to not be safe. The federal government can act against companies that make false claims about their products or if the supplements are found to be unsafe.

The American Cancer Society medical and editorial content team

Our team is made up of doctors and oncology certified nurses with deep knowledge of cancer care as well as editors and translators with extensive experience in medical writing.

Supplement Your Knowledge: Dietary Supplement Education Initiative

This site includes fact sheets and videos about dietary supplements for the public, educators and healthcare professionals. Materials for the public are available in English and Spanish.

Food and Drug Administration. Dietary Supplements. Last updated 8/16/2019. Accessed at on May 12, 2021.

Harvie M. Nutritional supplements and cancer: Potential benefits and proven harms. Am Soc Clin Oncol Educ Book. 2014:e478-86. 

National Center for Complementary and Integrative Health. Dietary and Herbal Supplements. Last updated February 2020. Accessed at on May 27, 2021.

Office of Dietary Supplements, National Institutes of Health. What You Need to Know: Dietary Supplements. Accessed at on May 11, 2021.

Last Revised: September 2, 2021

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