Dietary supplements: important concerns for the clinician.

Review articles, clinical trials and case reports on the usage patterns of dietary supplements are commonly published in medical journals. However, clinicians must acknowledge several limitations and methodological flaws with some of the available literature. The lack of product quality control, the use of combination products, and the paucity of product bioavailability data are known weaknesses of this research. Botanical dietary supplements present additional challenges to good quality research. Many factors impact the chemical composition of plants and, thus, influence the constituents in a manufactured product. Furthermore, the use of a validated and accurate product analysis technique is imperative to research on dietary supplements. This article discusses these topics in detail with special emphasis on those issues most important to practicing clinicians.