Drug and foodstuff interactions exert a critical influence on the effectiveness of therapies. Drugs may influence appetite behavior and impair the sense of taste. The degree of interactions is defined by various factors pertaining to drugs, foodstuffs and patient specificity, relating to pharmacokinetics, pharmacodynamics, and bioavailability. In that context, the Cytochrome-P450 system is of crucial importance. Therapy may be jeopardized in particular by consumption of grapefruit, dairy products, alcohol, tyramine-containing food, goji berries, and caffeine containing drinks. With therapeutic safety in mind, interactions between drugs and foodstuffs need to be painstakingly monitored. Therefore, doctors should provide their patients with individualized and practically relevant recommendations regarding medication intake.