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Choosing and Using Dietary Supplements Wisely

Understanding the claims on dietary supplement labels

Before you buy a dietary supplement, read the label carefully. Look at the claims, packaging, ingredients, and directions for use. It can be easy to misread the claims that are being made about products.

The makers of dietary supplements are allowed to make 3 kinds of claims on the labels of their products (or in their advertising):

  • Nutrient content claims: These are statements about the amount of a nutrient contained in a product. For example, the product label may state that a supplement is ‘high potency’ or ‘a good source’ of a nutrient, such as a vitamin.  
  • Health claims: These are statements about known health benefits of certain compounds. For example, claims such as “folate may reduce the chance of pregnant women delivering an infant with neural tube defects” fall into this category. The US Food and Drug Administration (FDA) must pre-approve all health claims and requires that they be supported by scientific studies.
  • Structure or function claims: These are claims about the effect of the dietary supplement on the structure or function of the body.

Structure or function claims

These are the most confusing claims. The following are structure or function claims that are considered OK for dietary supplements:

  • How the product works (“works as an antioxidant”)
  • How the product affects the body’s physiology (“promotes normal urinary flow”)
  • How the product might affect lab test results (“supports normal blood glucose”)
  • Claims of maintenance (“helps maintain a healthy circulatory system”)
  • Other non-disease claims (“helps you relax”)
  • Claims for common conditions and symptoms (“reduces irritability, bloating, and cramping associated with premenstrual syndrome”)

Structure or function claims are not reviewed by the FDA. In fact, labels with these types of claims must include the disclaimer “This statement has not been evaluated by the Food and Drug Administration. This product is not intended to diagnose, treat, cure, or prevent any disease.”

It’s easy to misunderstand structure or function claims. For example, many people believe that a statement like “helps maintain a healthy prostate gland” means the product has been proven to prevent or treat diseases like prostate cancer. This is not the case.

Don’t assume that because a product claims to support or promote healthy body function that it prevents or reduces the risk of any disease, including cancer.

Unlike the case with medicines, supplement makers cannot claim that their product can treat, diagnose, prevent, or cure diseases. For example, they can't say the supplement “reduces arthritic pain” or “treats heart disease.” Claims like these can only be made for medicines (drugs) that have been proven to do what they claim. Making such a claim automatically makes the product a drug, which would then be required to have the same proof of safety and effectiveness that the FDA requires for all drugs.

Seals of quality assurance

There are several organizations that provide quality testing and allow products to show a seal of quality assurance if they pass specific tests. This seal usually means that quality standards were used when making the product. They also test to be sure the ingredients listed on the label are actually in the product and that it doesn’t contain any contaminants or harmful chemicals.  

Examples of organizations that offer quality testing are*:

  • US Pharmacopeia
  • NSF International

*Inclusion on this list does not imply endorsement by the American Cancer Society.

Tips for choosing and using dietary supplements safely

  • Investigate before you buy or use. There are many resources in libraries and online. Look past the information that comes from the makers of the products, which can sometimes be biased or misleading. Find materials from reliable third parties, such as researchers or government agencies. (See the “Finding trustworthy information about dietary supplements” section for some places to start.)
  • Consider the name and reputation of the manufacturer or distributor. Dietary supplements made by nationally known food or drug manufacturers are more likely to be made using tight quality controls because these companies have a reputation to uphold.
  • Check with your doctor or other health care provider before you try a supplement. While your doctor might not know about all the products available, they may be able to tell you what isn’t safe.
  • Make sure that the label provides a way to contact the company if you have questions or concerns. Reputable manufacturers will give contact information on the label or packaging of their products.
  • Avoid products that claim to be “miracle cures,” “breakthroughs,” or “new discoveries.” Also avoid supplements that claim to have benefits but no side effects or are based on a “secret ingredient” or method. Such claims are almost always fraudulent, and the product may contain harmful substances, drugs, or contaminants.
  • Avoid products that claim to treat a wide variety of unrelated illnesses. If a supplement claims that it can diagnose, treat, cure, or prevent disease, such as “cures cancer,” or “stops tumor growth,” the product is being sold illegally as a drug.
  • Try to avoid mixtures of many different supplements. The more ingredients, the greater the chances of harmful effects. Mixtures also make it harder to know which substance is causing any side effects.
  • Start only one product at a time. Note any side effects you have while taking the product. If you have any side effects, stop taking the supplement. Report the side effects to your doctor, and be sure to report any serious ones to the FDA.
  • If you have any surgery or procedure planned, including dental surgery, talk with your surgeon about whether you need to stop taking supplements. Some supplements need 2 to 3 weeks to completely leave your body, and a few can cause serious problems during or after an operation.
  • If you are pregnant or breastfeeding, take only dietary supplements prescribed or approved by your doctor. Few dietary supplements have been studied for safety, so their effects on a growing fetus or infant are largely unknown.
  • Talk with your doctor before taking any self-prescribed remedies instead of medicine prescribed for you.
  • Do not depend on any non-prescription product to cure cancer or any other serious disease. No matter what the claim, if it sounds too good to be true, it probably is.
  • Follow the dosage limits on the label. Taking too much might cause harm or even death. And do not take a dietary supplement for any longer than recommended.
  • Never give a supplement to a baby or a child under the age of 18 without talking to the child’s doctor. The effects of many products in children are not known.

Finding trustworthy information about dietary supplements*

There’s a lot of misleading information out there. Even for those who are usually well informed, it can be hard to find reliable information about the safe use and potential risks of dietary supplements.

Along with the American Cancer Society, other sources of reliable information include:

National Cancer Institute’s Office of Cancer Complementary and Alternative Medicine
Offers in-depth information about complementary and alternative therapies with a focus on cancer. Includes sections on talking to your healthcare provider about CAM, information about specific therapies, and frequently asked questions.

National Institutes of Health’s Office of Dietary Supplements
Provides information about wise supplement use and detailed fact sheets about individual vitamins and supplements. Also has an app you can use to keep up with supplements on your smart phone; choose My Dietary Supplements Mobile App on the left menu bar.

National Center for Complementary and Integrative Health (NCCIH)
Has information on complementary and alternative therapy-related topics and clinical trials including a section with fact sheets about many herbs.

Memorial Sloan Kettering Cancer Center - About Herbs and Botanicals
Provides information about herbs, botanicals, supplements, and more, for consumers and health care professionals. Also offers the About Herbs mobile app for free.

US Food and Drug Administration – Dietary Supplements
Includes information about labels, rules, regulations, and more about dietary supplements. Includes information about reporting problems with dietary supplements.

*Inclusion on this list does not imply endorsement by the American Cancer Society.

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 journalists, 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: August 30, 2021

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