Dietary supplements (DS) are products designed to complement the diet, containing vitamins, minerals, or other substances. They can be marketed without evidence-based proof of their effectiveness or clinical safety. In Switzerland, nearly a third of the population uses them for various reasons, including maintaining or improving health. This article reviews the available scientific evidence on the benefits of DS for cardiovascular diseases, cancer, mortality, immunity, physical and cognitive performance. Study results are sometimes mixed, but it seems that health benefits of DS are quite limited, if not nonexistent, and routine use cannot be recommended in healthy adults.