Investigating the effects of cow, goat or sheep milk on nutrition and digestive comfort in older women

The intervention will consist of two servings of cow, goat, or sheep milk powder per day for 12 weeks (40 people in each group). The milk powder will be made up with water to mimic the nutritional content of fresh milk: 40 g cow milk powder with 160 mL water; 35 g sheep milk powder with 215 mL water; 30 g goat milk powder with 200 mL water. The drinks will be consumed with breakfast and lunch. The study duration is a nominal total of 14 weeks, with a 2-week lead-in phase and 12-week intervention phase. During the 2-week lead-in phase (and throughout the duration of the intervention), participants will record their bowel habits every day, on an app designed for this study, and will complete weekly questionnaires about their digestive symptoms, mood (anxiety, depression), and sleep quality using validated questionnaires. On the 2nd week of the lead-in phase, participants will complete a non-consecutive 3-day diet, wear an actigraphy accelerometer for 7-days to measure activity levels, and undergo a Dual-energy X-ray Absorptiometry (DXA) scan to measure body composition. The day before their baseline visit, participants will collect a faecal sample, and will fast overnight for 9 hours. At the baseline clinic (beginning of the intervention phase), participants will provide a blood sample, have height, weight and waist circumference measured, and undergo functional tests (hand grip strength and a walk test). They will also complete a set of questionnaires about their mental health. At the clinic, a sub-group of participants from each milk group will consume double the amount of the milk powder that they have been assigned (80 g cow milk powder; 70 g sheep milk powder; 60 g goat milk powder). The powders will be made up to 350 mL with water. The participants will consume the milk within 10 minutes. After finishing the milk, they will provide blood samples hourly over 5-hours. During this time they will complete questionnaires on digestive comfort and appetite. This sub-group assessment will be undertaken once at baseline and again at follow-up (week 12). The double-amount of powder consumed during the clinic will replace the participant's regular intervention (two daily serves of milk powder with breakfast and lunch) for the first and last days of the intervention period. The first 25 people in each group who consent to participating in the sub study will be enrolled. Participants will be given four weeks supply of milk powder to take home. At weeks 4 and 8, participants will return any unused milk powder, and be provided with their next 4-week supply. Compliance will be monitored by checklist, and by weighing left-over milk powder. Participants will also have their waist circumference and body weight measured at the clinics. At the final follow-up visit, participants will repeat all of the aforementioned baseline visit procedures. The week prior to their follow-up visit, they will complete the same set of questionnaires, 3-day diet record, actigraphy, DXA scan, and collect a faecal sample. At the follow-up clinic visit, they will have their weight and waist circumference measured, and provide a fasted blood sample. The participants in the sub study will provide blood samples before and hourly, up to 5 hours, after consuming their milk. All participants will receive their reimbursement ($200 grocery voucher). Attendance of clinic visits and completion of questionnaires and study tests (accelerometery, DXA, functional tests, blood tests) will be assessed to measure the adherence of participants.