In their current review, Weijs and colleagues highlight the importance of protein and amino acid provision for improving clinical outcome in critically ill patients. The interdependence between energy and protein is highlighted. They call for urgent research to develop new methods to evaluate protein and amino acid requirements, accurately and conveniently, in order to optimize nutrition support for critically ill patients. Appropriate nutrition delivery for critically ill patients remains a highly debated issue. Energy, a critical factor for life, was until now the superstar of nutrition support. It now faces a rival or, more correctly, a partner in function, namely protein. This is a chance to take a close look at protein, the new hero in the field of critical care nutrition, and the struggles it encounters in becoming the true superstar.