27.3: Dietary Supplements

Like many Americans, you may take dietary supplements in an effort to stay healthy. With so many dietary supplements available and so many claims made about their health benefits, how can you decide whether a supplement is safe or useful? This fact sheet provides a general overview of dietary supplements, discusses safety considerations, and suggests sources for additional information.

Key Points

• Dietary supplements contain a variety of ingredients, such as vitamins, minerals, amino acids, and herbs or other botanicals. Research has confirmed health benefits of some dietary supplements but not others.
• To use dietary supplements safely, read and follow the label instructions, and recognize that “natural” does not always mean “safe.” Be aware that an herbal supplement may contain dozens of compounds and that all of its ingredients may not be known.
• Some dietary supplements may interact with medications or pose risks if you have medical problems or are going to have surgery. Most dietary supplements have not been tested in pregnant women, nursing mothers, or children.
• The U.S. Food and Drug Administration (FDA) regulates dietary supplements, but the regulations for dietary supplements are different and less strict than those for prescription or over-the-counter drugs.
• Tell all your health care providers about any complementary health approaches you use. Give them a full picture of what you do to manage your health. This will help ensure coordinated and safe care.

Federal Regulation of Dietary Supplements

The Federal Government regulates dietary supplements through the FDA. The regulations for dietary supplements are not the same as those for prescription or over-the-counter drugs.

• Manufacturers of dietary supplements are responsible for ensuring that their products are safe and that the label information is truthful and not misleading. However, a manufacturer of a dietary supplement does not have to provide the FDA with data that demonstrate the safety of the product before it is marketed.¹ In contrast, manufacturers of drugs have to provide the FDA with evidence that their products are both safe and effective before the drugs can be sold.
• Manufacturers may make three types of claims for their dietary supplements: health claims, structure/function claims, and nutrient content claims. Some of these claims describe the link between a food substance and a disease or health-related condition; the intended benefits of using the product; or the amount of a nutrient or dietary substance in a product. Different requirements apply to each type of claim. If a dietary supplement manufacturer makes a claim about a product’s effects, the manufacturer must have data to support the claim. Claims about how a supplement affects the structure or function of the body must be followed by the words “This statement has not been evaluated by the U.S. Food and Drug Administration (FDA). This product is not intended to diagnose, treat, cure, or prevent any disease.”
• Manufacturers must follow “current good manufacturing practices” for dietary supplements to ensure that these products are processed, labeled, and packaged consistently and meet quality standards.
• Once a dietary supplement is on the market, the FDA evaluates safety by doing research and keeping track of any side effects reported by consumers, health care providers, and supplement companies. If the FDA finds a product to be unsafe, it can take action against the manufacturer and/or distributor, and may issue a warning or require that the product be removed from the marketplace.

Sources of Science-Based Information

It’s important to look for reliable sources of information on dietary supplements so you can evaluate the claims that are made about them. The most reliable information on dietary supplements is based on the results of rigorous scientific testing.

To get reliable information on a particular dietary supplement:

• Ask your health care providers. Even if they don’t know about a specific dietary supplement, they may be able to access the latest medical guidance about its uses and risks.
• Look for scientific research findings on the dietary supplement. The National Center for Complementary and Integrative Health (NCCIH) and the National Institutes of Health (NIH) Office of Dietary Supplements (ODS), as well as other Federal agencies, have free publications, clearinghouses, and information on their Web sites.

Safety Considerations

If you’re thinking about or currently using a dietary supplement, here are some points to keep in mind.

• Tell all your health care providers about any complementary health approaches you use. Give them a full picture of what you do to manage your health. This will help ensure coordinated and safe care.
• It’s especially important to talk to your health care providers if you:
  • Take any medications (whether prescription or over-the-counter). Some dietary supplements have been found to interact with medications. For example, the herbal supplement St. John’s wort interacts with many medications, making them less effective.
  • Are thinking about replacing your regular medication with one or more dietary supplements.
  • Expect to have surgery. Certain dietary supplements may increase the risk of bleeding or affect the response to anesthesia.
  • Are pregnant, nursing a baby, attempting to become pregnant, or considering giving a child a dietary supplement. Most dietary supplements have not been tested in pregnant women, nursing mothers, or children.
  • Have any medical conditions. Some dietary supplements may harm you if you have particular medical conditions. For example, by taking supplements that contain iron, people with hemochromatosis, a hereditary disease in which too much iron accumulates in the body, could further increase their iron levels and therefore their risk of complications such as liver disease.
• If you’re taking a dietary supplement, follow the label instructions. Talk to your health care provider if you have any questions, particularly about the best dosage for you to take. If you experience any side effects that concern you, stop taking the dietary supplement, and contact your health care provider. You can report serious problems suspected with dietary supplements to the U.S. Food and Drug Administration and the National Institutes of Health through the Safety Reporting Portal.
• Keep in mind that although many dietary supplements (and some prescription drugs) come from natural sources, “natural” does not always mean “safe.” For example, the herbs comfrey and kava can cause serious harm to the liver. Also, a manufacturer’s use of the term “standardized” (or “verified” or “certified”) does not necessarily guarantee product quality or consistency.
• Be aware that an herbal supplement may contain dozens of compounds and that all of its ingredients may not be known. Researchers are studying many of these products in an effort to identify what ingredients may be active and understand their effects in the body. Also consider the possibility that what’s on the label may not be what’s in the bottle. Analyses of dietary supplements sometimes find differences between labeled and actual ingredients. For example:
  • An herbal supplement may not contain the correct plant species.
  • The amounts of the ingredients may be lower or higher than the label states. That means you may be taking less—or more—of the dietary supplement than you realize.
  • The dietary supplement may be contaminated with other herbs, pesticides, or metals, or even adulterated with unlabeled, illegal ingredients such as prescription drugs.

For current information from the Federal Government on the safety of particular dietary supplements, check the “Dietary Supplement Alerts and Safety Information” section of the FDA Web site or the “Alerts and Advisories” section of the NCCIH Web site.

Public domain content

• Dietary Supplements. Authored by: National Center for Complementary and Integrative Health. Provided by: National Institutes of Health. Located at: https://nccih.nih.gov/health/supplements/wiseuse.htm. License: Public Domain: No Known Copyright