Reinhardt obtained his undergraduate degree from Rutgers University, majoring in Chemistry and Pre-Med. Following five years in graduate school studying biochemistry and microbiology, also at Rutgers, he served as a Captain in the U.S. Army Medical Research and Development Command at the Letterman Army Institute of Research in San Francisco. As a military scientist, Reinhardt directed a multidisciplinary research program investigating tropical infectious diseases in military personnel. He and his colleagues at the Letterman Army Institute of Research were awarded the American Academy of Dermatology's Gold Medal Award for Original Research in 1972 for defining the roles of nutrition and stress on the immune system and susceptibility to skin diseases in Vietnam.

While operating a clinical practice in northern California, Reinhardt consulted with amateur and professional athletes and participated in several environmental legal cases involving spills of toxic chemicals. In 1984, Reinhardt co-founded the National Coalition to Stop Food Irradiation, and subsequently testified at FDA Hearings on the design and implementation of the current food label for nutrition content of packaged foods. As the founding Director of People for Pure Foods, he has lobbied Congress people in Washington and participated in the 'Grass Roots' efforts to envision the need for and then pass the Dietary Supplement and Health Education Act of 1994 (DSHEA).