Optimal nutrition is an important prerequisite for a top-level performance in sports. Of primary importance in this connection is the bioavailability of carbohydrates and fats as a source of energy so that the muscles can produce ATP. The amount of glycogen in the liver and skeletal muscles and possibly the intramuscular triglyceride levels play a pivotal role in this process. Gradually decreasing the amount of training during the last 6-7 days before an important game and simultaneously increasing the amount of dietary carbohydrates results in a higher physical performance. Studies have shown that carbohydrate-electrolyte solutions with 6-8% carbohydrate by weight and an osmolarity of 250-350 mosmol/l result in a maximal carbohydrate oxidation from the solution of about 1.0-1.1 g/min and a significantly enhanced endurance. A combination of carbohydrates and proteins or amino acids has proven to be very effective to accelerate recovery after exhausting exercise. Functional food ingredients such as caffeine and creatine result in a significantly enhanced performance. This is contrast to many other ingredients and products for which the extravagant claims have not been substantiated. Hence, in addition to a few functional sports supplements for which the value has been scientifically demonstrated, sound nutrition remains an absolute prerequisite for an optimal performance in sports.