FAQ's on dietary supplements

Last updated: January 2011

Consumer Reports recently covered dangerous supplements as well as potentially useful dietary supplements. Those reports, and others, have led to a number of reader questions and comments about our supplement coverage. Here are our responses to some of the most frequently asked questions.

Who uses dietary supplements?
Dietary supplements have been taken by more than half of American adults; consumers spent $26.7 billion on supplements in 2009. Common motivations are to lose weight, stay healthy, and avoid the use of prescription drugs. Slightly more than half of older adults (ages 57 to 85) take supplements right along with their prescription medications. And more than half of respondents to a national Harris poll in 2002 said they believed—incorrectly—that supplements must be approved by a government agency before they can be sold to the public; that the government requires warning labels on supplements' potential side effects or dangers; and that manufacturers can't make safety claims without solid scientific support.

How are supplements covered on ConsumerReports.org?
Articles, recommendations, tests, and news coverage of supplements are done by the staff of Consumer Reports, often in consultation with outside medical experts.

Are there other reliable sources of information on supplements?
Yes. Reliable sources of information include:

While the Internet is a rich source of health information, it is also an easy vehicle for spreading hoaxes, myths, and rumors about alleged news, studies, products, or findings. If a site makes product claims that sound too good to be true, and provides information that is not written or reviewed by qualified health professionals, experts in the field, academia, government, or the medical community, it is unlikely to be a reliable source.

You mention an Airborne grant to educate consumers about supplements. What is it, and how will you use the money?
The Airborne Cy Pres Fund was established in 2010 through a legal settlement of a national class-action lawsuit regarding deceptive advertising practices by the makers of Airborne dietary supplements. Consumer Reports received a two-year grant from the fund to educate the public about dietary supplements. Beginning in November 2010, Consumer Reports began posting articles, news, and blogs about various supplements in both English and Spanish, available free on ConsumerReports.org and CR Espanol. See our AdWatch videos on supplement claims.

If there's so much information available, why do you often say there's not enough evidence to recommend a particular dietary supplement?
When we refer to a lack of evidence, we mean there are few if any scientific studies—in particular, the gold standard of medical research: the randomized, controlled trials—to support claims about a particular supplement. To be fair, lack of evidence doesn't necessarily mean something doesn't work. There's little financial incentive for manufacturers to bankroll large studies, since you can't necessarily patent an herb to recoup the costs.

But even in the cases when such studies are done, they probably prove only the efficacy of the particular formulation tested. In fact, what's on the label may not be what's in the bottle.

What do you mean by proven? When I have an upset stomach, I drink a cup of chamomile tea, and within a few hours, my stomach is calm again. Isn't that proof it works?
If you take a particular herb or product and experience relief from a particular symptom, it could mean only that both things happened in a similar time frame. It does not prove that one—taking a supplement—caused the other (resolution of symptoms).

Many conditions such as stomach upset are self-limiting, meaning that they come and go. What could happen is that someone has symptoms, wants to do something about them, and drinks a cup of herbal tea. Lo and behold, several hours later, he or she feels much better and attributes relief of symptoms to the tea, but it was really the natural course of stomach upset.

If something has been used for thousands of years, isn't that proof enough that it's safe?
Not necessarily. Herbs such as chaparral and coltsfoot have long been used to treat various ills. But as our story on dangerous supplements showed, coltsfoot has been shown to cause liver damage and cancer, while chaparral can leave you with liver damage and kidney problems. Certain health problems might not show up for years, so it's hard to judge safety without a long-term study. Other serious problems occur so infrequently that they can only be identified in a large study or by gathering numerous isolated case reports.

Why warn about supplements? Don't pharmaceutical drugs kill more people?
ConsumerReportsHealth.org is dedicated to providing safety and safe use information for drugs and supplements sold to consumers. We have taken a proactive stance in encouraging better surveillance and safety watches for pharmaceutical drugs. Drugs prescribed by your doctor must be proved effective, with an acceptable safety profile, by means of lab research and rigorous human clinical trials involving a minimum of several thousand people and several years. While virtually all medications have side effects and some risks, the benefits usually have been shown to outweigh the risks if they provide important symptom relief or preventive actions.

In contrast, dietary supplement manufacturers can introduce new products without providing the Food and Drug Administration with any testing for safety or efficacy. They do have to send the FDA a copy of the language used on the label. And while drug labels and package inserts must mention all possible adverse effects and interactions, supplement makers do not have to put safety warnings on the labels, even for products with known serious hazards.

Isn't the FDA supposed to reject any product that's not safe and keep it from being sold?
Even when serious safety problems are documented, it's difficult for the FDA to take prompt action to protect consumers. Unless the FDA meets a high standard of proof that a dietary supplement creates "a significant or unreasonable risk," it cannot ban it. For example, it took a decade to ban the ephedrine alkaloids used in weight-loss products, and during that time supplements containing ephedra were linked to thousands of adverse events. The FDA has also urged manufacturers to recall supplements that are contaminated with pharmaceutical drugs. This has occurred recently with many weight-loss supplements (laced with the now withdrawn prescription drug sibutramine) and with many sexual potency supplements (containing a chemical similar to sildenafil—the active ingredient of the prescription drug Viagra).

