Dietary Supplements: What You Should Know

By Susan Harms, R.Ph., M.P.H., Ph.D.
Jan. 20, 2005

The number of people taking dietary supplements for prevention and treatment of health problems has increased dramatically over the past decade. But because the U.S. Food and Drug Administration (FDA) regulates dietary supplements as foods rather than drugs, supplement manufacturers are not required to meet the same strict standards of safety and effectiveness that are required for prescription and over-the-counter medications. As a result, consumers need to be aware that products may vary widely from manufacturer to manufacturer in terms of strength and ingredients.

Supplements come in capsule, tablet, powder, or liquid form, and include vitamins, minerals, herbs or other botanicals, amino acids, and other substances. Some supplements, such as most vitamins and minerals, have become part of traditional medicine over the years. Herbs and other botanicals remain part of what is known as “complementary and alternative medicine” or CAM.

While ingesting either a traditional medication or a dietary supplement imposes some degree of risk, the risks and concerns with herbs are different than those found with traditional drugs and most vitamins and minerals. That is because herbs and drugs differ in some fundamental ways. For example, traditional drugs are manufactured under highly controlled conditions, while botanicals are subject to natural variations.

Side Effects

Many consumers don’t realize that supplements may produce side effects and interact with other medications, just as traditional drugs do. Often people do not associate ill effects with supplement use, either because they believe supplements are harmless or because their symptoms seem unrelated to what they are treating. For example, Ginseng, usually used to increase stamina and concentration, can raise blood pressure to unsafe levels.

If you are taking dietary supplements and have developed unusual symptoms, ask a nurse, doctor, or pharmacist if they could be related to supplement use.

Interactions

Interactions between supplements and medications and between supplements and medical conditions are common. It pays to be aware of possible interactions before initiating treatment. Ginkgo, for example, has the capacity to thin blood, which can be problematic for patients already on a prescription blood thinner such as Coumadin.

What can Consumers Do?

Consumers should read supplement labels closely, while remembering that labels cannot always be relied upon to provide complete or accurate information. In some cases, it has been found that the actual amount of active ingredient was significantly more or less than what was listed on the label. Because there are no standards for supplements, the consumer may find a wide range of doses recommended between various products, especially among herbal products. The best practice is to consult an outside reference for dosage recommendations rather than relying solely on product labels. It is also wise to seek advice from your nurse, doctor, or pharmacist. The label information may provide them with additional knowledge about that particular product that will help guide its use.

Dietary supplements offer an additional and potentially beneficial treatment choice, with the provision that they are granted the same respect as traditional medications. In choosing a supplement, though, the most prudent advice is caveat emptor, or “buyer beware.”

Susan Harms is a pharmacist and senior research associate in the Health Services Research, Policy, and Administration division of the School of Public Health, University of Minnesota. This column is an educational service of the University of Minnesota. Advice presented should not take the place of an examination by a health-care professional. To ask a health-care expert at the University a question or for more health-related information, go to http://www.healthtalk.umn.edu/