What Are Dietary Supplements?

Dietary supplements (also called nutritional supplements, or supplements for short) were defined in a law passed by Congress in 1994 (see the box below).^1,2

About Dietary Supplements A dietary supplement must meet all of the following conditions: It is a product (other than tobacco) that is intended to supplement the diet and that contains one or more of the following: vitamins, minerals, herbs or other botanicals, amino acids or any combination of the above ingredients. It is intended to be taken in tablet, capsule, powder, softgel, gelcap or liquid form. It is not represented for use as a conventional food or as a sole item of a meal or the diet. It is labeled as being a dietary supplement.

Dietary supplements are sold in grocery, health food, drug and discount stores, as well as through mail-order catalogs, TV programs, the Internet and direct sales.

Why Do People Take Supplements?

People take supplements for many reasons. A scientific study on this topic was published in 2002.³ In it, more than 2,500 Americans reported on supplements they used (given the categories of vitamins/minerals and herbal products/natural supplements) and for what reasons. Their responses are summarized in the table below.

Supplements: Why Taken?
Vitamins/Minerals	% of Responses	Herbals/Supplements	% of Responses
Health/good for you	35	Health/good for you	16
Dietary supplement	11	Arthritis	7
Vitamin/mineral supplement	8	Memory improvement	6
Prevent osteoporosis	6	Energy	5
Physician recommended	6	Immune booster	5
Prevent colds/influenza	3	Joint	4
Don't know/no reason specified	3	Supplement diet	4
Immune booster	2	Sleep aid	3
Recommended by friend/family/media	2	Prostate	3
Energy	2	Don't know/no reason specified	2
All others	22	All others	45

Is Using Supplements Considered Conventional Medicine or Complementary and Alternative Medicine (CAM)?

Some uses of dietary supplements have become part of conventional medicine. For example, scientists have found that the vitamin folic acid prevents certain birth defects, and a regimen of vitamins and zinc can slow the progression of the eye disease age-related macular degeneration.

On the other hand, some supplements are considered to be CAM — either the supplement itself or one or more of its uses. An example of a CAM supplement would be an herbal formula that claims to relieve arthritis pain, but has not been proven to do so through scientific studies. An example of a CAM use of a supplement would be taking 1,000 milligrams of vitamin C per day to prevent or treat a cold, as the use of large amounts of vitamin C for these purposes has not been proven.

Conventional Medicine Conventional medicine is medicine as practiced by holders of M.D. (medical doctor) or D.O. (doctor of osteopathy) degrees and by their allied health professionals, such as physical therapists, psychologists and registered nurses. Other terms for conventional medicine include allopathy; Western, mainstream, orthodox and regular medicine; and biomedicine. Complementary and Alternative Medicine (CAM) CAM is a group of diverse medical and health care systems, practices and products that are not presently considered to be part of conventional medicine. Complementary medicine is used together with conventional medicine, and alternative medicine is used in place of conventional medicine. Some health care providers practice both CAM and conventional medicine. There is scientific evidence for the effectiveness of some CAM treatments. But for most, there are key questions yet to be answered through well-designed scientific studies, such as whether they are safe and work for the diseases or conditions for which they are used. The National Center for Complementary and Alternative Medicine, a part of the National Institutes of Health, is the federal government's lead agency for scientific research on CAM.

How Can I Get Science-Based Information on a Supplement?

There are several ways to get information on supplements that are based on the results of rigorous scientific testing, rather than on testimonials and other unscientific information.

• Ask your health care provider. Even if your provider does not happen to know about a particular supplement, he can access the latest medical guidance about its uses and risks.

• Dietitians and pharmacists also have helpful information.

• You can find out if there are any scientific research findings on the CAM supplement in which you are interested. NCCAM and other federal agencies have free publications, clearinghouses and databases with this information.

Here are some points to keep in mind:

• Tell your health care providers about any complementary and alternative practices you use. Give them a full picture of what you do to manage your health. This will help ensure coordinated and safe care. It especially is important to talk to your provider if you:
  • Are thinking about replacing your regular medical care with one or more supplements.

  • Are taking any medications (whether prescription or over-the-counter). Some supplements have been found to interact with medications.

  • Have a chronic medical condition.

  • Are planning to have surgery. Certain supplements may increase the risk of bleeding or affect anesthetics and painkillers.

  • Are pregnant or nursing a baby.

  • Are considering giving a child a dietary supplement. Supplements can act like drugs, and many have not been tested in pregnant women, nursing mothers or children.⁴

• Do not take a higher dose of a supplement than what is listed on the label, unless your health care provider advises you to do so.

• If you experience any side effects that concern you, stop taking the supplement, and contact your provider. You also can report your experience to the U.S. Food and Drug Administration's MedWatch program, which tracks consumer safety reports on supplements.

