The purpose of this book is to provide an overview of dietary supplements including their definition according to the Dietary Supplement Health and Education Act, how they are manufactured and regulated, what forms they are sold in, and what the most popular products are. In discussing the most popular products people use, an effort is made to provide information on the background or origin of each ingredient. In addition, the potential mechanism of action and the clinical evidence that may exist demonstrating the efficacy or lack thereof is reviewed. This book is important given the fact that the sale and use of dietary supplements is a controversial issue. The media frequently broadcasts negative stories about the dietary supplement industry and its products and elicit the testimonies of individuals without expertise in the industry, or the science behind dietary supplements. Furthermore, the supplement industry is rife with unscrupulous fly-by-night companies that make false and misleading claims about their products, further damaging the perception of the industry. If that were all there was to the story, there would be no need for this book. On the contrary, epidemiological data demonstrates that the proper use of dietary supplements could save thousands of lives and billions of dollars in health care costs. This book is an attempt to contribute an objective perspective on the matter.