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date: 6/14/2006
Nutritional Supplements: Your Questions Answered
With so many products to choose from in your local health-food store, how do you know which ones are worth buying? We answer the most common questions about nutritional supplements.
Subscribe to for more information about thousands of natural remedies and nutritional supplements, including the facts about their safety and effectiveness.
Does a supplement a day keep the doctor away--or hasten your visit to his or her office? Americans spend billions of dollars on natural remedies each year. But as you consider the dizzying array of products in the health-food aisle, think twice about their safety and efficacy. Here are the most frequently asked questions about what to watch out for, what works, and when to skip natural remedies altogether.

Q: What's the difference between a nutritional supplement and a drug?
In some respects, not much. Both can have powerful pharmacological effects and cause problems if taken incorrectly. Some conventional medicines are actually derived from plants, and many supplements are sold as concentrates that are virtually indistinguishable from drugs.
How drugs and supplements are viewed by the Food and Drug Administration (FDA) is another matter entirely. Under the Dietary Supplement Health and Education Act (DSHEA), the FDA essentially treats supplements as if they were foods. DSHEA defines nutritional supplements as products taken by mouth that contain an ingredient intended to supplement the diet.
Those ingredients could include vitamins, minerals, or natural biological substances such as enzymes. They can come in a variety of forms, including extracts and concentrates, and as tablets, capsules, powders, or liquids.
Drugs, on the other hand, are legally defined as substances intended to diagnose, treat, or prevent disease. To learn more, check out the FDA's overview of supplements.

Q: Does the government regulate supplements?
Just barely--under DSHEA most supplements get less scrutiny from the FDA than a pack of cough drops. The 1994 law, whose passage was secured in part through heavy lobbying from the supplements industry, restricts the FDA's authority over supplements, as long as companies are careful not to claim that their products treat, prevent, or cure disease. The law has left consumers without the protections surrounding the manufacture and marketing of over-the-counter or prescription medications.
Drugmakers must spend millions on clinical tests to show that a product works and is safe before the FDA will allow it on the market. Supplement manufacturers can launch products without any testing at all just by sending the FDA a copy of the language on the label. In fact, DSHEA makes it the FDA's responsibility to prove that a supplement on the market isn't safe; so far, that's happened just once, with the hazardous weight-loss and energy supplement ephedra. The exceptions to the rule are those few supplements that weren't sold in the U.S. before DSHEA went into effect. Manufacturers of such "new dietary ingredients" must provide the FDA with evidence of a product's safety.

Q: But aren't nutritional supplements safer than prescription drugs because they're natural and chemical-free?
Though consumers often think "natural" means pure and unprocessed, some supplements are anything but. Independent tests have found them contaminated with unwanted, potentially harmful ingredients such as heavy metals, pesticides, and bacteria; a few have even been found to contain prescription drugs. While the FDA monitors drug manufacturing plants to make sure products are of a good and uniform quality, there's currently no requirement that supplement makers follow these same so-called "good manufacturing practices." The purity, potency, and identity of a supplement may vary from product to product, and you may not know if other ingredients have been added. Consumer Reports tests have found that bottles don't contain what their labels say they do or in the dosage they purport to have. And even in her rawest form, Mother Nature can pack a dangerous punch; many plants--think poison ivy and hemlock--are poisonous.

Q: What are the most popular supplements? And, more important, do they work?
Multivitamins, the top-selling supplements, are also by far the safest and best studied. But while they have clear benefits for those with special nutritional needs--for example, pregnant women or people with nutrient-depleting diseases--whether others need to take them is still up for debate. Experts recently convened by the National Institutes of Health determined there's not enough evidence to say whether multivitamins help prevent diseases like cancer, or even enhance everyday vim and vigor. And it's probably not necessary to take them if you have a healthy diet. In fact, some people actually exceed the safe limits of certain vitamins (one reason to steer clear of megadoses), which poses its own health risks. (For recommended allowances, visit the International Food Information Council (IFIC) Foundation's Web site.
Another big seller? Calcium. Studies suggest that, in addition to strengthening bones, it may also ease symptoms of premenstrual syndrome, reduce the risk of developing colon polyps, and stave off other health problems. Most people don't get the recommended amount of calcium, and for women over age 50 and men over 65 a supplement can help. But if you're a younger adult looking to increase your intake, your best bet is to focus instead on calcium-rich foods that are also high in other nutrients. Probiotic supplements, which contain the "friendly" bacteria normally found in our digestive system, are also popular. Though research has offered few conclusive findings, studies suggest probiotic bacteria may offer relief from some digestive disorders, such as antibiotic associated diarrhea, and may even help alleviate atopic eczema in some children.
For more on which nutritional supplements work, check this site as well as Consumer Reports on Health and But keep in mind that because of the lack of proper clinical testing, we simply don't know how effective many of the products on the market are.

