What You Should Know About Dietary Supplements

Medically Reviewed

An estimated 18 percent of Americans—nearly 60 million—use botanical, or herbal, preparations with the expectation that the products will protect or improve their health. But the purported benefits of dietary supplements are dubious and the products can even be harmful.

Many people assume that dietary supplements are inherently safe because they’re sold without a prescription. This is particularly the case for herbal products, which some people perceive as “natural” and therefore safer than products made with chemicals. But some supplements contain biologically active compounds that can cause serious adverse effects, whether used alone or in combination with prescriptions or over-the-counter drugs. That can trigger interactions that may enhance, reduce or eliminate the effects of a drug in ways that are largely unknown.

Loose regulation

Dietary supplements, intended to maintain health but not treat disease, aren’t considered to be drugs by the Food and Drug Administration. As a result, botanicals are only loosely regulated and not subject to the same rigorous testing as traditional medications. That leaves the effectiveness, quality and safety of dietary supplements questionable. With that in mind, here are some facts you should consider if you’re currently taking, or considering taking, an herbal supplement:

■ Few well-designed clinical trials have been performed on dietary supplements. In most cases, not enough scientific evidence exists to draw conclusions about the safety and effectiveness of herbal products.

■ Dietary supplements typically contain multiple ingredients difficult to isolate and produce in standardized amounts. (Conventional drugs are synthesized in labs using standardized methods to ensure batch-to-batch consistency and quality control.) Consequently, the active ingredients in herbal products prepared by different—or even the same—manufacturers can vary substantially.

■ Dose recommendations vary widely among brands because so little data are available about effective dosages.

■ Potency varies among the many forms of herbal products, such as tablets and capsules, liquid and solid extracts, powders, fresh or dried products, tea bags, tinctures, lotions and gels. Dosage strengths vary depending on the part of the plant from which ingredients are obtained: petals, seeds, stems, roots, leaves.

■ Related but not identical species of the same plant may be used in products marketed as the same. For instance, at least three species of echinacea are used in herbal products, resulting in different chemical makeup among products.

■ Labels may be inaccurate. Discrepancies are common between the ingredients listed on the label and what the product actually contains.

■ A dietary supplement’s effectiveness can be influenced by the botanical’s harvesting and storage conditions, such as the climate it was raised in and the length of time it was stored.

■ Botanical manufacturers are responsible for monitoring their own products’ potency and purity. They must guarantee their products contain the proper ingredients in the proper doses; aren’t contaminated with potentially harmful substances such as metals, allergens and pesticides; and are adequately packaged and labeled. However, few FDA safeguards are in place to ensure these rules are followed.