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Copyright 2013 Natural Standard (
March 2012

What Are the Limitations of Dietary Supplement Research?

According to a recent editorial written by Antoine Al-Achi, an associate professor in the Department of Pharmaceutical Sciences at Cambell University College of Pharmacy and Health Sciences, the increased use of dietary supplements and other forms of "botanical medicine" requires that better quality research is performed regarding the safety and effectiveness of these therapies.

Al-Achi explains that, although the Dietary Supplements Health and Education Act was established in 1994 in response to the increased use of herbal medicine in health care, the act was written with the assumption that dietary supplements would be used to complement a regular diet rather than to treat medical conditions.

As a result, dietary supplements are not evaluated by the U.S. Food and Drug Administration (FDA) to the same level or detail as drugs and pharmaceutical agents. Instead, the safety of dietary supplements is monitored by the FDA after the product has been sold to consumers for use.

According to Al-Achi, one of the most important, yet often overlooked, safety issue associated with dietary supplement use is the possibility for negative interactions between dietary supplements and other drugs. Only 25 percent of patients taking dietary supplements report this use to their doctors, yet clinical studies have shown that certain herbs or supplements may interact with commonly used drugs, such as anti-diabetic or blood thinner agents.

Al-Achi also explains that, while more detailed studies need to be conducted to evaluate the safety and effectiveness of dietary supplements, the limited funding provided by the U.S. government and pharmaceutical industries limits this possibility. As a result, many clinical trials evaluating dietary supplements may be too small in size or have flawed experimental design that allows for the potential for biased results.

Also, herbal supplements are often not standardized to natural origin and source of the herb (what species of plant and manufacturer were involved in making the dietary supplement), dosage used in the trial (how much "active" ingredient was in the dietary supplement) and specific ingredients of the product being tested (the concentration of all the "inactive" ingredients in the supplement).

As a result, it may be difficult to make comparisons between clinical trials that have evaluated what is assumed to be the same dietary supplement. In addition, it may be hard to determine what dose of a supplement is required to achieve a medical response.

Consequently, the Al-Achi editorial may indicate that dietary supplement researchers may need to conduct experiments according to more appropriate experimental designs so that the results of the studies are not affected by potential biases, and manufacturers may need to standardize herbal supplements more carefully so that between-study comparisons can be made more easily.

For more information about the safety and effectiveness of dietary supplements, please visit Natural Standard's Foods, Herbs & Supplements Database.


  1. Al-Achi A. Botanical medicine: the need for better quality research. Clin Pharmacol Biopharmaceut. 2012;1:e104.
  2. Natural Standard: The Authority on Integrative Medicine.
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