This guide, by a physician specializing in family medicine, covers almost every substance likely to be taken by mouth, and some unlikely ones. Introductory advice on the dietary supplements gives common-sense principles of nutrition. The substances are listed alphabetically in easy-to-read charts that include information on reasons to take or not to take, toxicity, laboratory tests, and interaction with other substances. The section on medicinal herbs is almost too comprehensive, including some that are dangerously toxic (although a toxicity chart follows). A useful final chart lists brand names for substances covered. The Merck Index is as complete, but is not for the lay reader. Recommended for public libraries.Eleanor Maass, Maass Assocs., New Milford, Pa.