None listed
Conditions
Brief summary
In older adults, insufficient protein intake facilitates muscle loss by limiting muscle anabolism. Furthermore, older people may experience ‘anabolic resistance’, increasing the threshold of protein required to stimulate postprandial protein anabolism (>25-30g). Importantly, providing that sufficient protein is ingested, ageing does not impair the capacity for muscle protein synthesis. Therefore, protein-rich supplements are commonly used to manage undernutrition in older people. In younger adults, protein is known to be the most satiating macronutrient - high-protein diets are often advocated to promote weight loss. Therefore, the satiating effects of increased protein ingestion could counteract the positive effects of increased protein ingestion on lean mass in older people. Interestingly, our studies have previously shown that suppression of energy intake after intraduodenal and oral whey protein loads is less in older compared to young people, despite slower gastric emptying and increased plasma CCK and GIP concentrations in the older subjects, factors which are associated with suppression of energy intake in young people. Timing of protein supplements (i.e. 3, 2, 1 hour(s) or just before a meal) did not affect energy intake at a subsequent meal. These studies suggest that older people have impaired appetite and energy intake regulation. The lack of suppression caused an increase in overall energy and protein intake, which supports the use of ‘pure’ protein supplements in undernourished older people. The aim of the study is to characterise in healthy younger and older individuals, the effect of oral protein ingestion 30 min before breakfast, lunch and dinner on energy intake, appetite, blood glucose and plasma gut hormone concentrations (e.g. insulin, glucagon, ghrelin, CCK, GIP, GLP-1 and PYY). We hypothesise that the acute suppression of appetite and energy intake by oral whey protein is less in healthy older than younger people. To investigate this, a total of 15 healthy older men aged 65-85 years with a body mass index (BMI) of 20-30 kg/m2 and 15 healthy younger men aged 18-35 years with a BMI of 20-30 kg/m2 will be recruited. Each subject will be studied on 3 occasions. On each occasion, they will receive, in randomized fashion, a drink of flavoured water (control; ~2 kcal) or a drinks of 30 g whey protein (120 kcal) 30 min before a breakfast (~9am, t = 30). Energy intake will be assessed at breakfast (t=30), lunch (t=270) and dinner (t=510). Blood samples will be taken, antral area will be measured and visual analog scales will completed at regular time intervals. Subjects will be allowed 30 min for all meals to freely consume food until they are comfortably full.
Interventions
A total of 15 healthy, older men aged 65-85 years with a body mass index (BMI) of 20-30 kg/m2 and 15 healthy, younger men aged 18-35 years with a BMI of 20-30 kg/m2 will be recruited.
Each subject will be studied on 3 occasions, separated by at least 3 days. On each occasion, they will receive, in randomized fashion, a drink containing either zero (control) 30 or 70 g loads of whey protein. Subjects will be asked to ingest the drink within 2 minutes. The drinks will be equivolaemic (~450 mL), c
A total of 15 healthy, older men aged 65-85 years with a body mass index (BMI) of 20-30 kg/m2 and 15 healthy, younger men aged 18-35 years with a BMI of 20-30 kg/m2 will be recruited. Each subject will be studied on 3 occasions, separated by at least 3 days. On each occasion, they will receive, in randomized fashion, a drink containing either zero (control) 30 or 70 g loads of whey protein. Subjects will be asked to ingest the drink within 2 minutes. The drinks will be equivolaemic (~450 mL), controlled for osmolality and matched for taste, texture and appearance. The drinks will contain different quantities of food-grade whey protein isolate powder (Fonterra Australia Pty Ltd, Mt Waverley, Australia) dissolved in varying amounts of distilled water, sodium chloride and low-calorie lime cordial (Bickford’s ‘diet lime’ cordial). For example, the ‘control’ protein drink will contain 0 g protein, 1.2 g sodium chloride, 358.8 mL water and 90 mL cordial, ‘low protein’ load will contain 30 g of protein, 0.3 g sodium chloride, 334.7 mL water and 85 mL cordial, and the ‘high protein’ load will contain 70 g of protein, 0 g sodium chloride, 280 mL water and 100 mL cordial. The drinks will be covered all times, so the subject will be blinded for the treatment. Subjects will arrive at the laboratory ~8.00 am after fasting for ~12 hours overnight and refraining from exercise and alcohol for 24 hours. Subjects will be required to consume a standard meal the night before each study day (beef lasagne, McCain Foods Pty Ltd, Wendouree, VIC). The drink will be administered at t = 0 (~8.30am) and energy intake will be assessed at breakfast t = 30 min (~9am), lunch t = 270 min (~1pm) and dinner t = 510 min (~5pm). Breakfast and lunch will be a buffet style meal and dinner will consist of a warm standardised meal e.g. a homogenous pasta dish. The weight of the foods will be recorded before and after it is offered to the subjects and energy intake and macronutrient composition calculated. Palatability of the drinks and meals will be measured with a questionnaire. VAS questionnaires will be collected 5 min before drink consumption (baseline), 0, 15 and 30 min after drink consumption, 5 min before and 0, 15 and 30 min after consumption of breakfast, lunch and dinner. A 2D ultra sound image of the stomach will be made at baseline (t=0), and after the consumption of the drink (t= 5, 15, 30). Subjects will only be allowed to consume water in between meal times. Subjects will be supervised by the researchers to monitor compliance. We will ask the subjects to record the amount of water consumed. Subjects will be reimbursed with $15 per hour for their time spent in the laboratory.
Sponsors
Stijn Soenen
Study design
Allocation
Randomised controlled trial
Intervention model
Crossover
Primary purpose
Prevention
Masking
Blinded (masking used) (Subject)
Eligibility
Sex/Gender
Male
Age
18 Years to No maximum
Healthy volunteers
Yes
Inclusion criteria
Subjects will be required to be weight-stable (i.e. <5 % fluctuation in their body weight) at study entry, as determined by their self-reported weight in the preceding 3 months. Subjects will be asked to maintain their usual level of physical activity throughout the study.
Exclusion criteria
Each subject will be questioned prior to the study to exclude: • smokers of cigarettes/cigars/marijuana; • intake of >2 standard drinks on >5 days per week; • intake of any illicit substance; • vegetarians; • use of prescribed medications which may affect appetite, body weight, gastrointestinal function or energy metabolism (e.g. domperidone and cisapride, anticholinergic drugs (eg atropine), metoclopramide, erythromycin, hyoscine, orlistat); • use of non-prescribed medications (including vitamins and herbal supplements) which may affect appetite, body weight, gastrointestinal function or energy metabolism (e.g. green tea extracts, Astragalus, St Johns Wort etc.) - if subjects are willing to stop using vitamins and/or supplements which affect gastrointestinal or energy metabolism during the study, a washout period of at least 14 days prior to the first test day will apply; • food allergy(s), diabetes mellitus (fasting glucose >6.9 mmol/L), epilepsy, or gallbladder, pancreatic, cardiovascular or respiratory diseases; • significant gastrointestinal symptoms, disease or surgery (apart from uncomplicated appendectomy), as determined by a questionnaire; • impaired cognitive function (score <25 on Mini-Mental State Examination); • depression (a score >11 on the Geriatric Depression Questionnaire); • any other illness deemed significant by the investigator (including chronic illnesses not explicitly listed above); • low ferritin levels (<20ug/l) and plasma Hb levels (130g/l), or blood donated in the 12 weeks prior to taking part in the study, in line with current Australian Red Cross Guidelines; • individuals who are found to be unable to comprehend the study protocol. Individuals whose blood glucose or HbA1c results are above the normal range or ferritin levels are low will be informed of the test results and advised to consult their GP. A letter will also be sent to their GP to notify them of the test results.
Outcome results
None listed