Since herbs are natural, can't I assume they're safe?
"Natural" should not be equated with safe. Hemlock and poisonous mushrooms are dangerous, despite being natural. The major protections that are in place for prescription and over-the-counter medicines don't apply to dietary supplements. Since supplements can be taken without professional supervision, and many times by people intent on preventing health problems, any safety concerns are particularly important, from a "first do no harm" point of view.

Even if there's no proof for, say, a supplement that's supposed to prevent type 2 diabetes, heart disease, or cancer, why shouldn't I take it just in case it does work?
It's against the law for companies to claim that any supplement can treat, prevent, or cure any disease except some nutrient-deficiency conditions. So if you see such a claim, it should make you wary. The Federal Trade Commission (FTC) regulates advertising for dietary supplements and most other products sold to consumers, and has taken action against companies that make such claims. Other reasons not to take supplements "just in case": herbal supplements may interact with prescription and/or over-the-counter drugs you're already taking; supplements may contain contaminants such as lead, mercury, or pesticides that can lead to an increased risk of cancer and other severe health consequences; and supplements can have serious side effects.

Are supplements sold in pharmacies better than the ones sold in grocery or health-food stores?
Since the current manufacturing practices were passed in 2007, supplement makers must follow certain regulations. But the FDA does not seem to have the resources to enforce those rules. Brands that have the "USP Verified" mark on the product indicate that the manufacturer has voluntarily asked the U.S. Pharmacopeia, a trusted nonprofit, private standards-setting authority, to verify the quality, purity, and potency of its raw ingredients or finished products. USP-verified products are relatively uncommon in the vast supplement marketplace, but it's a good place to start. USP maintains a list of verified products on its website.

Does the form of the supplement—whether it's in a tea, a tincture, or a pill—matter?
Yes. Not all forms of an herbal medicine produce the same effects. For example, tea made from saw palmetto probably has no health benefits, since the active compounds don't dissolve in water. And while the active chemicals in ginkgo biloba, white willow bark, and milk thistle do dissolve, even the strongest tea is probably too weak to do any good.

Further, different parts of the same herb can have different effects. Dandelion leaves may act as a diuretic, the roots as a laxative. While the Chinese eat ginkgo seeds, only ginkgo leaves contain the active compounds, and only processed ginkgo leaves are safe to take internally. And sassafras remedies are made from the root, the one part of the plant that's potentially carcinogenic.

Finally, the potency and purity of individual plants can differ appreciably, depending on how and where they're grown and how they're stored and handled.

More manufacturers are trying to standardize their products by combining batches and isolating the active compounds. But manufacturers often disagree on which ingredients to include and what dose to use. Analyses of ginseng and St. John's wort products, for example, have found radically different amounts of the active ingredients in different brands. And it's often impossible to spot the difference, since manufacturers are required to list only the plant and the part used, not the name or amount of the supposedly active ingredient.

Why do you advise talking to your doctor or pharmacist before taking any supplements?
Even a helpful product can be harmful in some situations, such as when you're pregnant or nursing, have a chronic disease, or are about to have surgery. And some dietary supplements might be fine on their own but interact with certain prescription or over-the-counter drugs. Your doctor or pharmacist can steer you away from such problems only if they know what supplements you're taking or plan to take. So create and maintain a list of all your medicines, including any over-the-counter drugs and supplements you may be taking, and bring it to your appointments.

Most physicians and pharmacists are also more likely to be a reliable source of information about supplements and potential interactions than staff in a store, who may be eager to make a sale. However, be leery of any health professional who sells supplements from his or her office, including chiropractors, doctors, natropaths, and nutritionists. Since those supplements are almost always sold at a profit, that creates a conflict of interest if the professional makes money on the sale. And consumers may be put in an awkward position and feel beholden to purchase the recommended supplements.

For these reasons the American Medical Association advises that if physicians do decide to distribute non-prescription health-related products to their patients, they should provide them free of charge or at cost. This removes the temptation of personal profit that can interfere with the physician's objective clinical judgment.

I had a bad reaction to a dietary supplement, but there's nothing about side effects on the package. How can I warn other people?
A law that took affect in December 2007 requires that supplement makers report serious adverse events to the FDA. But much more needs to be done to keep consumers safe. Anyone who experiences symptoms after taking a supplement should contact their doctor. If you've had a serious side effect, ask your doctor or pharmacist to report it to the FDA, do it yourself online or call 800-332-1088.

This report was made possible by a grant from the Airborne Cy Pres Fund, which was established through a legal settlement of a national class-action lawsuit (Wilson v. Airborne Health, Inc., et al.) regarding deceptive advertising practices.

E-mail Newsletters

FREE e-mail Newsletters!
Choose from cars, safety, health, and more!
Already signed-up?
Manage your newsletters here too.

Food News


Cars Build & Buy Car Buying Service
Save thousands off MSRP with upfront dealer pricing information and a transparent car buying experience.

See your savings


Mobile Get Ratings on the go and compare
while you shop

Learn more