Micronutrient supplements: toxicity and drug interactions.

Self-prescribed use of single micronutrients in excessive or pharmacologic dosage, without professional medical supervision, is on the increase. This raises potential problems of chronic toxicity and adverse interactions with prescribed and over-the-counter drugs. These questions are of special concern in the elderly, who utilize micronutrient supplements the most and at the same time have the greatest incidence of chronic illness and take the largest amount and variety of drugs. This review examines the toxicity and drug interactions of the thirteen vitamins and the trace elements chromium, selenium, and zinc.