Effects of protein on gut hormones and motility, and appetite and energy intake in undernourished compared with healthy older individuals

INTERVENTION: A single 60 minute intraduodenal infusion at 4mL/min of i) 0 kcal/min (saline control) ii) 1.5 kcal/min (Whey Protein Hydrolysate) in 12 undernourished and 12 'healthy' older subjects Appetite sensation questionnaires in the form of a Visual Analogue Scale (VAS), blood samples. A standard buffet meal will be provided at the end of the 60 minute infusion from which the volunteer has 30 minutes to eat until comfortably full. The buffet meal consists of 300ml orange juice, 600ml water, 375ml iced coffee, 4 slices white bread, 4 slices brown bread, 100g deli leg ham, 100g virginian chicken, 4 slices cheese, 100g tomato, 100g cucumber, 100g lettuce, 2 portions mayonnaise, 2 portions margarine, 1 medium apple, 1 medium banana, 200g chocolate custard, 150g fruit salad, 200g strawberry yoghurt, and a 14g milky way bar. Each volunteer will receive one of each infusion solution over 2 study days. Study visits will be seperated by no less than 3 days. Each study visit will last approximately 3‐6 hours. CONDITION: Malnutrition in older people PRIMARY OUTCOME: Antropyloroduodenal motility (antropyloroduodenal pressures; number of antral, duodenal and isolated pyloric pressure waves; basal pyloric pressure) assessed by Manometry. Macronutrient and total energy intake of standard buffet meal are determined using Foodworks Software. Plasma concentrations of gut hormones (cholecyctokinin (CKK), glucagon‐like peptide‐1 (GLP‐1), peptide YY (PYY), gastric inhibitory polypeptide (GIP), ghrelin, glucagon and insulin), glucose and amino acids. SECONDARY OUTCOME: Appetite sensations using a Visual Analogue Scale (VAS) (nausea, hunger, fullness, desire to eat, thirst). Blood pressure and heart rate are determined using an automatic sphygmomanometer. INCLUSION CRITERIA: Undernourished older people: at risk of malnourishment + malnourishment defined by a well validated, widely used, screening tool that is associated with poor outcomes in older people: the Mini Nutritional Assessment (MNA) with a score <24 out of 30 and, at least one of: self‐reported weight loss in the previous 3 months, or a Body Mass Index (BMI) <22 kg/m2 'Healthy' older people: BMI: 20‐30 kg/m2 Weight stable (<5% fluctuation in body weight in previous 3 months).