Evidence of Enhanced Serum Amino Acid Profile but Not Appetite Suppression by Dietary Glycomacropeptide (GMP): A Comparison of Dairy Whey Proteins

Abstract

Objective: There is evidence that high-protein foods increase satiety and may aid weight loss, yet little is known of differential effects of protein composition. The aim of the study was to compare the acute effects of 4 whey proteins on satiety and food intake and to evaluate possible relationships with postprandial serum amino acid concentrations.

Methods: Isoenergetic high-protein shakes (∼1 MJ) containing 25 g whey protein were given to 18 lean male participants using a crossover design. Three protein fractions identified as satiating in a rat model, glycomacropeptide (GMP), beta-lactoglobulin (ß-lac), and colostrum whey protein concentrate (WPC), were compared with a WPC control. A standardized 2.5MJ breakfast was given at 0830 hours, followed by the preload beverages at 1130 hours. Participants rated appetite sensations using visual analogue scales (VAS) prior to the beverage (baseline, 0 minutes) and then at 15, 30, 45, 60, 90, 150, and 210 minutes. Energy and macronutrient intake was measured by covert weighing of an ad libitum lunch meal at 90 minutes. Repeat blood samples were collected via venous cannulation.

Results: Serum amino acid (a.a.) concentrations differed between whey fractions (p = 0.012) and were higher following GMP compared to ß-lac (p = 0.051) and colostrum WPC (p = 0.044) but not the WPC control (p = 0.20). There was no difference in VAS-rated hunger, satisfaction, or thoughts of food between whey fractions, but fullness did differ (p = 0.032) and was highest following the ß-lac beverage. Energy intake was not suppressed relative to control by any of the 3 whey fractions.

Conclusions: We conclude that total serum a.a. concentration was a poor indicator of satiety, with little evidence of differential satiety between these whey proteins other than a modest enhancement of fullness by ß-lac.

Key words:

• satiety
• ad libitum intake
• serum amino acids
• dairy whey protein
• GMP
• beta-lactoglobulin
• colostrum whey protein

ACKNOWLEDGMENTS

LactoPharma New Zealand provided the funding for this trial. Fonterra Co-operative Group, New Zealand, supplied the protein beverages. We thank Shelley Baty for preparation of the study diets, Nisha Patel and Midi Tsai for technical assistance in conducting the study, and Martin Middleditch for analysis of the serum amino acid concentrations. We also thank the participants in this intervention trial.

Disclosures: LactoPharma New Zealand provided the funding for this trial. Fonterra Co-operative Group, New Zealand, supplied the whey protein beverages. R.S.H. was an employee of Fonterra Co-Operative Group.