Topic Overview

What are dietary supplements?

In the United
States, dietary supplements are substances you eat or drink. They can be
vitamins, minerals, herbs or other plants,
amino acids (the individual building blocks of
protein), or parts of these substances. They can be in pill, capsule, tablet,
or liquid form. They supplement (add to) the diet and should not be considered
a substitute for food.

Dietary supplements are widely available in
the United States in health food stores, grocery stores, pharmacies, on the
Internet, and by mail. People commonly take them for health-related reasons.
Common dietary supplements include vitamins and minerals (such as vitamin C or
a multivitamin), botanicals (herbs and plant products, such as St. John’s
wort), and substances that come from a natural source (such as omega-3 fatty

Makers of dietary supplements cannot legally say that
dietary supplements can diagnose, cure, treat, or prevent disease. But they can
say that they contribute to health maintenance and well-being.

People have used the active ingredients in dietary supplements for
thousands of years to help health and to treat illness. Sometimes those
supplements are the basis for some of today’s common medicines. For example,
people have used willow bark tea for centuries to relieve fever. Pharmaceutical
companies eventually identified the chemical in willow bark that relieved fever
and used that knowledge to produce aspirin.

The U.S. Food and Drug
Administration (FDA) does not regulate dietary supplements in the same way that
it regulates medicine. A dietary supplement can be sold without research on how
well it works.

What are dietary supplements used for?

People use
dietary supplements for many health conditions.

  • Historically, people have used herbal medicines to prevent illness, cure
    infection, relieve fever, and heal wounds. Herbal medicines can also treat
    constipation, ease pain, or act as relaxants or stimulants. Research on some
    herbs and plant products has shown that they may have some of the same effects
    that conventional medicines do, while others may have no effect or may be
  • Researchers have studied some natural products and have found
    them to be useful. Omega-3 fatty acids, for example, may help lower
    triglyceride levels.

Researchers have found that some supplements do not help prevent or treat certain health problems. For example, beta-carotene and vitamin E do not lower risk of heart disease or heart attack.

Are dietary supplements safe?

Not all herbs and
supplements are safe. If you are unsure about the safety of a supplement or
herb, talk to your doctor, pharmacist, or dietitian.

Always tell
your doctor if you are using a dietary supplement or if you are thinking about
combining a dietary supplement with your conventional medical treatment. It may
not be safe to forgo your conventional medical treatment and rely only on a
dietary supplement. This is especially important for women who are pregnant or

When using dietary supplements, keep in mind the

  • Like conventional medicines, dietary
    supplements may cause side effects, trigger allergic reactions, or interact
    with prescription and nonprescription medicines or other supplements you might
    be taking. A side effect or interaction with another medicine or supplement may
    make other health conditions worse.
  • The way dietary supplements are
    manufactured may not be standardized. Because of this, how well they work or
    any side effects they cause may differ among brands or even within different
    lots of the same brand. The form of supplement that you buy in health food or
    grocery stores may not be the same as the form used in research.
  • Other than for vitamins and minerals, the long-term effects of
    most dietary supplements are not known.


Other Works Consulted

  • Reichenbach S, et al. (2007). Meta-analysis: Chondroitin for osteoarthritis of the knee or hip. Annals of Internal Medicine, 146(8): 580-590.
  • Rozendaal RM, et al. (2008). Effect of glucosamine sulfate on hip osteoarthritis. Annals of Internal Medicine, 148(4): 268-277.
  • Sawitzke AD, et al. (2008). The effect of glucosamine and/or chondroitin on the progression of knee osteoarthritis. Arthritis and Rheumatism, 58(10): 3183-3191.
  • Thomson CA (2012). Food and nutrient delivery: Bioactive substances and integrative care. In LK Mahan et al., eds., Krause’s Food and the Nutrition Care Process, 13th ed., pp. 291-305. St Louis, MO: Saunders.
  • U.S. Preventive Services Task Force (2014). Vitamin, mineral, and multivitamin supplements for the primary prevention of cardiovascular disease and cancer. U.S. Preventive Services Task Force. Accessed March 28, 2014.
  • Whitney E, Rolfes SR (2011). Vitamin and mineral supplements. In Understanding Nutrition, 12th ed., pp. 346-352. Belmont, CA: Wadsworth.


ByHealthwise Staff
Primary Medical Reviewer Adam Husney, MD – Family Medicine

Current as ofMarch 3, 2017

Current as of:
March 3, 2017