This book provides an overview of dietary supplements including their definition, how they are manufactured and regulated, what forms they are sold in, and what the most popular products are. An effort is made to provide relevant information on the background, mechanism of action, and the clinical evidence demonstrating their efficacy or lack thereof. This book is important given the popularity of dietary supplements and the controversies around their sale and use. Negative portrayal of the industry by the media, and unscrupulous companies that make false and misleading claims about their products, fuel the controversy. At the same time, 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.