Q: Which supplements can I take to lose weight?
Alas, none. No supplement has consistently demonstrated through proper clinical studies that it can help people lose weight. And some can be dangerous. For instance, weight-loss supplements that pair caffeine with bitter orange, a stimulant that marketers have been using in place of ephedra, can spur potentially dangerous increases in blood pressure and heart rate.

Q: Are some other nutritional supplements also unsafe to take?
Yes. Kava, which has sedative-like effects and is mainly used for anxiety or insomnia, has been linked to liver damage. Yohimbe, a sexual stimulant, has been linked to heart and respiratory problems. And the FDA has banned imports of aristolochia, a herb linked to kidney failure and cancer, though products claiming to contain the ingredient are still sold online. For more supplements to watch out for, see the Consumer Reports story, "Dangerous Supplements: Still at Large." Also, some supplements, like some drugs, may occasionally cause or worsen various diseases and disorders when used long-term. Ginger, ginkgo, and ginseng for example, may lead to a worsening of bleeding disorders.

Q: Can I take natural supplements if I'm also taking prescription drugs and over-the-counter medications?
Some supplements interfere with prescription medications or cause dangerous side effects when paired with drugs. St. John's wort, for example, may reduce the effectiveness of some blood pressure drugs or cause birth control pills to fail. Ginseng and gotu kola may excessively lower blood sugar in people taking diabetic drugs to control sugar levels. Be sure to let your doctor know which supplements you're taking--even if you think they're harmless.

Q: Can I take supplements if I'm about to have an operation?
Not a good idea. Because certain supplements may prolong the effects of anesthesia, cause excessive bleeding, or raise blood pressure, the American Society of Anesthesiologists recommends discontinuing use of all supplements at least two weeks before a procedure.

Q: Are supplements safe for pregnant women and children?
In general, natural supplements are poorly studied compared with conventional drugs. And, indeed, conventional drugs are poorly studied when it comes to pregnant women, says Dr. Phillip Gregory, co-editor of the Natural Medicines Comprehensive Database, a compendium of scientifically validated information on some 14,000 nutritional supplement products (available in a consumer version to subscribers of Consumer Reports Health). So if you're pregnant, avoid consuming any supplements other than your prenatal vitamins.
The same logic follows for children: With few exceptions most products have been studied only in adults, if at all, so we don't know for certain how they may affect children, who are more sensitive to druglike effects to begin with. "Unless there's a good reason to give your child a supplement--and there usually isn't--then don't," Gregory says.

Q: What supplement brands should I look for?
Products from many manufacturers have been found to have inconsistent ingredients, Gregory says. Still, it may be a good strategy to pick a well-known national manufacturer over a lesser-known brand. Bigger companies generally have more resources to make a product and more of a reputation to protect. Consumer Reports tests of various supplements have found mainstream brands to be more consistent in quality, while many of the no-name brands that are ubiquitous in dollar stores failed to contain the labeled amount of at least one nutrient or did not adequately dissolve. You can also look for a product with a quality control seal. The U.S. Pharmacopeia (USP), a private nonprofit group that sets standards for pharmaceuticals in the U.S., has a verification program to ensure that supplement manufacturers meet certain guidelines. Products that get the USP seal are also subject to random off-the-shelf tests. A few organizations like the National Nutritional Foods Association and also issue seals, but you should check the organizations' Web sites to find out exactly what their criteria are.

Q: Where can I find reliable information on supplements?
Much of what you'll find on the Internet--not to mention what the store clerk will tell you for a quick sale--may be inaccurate. For reliable information, check out dietary supplement information at the National Institutes of Health; the National Center for Complementary and Alternative Medicine; and Memorial Sloan Kettering Cancer Center. Consumer Reports Health subscribers have access to Natural Medicine Ratings provided for consumers by the Natural Medicines Comprehensive Database.

This site is for your information only. For medical advice, consult a health professional.