This invention relates to a method of increasing a feeling of a) energy or b) cognitive functions, selected from the group consisting of: sustained attention, faster reaction times, and information processing; or c) quality of sleep; or d) feelings of well-being and happiness in a healthy adult using a dosage form comprising a low dose of a Trp-containing di- and/or tri-peptide mixture characterized in that the peptide composition is an egg iysozyme hydroiysate with a Trp/LNAA ratio greater than 0,15 and which provides IQ-to 100 mg Trp per dose. This dosage form can be administered acutely or can be administered multiple times per day for an extended period of time.