Dietary Supplements or Drugs: Know What You're Getting

By Timothy Tracy, Ph.D.

In some ways, there's no difference between dietary supplements, such as ginkgo biloba and St. John's Wart, and mainstream over-the-counter and prescription medications. All are intended to produce an effect on the body, all may affect your health, and all have the potential to interact with medications you're taking -- sometimes dangerously.

But that's where the similarities end.

The manufacture of over-the-counter and prescription medications is closely regulated by the Food and Drug Administration (FDA). Manufacturers of these drugs must conduct testing and follow strict standards to ensure safety, effectiveness and consistency of the drug. Put simply, the manufacturer must prove that the last tablet in the bottle works as well as the first.

Once the FDA gives its approval, a drug's label can claim that the prescribed dosage will treat or cure whatever ailment it was designed for.

Although dietary supplements are often taken to address health concerns as well, the FDA does not regulate companies that manufacture them in the same way it regulates drug manufacturers. Dietary supplements are products taken by mouth that contain an ingredient or ingredients intended to supplement the diet. These ingredients may include: vitamins, minerals, herbs or botanicals, amino acids, organ tissues, and other substances known as enzymes, glandulars, and metabolites. They must be labeled "dietary supplement."

The FDA requires that dietary supplements be safe (though there is no approval process for this determination). There is no guarantee that the first tablet or drop from a bottle will have the same composition as the second, third or last tablet or drop. The first tablet you take could have none of the effective ingredient while the second has twice the amount it's supposed to have.

Dietary supplements fall under the Dietary Supplement Health and Education Act (DSHEA). This dictates that dietary supplements can't make specific claims that they treat or cure a specific condition, unless the claim is substantiated by evidence. Supplement manufacturers can claim their products will help you feel better or improve a body function such as digestion.

Those taking a dietary supplement need to remember that it can interact with other drugs you may be taking. The FDA gives the following example that involves blood thinners. Coumadin (a prescription blood thinner), aspirin (an OTC drug), and ginkgo biloba and Vitamin E (both dietary supplements) all thin the blood. If taken together they can increase the chance for internal bleeding. To avoid dangerous interactions, always tell your physician if you're taking a dietary supplement.

At my lab at the University of Minnesota, my colleagues and I are currently studying drugs that don't behave in the expected manner within the body. We hope to develop a set of rules that will allow prediction of how these drugs will behave in the body.

This research, funded by a $1 million grant from the National Institutes of Health, could greatly reduce the harm caused by drug (and supplement) interactions.

Timothy Tracy, Ph.D., is head of the Department of Clinical and Experimental Pharmacology at the University of Minnesota College of Pharmacy and is a member of the University's Center of Excellence in Women's Health.

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. For more health-related information, go to http://www.healthtalk.umn.edu.