Supplements and Drugs Can Interact St. John's wort can increase the effects of prescription drugs used to treat depression. It also can interfere with drugs used to treat HIV infection, to treat cancer, for birth control, or to prevent the body from rejecting transplanted organs.5 Ginseng can increase the stimulant effects of caffeine (as in coffee, tea and cola). It also can lower blood sugar levels, creating the possibility of problems when used with diabetes drugs.5 Ginkgo, taken with anticoagulant or antiplatelet drugs, can increase the risk of bleeding. It also is possible that ginkgo might interact with certain psychiatric drugs and with certain drugs that affect blood sugar levels.5

I See the Word "Natural" on a Lot of Supplement Labels. Does "Natural" Always Mean "Safe"?

There are many supplements, as well as many prescription drugs, that come from natural sources and are both useful and safe. However, "natural" does not always mean "safe" or "without harmful effects." For example, consider mushrooms that grow in the wild — some are safe to eat, while others are poisonous.

The FDA issues warnings about supplements that pose risks to consumers, including those used for CAM therapies. A sample list is in the box below^6,7. The FDA found these products of concern because they:

• Could damage health — in some cases severely.

• Were contaminated — with other unlabeled herbs, pesticides, heavy metals or prescription drugs.

• Interacted dangerously with prescription drugs.

Does the Federal Government Regulate Supplements?

Yes, the federal government regulates supplements through the FDA. Currently, the FDA regulates supplements as foods rather than drugs. In general, the laws about putting foods (including supplements) on the market and keeping them on the market are less strict than the laws for drugs. Specifically:

• Research studies in people to prove a supplement's safety are not required before the supplement is marketed, unlike for drugs.

• The manufacturer does not have to prove that the supplement is effective, unlike for drugs. The manufacturer can say that the product addresses a nutrient deficiency, supports health or reduces the risk of developing a health problem, if that is true. If the manufacturer does make a claim, it must be followed by the statement "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."

• The FDA does not analyze the content of dietary supplements.

• At this time, supplement manufacturers must meet the requirements of the FDA's Good Manufacturing Practices (GMPs) for foods. GMPs describe conditions under which products must be prepared, packed and stored. Food GMPs do not always cover all issues of supplement quality. Some manufacturers voluntarily follow the FDA's GMPs for drugs, which are stricter.

• Some manufacturers use the term "standardized" to describe efforts to make their products consistent. However, U.S. law does not define standardization. Therefore, the use of this term (or similar terms such as "verified" or "certified") does not guarantee product quality or consistency.

• If the FDA finds a supplement to be unsafe once it is on the market, only then can it take action against the manufacturer and/or distributor, such as by issuing a warning or requiring the product to be removed from the marketplace.

The federal government also regulates supplement advertising, through the Federal Trade Commission. It requires that all information about supplements be truthful and not mislead consumers.

What's in the Bottle Does Not Always Match What's on the Label A supplement might: Not contain the correct ingredient (plant species). For example, one study that analyzed 59 preparations of echinacea found that about half did not contain the species listed on the label.8 Contain higher or lower amounts of the active ingredient. For example, an NCCAM-funded study of ginseng products found that most contained less than half the amount of ginseng listed on their labels.9 Be contaminated.

References

1. Dietary Supplement Health and Education Act of 1994. Food and Drug Administration Web site. Accessed at fda.gov/opacom/laws/dshea.html on April 14, 2003.
2. Dietary supplements: overview. U.S. Food and Drug Administration, Center for Food Safety and Applied Nutrition Web site. Accessed at cfsan.fda.gov/~dms/supplmnt.html on August 20, 2003.
3. Kaufman DW, Kelly JP, Rosenberg L, et al. Recent patterns of medication use in the ambulatory adult population of the United States: the Slone survey. Journal of the American Medical Association. 2002;287(3):337-344.
4. Federal Trade Commission. Promotions for kids' dietary supplements leave sour taste. Federal Trade Commission Web site. Accessed at ftc.gov/opa/2004/06/kidsupp.htm on May 2, 2003.
5. Natural Medicines Comprehensive Database. Natural Medicines Comprehensive Database Web site. Accessed on August 20, 2003.
6. MedWatch: the FDA safety information and adverse event reporting program. U.S. Food and Drug Administration Web site. Accessed at fda.gov/medwatch on August 20, 2003.
7. Dietary supplements: warnings and safety information. U.S. Food and Drug Administration, Center for Food Safety and Applied Nutrition Web site. Accessed at cfsan.fda.gov/~dms/ds-warn.html on April 14, 2003.
8. Gilroy CM, Steiner JF, Byers T, et al. Echinacea and truth in labeling. Archives of Internal Medicine. 2003;163(6):699-704.
9. Harkey MR, Henderson GL, Gershwin ME, et al. Variability in commercial ginseng products: an analysis of 25 preparations. American Journal of Clinical Nutrition. 2001;73(6):1101-1106.

Updated: March 13, 2007

Related Articles

• Overview of Dietary Supplements
• Overview of Botanical Dietary Supplements
• What Is Complementary and Alternative Medicine?