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Dietary supplements are a topic of great public interest. Whether
you are in a store, using the Internet, or talking to people you
know, you may hear about supplements and claims of benefits for
health. How do you find out whether "what's in the bottle" is safe
to take and whether science has proven that the product does what it
claims? This fact sheet provides some answers.
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- What are dietary supplements?
- Why do people take supplements?
- Is using supplements considered conventional medicine
or complementary and alternative medicine (CAM)?
- How can I get science-based information on a
- If I am interested in using a supplement as CAM, how
can I do so most safely?
- I see the word "natural" on a lot of supplement
labels. Does "natural" always mean "safe"?
- Does the Federal Government regulate supplements?
- Is NCCAM supporting research on 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).
- Are taken by mouth.
- Contain a "dietary ingredient" intended to supplement the diet.
Examples of dietary ingredients include vitamins, minerals, herbs*
(as single herbs or mixtures), other botanicals, amino acids, and
dietary substances such as enzymes and glandulars.
- Come in different forms, such as tablets, capsules, softgels,
gelcaps, liquids, and powders.
- Are not represented for use as a conventional food or as a sole
item of a meal or the diet.
- Are labeled as being a dietary supplement.
* Linked terms are defined at the end of
this fact sheet.
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.
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People take supplements for many reasons. A scientific study on this topic
was published in 2002. In it, over 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? *|
||% of |
|Health/good for you
||Health/good for you
|Don't know/no reason specified
|Recommended by friend/family/media
||Don't know/no reason specified
* Adapted from 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. Copyright ©
2002, American Medical Association. All rights reserved.
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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
complementary and alternative medicine (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 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 nurses, physical therapists, and dietitians. Other
terms for conventional medicine include allopathy; Western,
mainstream, orthodox, and regular medicine; and
Complementary and Alternative Medicine
Health care practices and products that are not presently
considered to be part of conventional medicine are called CAM.
Complementary medicine is used together with
conventional medicine. Alternative medicine is used
in place of 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 (NCCAM), part of the National Institutes
of Health (NIH), is the Federal Government's lead agency for
scientific research on CAM.
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There are several ways to get information on supplements that is 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 yourself whether there are any scientific research findings
on the CAM supplement you are interested in. NCCAM and other Federal agencies
have free publications, clearinghouses, and databases with this information.
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Here are some points to keep in mind:
- It is important to talk to your health care provider (or providers, if
you have more than one) about the supplement. This is for your safety and
a complete treatment plan. It is especially important to talk to
your provider if you:
- Are thinking about replacing your regular medical care with one or
- 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 thinking about giving a child a supplement. Many products being
marketed for children have not been tested for their safety and effectiveness
- 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 can also report your experience to the U.S.
Food and Drug Administration's (FDA) MedWatch program, which tracks consumer
safety reports on supplements.
- If you are considering or using herbal supplements, there are some special
safety issues to consider.
Supplements and Drugs Can Interact
- St. John's wort can increase the effects of prescription drugs
used to treat depression. It can also interfere with drugs used
to treat HIV infection, to treat cancer, for birth control, or to
prevent the body from rejecting transplanted organs.
- Ginseng can increase the stimulant effects of caffeine
(as in coffee, tea, and cola). It can also lower blood sugar
levels, creating the possibility of problems when used with
- Ginkgo, taken with anticoagulant or antiplatelet drugs,
can increase the risk of bleeding. It is also possible that
ginkgo might interact with certain psychiatric drugs and
with certain drugs that affect blood sugar
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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. The FDA found these products of concern because
- Could damage health--in some cases severely.
- Were contaminated--with other unlabeled herbs, pesticides, heavy metals,
or prescription drugs.
- Interacted dangerously with prescription drugs.
Examples of Supplements
That Have Carried FDA Cautions About Safety
GHB (gamma hydroxybutyric acid), GBL (gamma
butyrolactone), and BD (1,4-butanediol)|
Some "dieter's teas" |
Certain products, marketed for sexual enhancement
and claimed to be "natural" versions of the drug
Viagra,® which were found to contain an unlabeled drug
(sildenafil or tadalafil).|
PC SPES and SPES|
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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 manufacturer does not have to prove supplement
- The FDA does not analyze the content of dietary
- 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.
In March 2003, the FDA published new proposed guidelines for
supplements that would require manufacturers to avoid contaminating
their products with other herbs, pesticides, heavy metals, or
prescription drugs. The guidelines would also require supplement
labels to be accurate. These new guidelines could take effect as
early as 2004.
The Federal Government also regulates supplement advertising,
through the Federal Trade Commission. It requires that all
information about supplements be truthful and not mislead
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.
- 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.
- Be contaminated (as discussed in Question 6).
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Yes, NCCAM is funding most of the nation's current research aimed
at increasing scientific knowledge about supplements--including
whether they work; if so, how they work; and how purer and more
standardized products could be developed. Among the substances that
researchers are studying are:
- Yeast-fermented rice, to see if it can lower cholesterol
levels in the blood
- Soy, to see if it slows the growth of tumors
- Ginger and turmeric, to see if they can reduce inflammation
associated with arthritis and asthma
- Chromium, to better understand its biological effects and
impact upon insulin in the body, possibly offering new pathways to
treating type 2 diabetes
- Green tea, to find out if it can prevent heart
NCCAM is also sponsoring or cosponsoring clinical trials on supplements,
- Glucosamine hydrochloride and chondroitin sulfate, to find out
if they relieve knee pain from osteoarthritis
- Black cohosh, to see if it reduces hot flashes and other
symptoms of menopause
- Echinacea, to see if it shortens the length or lessens the
severity of colds in children
- Garlic, to find out if it can lower moderately high
- Ginkgo biloba, to determine whether it prevents or
delays decline in cognitive (thinking) function in people aged 85
- Ginger, to confirm whether it eases nausea and vomiting after
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Center for Food Safety
and Applied Nutrition (CFSAN)
Federal Trade Commission (FTC)
Office of Dietary Supplements
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Amino acid: Building block of
Botanical: See "herb."
"Botanical" is a synonym for "herb."
Clinical trials: Research studies
in which a treatment or therapy is tested in people to see whether
it is safe and effective.
Depression: An illness that
involves the body, mood, and thoughts. The symptoms of depression
often include feelings of sadness, hopelessness, or pessimism; and
changes in sleep, appetite, and thinking.
Enzymes: Proteins that speed up
chemical reactions in the body.
Glandulars: Dietary ingredients
or supplements that are made from the glands of animals.
Heavy metals: A class of metals that,
in chemical terms, have a density at least five times that of water.
They are widely used in industry. A few examples of heavy metals
that are toxic and have contaminated some dietary supplements are
lead, arsenic, and mercury.
Herb: A plant or plant part that is
used for its flavor, scent, and/or therapeutic properties.
Peer reviewed: Reviewed before
publication by a group of experts in the same field.
provided by individuals who claim to have been helped or cured by a
particular product. The information provided lacks the necessary
elements to be evaluated in a rigorous and scientific manner and is
not used in the scientific literature.
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