Appetite, food intake, and gut hormone responses to glycomacropeptide protein ingestion in older adults: A feasibility, acceptability, and pilot study

• Published in: Appetite 2024-09, Vol.200, p.107509, Article 107509
• Main Authors: Warner, Jordan, Stocker, Rachel, Brandt, Kirsten, Crabtree, Daniel R., Ormond, Lindsey, Stevenson, Emma, Holliday, Adrian
• Format: Article
• Language: English
• Subjects: Aged; Ageing; Anorexia of ageing; Appetite - drug effects; Caseins - administration & dosage; Caseins - pharmacology; Dietary Proteins - administration & dosage; Dietary Supplements; Double-Blind Method; Eating; Energy intake; Feasibility Studies; Female; Gastrointestinal Hormones - blood; Ghrelin - blood; Glucagon-Like Peptide 1 - blood; Humans; Hunger; Leucine - administration & dosage; Leucine - pharmacology; Male; Middle Aged; Peptide Fragments - blood; Peptide YY - blood; Pilot Projects; Satiation - drug effects; Satiety; Undernutrition; Whey Proteins - administration & dosage; Whey Proteins - pharmacology
• ISSN: 0195-6663; 1095-8304; 1095-8304
• DOI: 10.1016/j.appet.2024.107509

Glycomacropeptide (GMP) has a unique amino acid profile which may make less satiating than other dietary proteins. This study assessed the feasibility and likely acceptability of a leucine-enriched GMP drink and determined appetite response in older adults (OA). Thirteen OA (11f; 70 ± 4 years) were recruited for sensory assessments of a leucine-enriched GMP drink when mixed with water and with fruit smoothie, compared with whey protein isolate (WHEY). Participants also partook in a single focus group exploring acceptability to protein and supplementation. Separately, a counterbalanced, double-blind study with twelve OA (8f; 69 ± 3 years) was conducted to determine appetite and gut hormone responses. Fasting subjective appetite was recorded using visual analogue scales and a fasted venous blood sample was collected (to measures acyl-ghrelin, PYY, GLP-1, and CCK) before participants consumed either: GMP protein (27g + 3g leucine, 350 mL water), WHEY (30g, 350 mL water), or water. Participants rested for 240 min, with appetite measures and blood sampling throughout. An ad libitum pasta-based meal was then consumed. Sensory testing revealed low pleasantness rating for GMP in water vs. WHEY (16 ± 14 vs 31 ± 24, p = 0.016). GMP addition to smoothie reduced pleasantness (26 ± 21 vs. 61 ± 29, p = 0.009) and worsened the aroma (46 ± 15 vs. 69 ± 28, p = 0.014). The focus group revealed uncertainty of protein needs and a scepticism of supplements, with preference for food. Gut hormone response did not differ between GMP and WHEY (nAUC for all gut hormones p > 0.05). There was no difference between conditions for lunch ad libitum intake (549 ± 171 kcal, 512 ± 238 kcal, 460 ± 199 kcal for GMP, WHEY, and water, p = 0.175), or for subjective appetite response. Leucine-enriched GMP was not less satiating than WHEY, and low palatability and scepticism of supplements question the likely acceptability of GMP supplementation. Providing trusted nutritional advice and food enrichment/fortification may be preferred strategies for increasing protein intake in OA.