Egg White Protein Meals Induce Greater Satiety and Plasma Amino Acids Compared to Wheat Gluten Protein Meals
Kristy Du FASEB 2017
While dietary protein is known to induce greater satiety than fats and carbohydrates, the extent to which the source of protein matters and the mechanisms involved are less certain. This study examined the effect of the level and source of protein on subsequent food intake, metabolism, and changes in plasma amino acids in adult Sprague-Dawley rats. Rats were entrained to a meal-feeding schedule consisting of a 30-minute treatment meal, equivalent to 10–20% of average daily intake, one hour into the dark phase followed by ad libitum access to a control diet for 5.5 hours later in the dark phase. Treatments were 1) 20% wheat gluten, 2) 35% wheat gluten, 3) 20% egg white, and 4) 35% egg white and provided in a randomized crossover design. Energy expenditure and food intake patterns were measured using indirect calorimetry housing system. Rats provided meals containing egg white protein had decreased food intake at the subsequent meal compared to wheat gluten fed rats, regardless of protein level (P<0.005). While energy expenditure did not differ among treatments, respiratory exchange ratio following ingestion of the 35% egg white protein meal was lower than the other treatment meals for several hours following ingestion (P<0.001). In a separate cohort of rats, blood plasma was collected at 30 minute intervals for 2 hours following ingestion of the treatment meals. Analysis of plasma amino acid concentrations revealed greater increases in measured amino acids following ingestion of meals containing egg white protein. Specifically, concentrations of valine and lysine were the largest contributors to the difference observed in plasma amino acids.
Overall, these results suggest protein-induced satiety depends on the protein source. Egg white protein caused greater satiety than wheat gluten protein, corresponding to greater postprandial increases of plasma amino acids. These results collectively highlight the importance of the consideration of protein sources as it relates to controlling appetite.