A dietary supplement, also known as a food supplement or nutritional supplement, is a preparation intended to supplement the diet and provide nutrients, such as vitamins, minerals, fiber, fatty acids, or amino acids. A health functional food is a food where one or more new ingredients have been added to a food and the new product has an additional function. Physicians and patients need information on current evidence on the efficacy and safety of selected dietary supplements that are commonly used. The current evidence on the efficacy and safety of selected dietary supplements (beta-carotene, vitamin C, D, E, calcium, selenium, omega 3, ginseng, glucosamine, chlorella, saw palmetto, gingko, gamma linolenic acid, echinacea) for specific conditions is assessed by an evidence-based approach. With an increase in income and the aging of the population, spending on dietary supplements is steadily increasing, but concern about the safety and efficacy of dietary supplements may be relatively low. Recently, many domestic and international clinical trials on nutritional supplements have been performed. As a result, the evidence on the efficacy and safety of dietary supplements may be changed or recommendations may also be changed. Greater efforts should be made to acquire the latest knowledge about dietary supplements.