A modest but very sound book on vitamins, their function, metabolism, and the deficiency diseases which may develop -- albeit usually in mild form -- from insufficient intake or impaired utilization. Di Cyan writes of vitamins for health -- not of the ongoing experiments in nutrition and disease (cancer, arthritis, schizophrenia -- research which is so far inconclusive). He does not recommend swallowing fistfuls of supplements from the health food store or treating your headaches, acne or tension with self-prescribed vitamin therapies. He does come out four-square in support of Linus Pauling's use of vitamin C as treatment for the common cold. Every vitamin, A through K, is discussed separately as are the micronutrients or trace minerals -- zinc, magnesium (its lack may be the cause of crib deaths), iron, copper. Di Cyan warns against deficiencies induced by ""organic,"" vegetarian or other tad diets and notes that ethnic cuisines, poverty, stress, alcoholism and pregnancy are all likely to produce imbalances. He is leery of too much extrapolation from animal studies (""only specific observations in man apply to man""). One final point: the vitamin levels of foods vary -- milk has twice as much vitamin A in summer as winter and eight times as much E in fall than spring. A down to earth, balanced overview in a day when the most extravagant claims are being bandied about.