Studies have been rather inconclusive regarding the effect of protein on dietary intake and appetite. Until recently the effect of dietary protein on the level of free essential amino acids in brain and on serotonin levels has been the focus of these studies.1-7 In a review of these studies8 the authors concluded that analysis of evidence of associations among dietary protein content, brain amino acid and serotonin concentrations, and protein self-selection by rats suggests that:

1. Protein intake is not regulated precisely, although rats will select between low-and highprotein diets to obtain an adequate, but not excessive, amount of protein.