FIGURE 1.

A framework for the categorization of different protein forms, taken from the most basic level through increasing levels of nutritional complexity (greater energy content, macro- and micronutrient density, complex food matrices, bioactive peptides, etc.). With increasing nutritional complexity plasma leucine appears to become less predictive of postprandial muscle protein synthesis rates, and seemingly other leucine-independent factors become more prominent in regulating the anabolic response to feeding.