Comparing absorption of protein from high-protein fermented and non-fermented foods in older adults

What is the intervention: • Soybeans: 71 g of raw soybeans (~180 g cooked), providing ~2 g of leucine, will be soaked overnight, boiled, and frozen in pre-weighed portions to ensure consistency across participants. On the day of testing, portions will be reheated (via microwave) to serving temperature. • Beef: 139 g of raw beef (minced, 10% fat), providing ~2 g of leucine, will be portioned into patties and frozen before being pan-cooked fresh each test day, using standardised cooking method (dry pan, no added oil), weighed before and after cooking to track moisture loss. • Tempeh: 143 g of raw, commercially prepared tempeh, from the company Primasoy, will be steamed for 10 minutes before serving • Natto: 164g of raw, frozen, commercially prepared Natto (from the company Dai’s Natto) will be thawed overnight prior to the test day, stirred and served immediately. Each meal will be provided alongside 5 mL of soy sauce that can be added optionally by the participants for flavour. Any uneaten food will be weighed to correct the ingested leucine dose. Who delivers it and their relevant expertise: Test meals will be prepared and administered by the study team under the supervision of Chief Investigator (Senior Lecturer in Nutrition and Dietetics, La Trobe University; APD; PhD in Nutrition; expertise in whole-food protein interventions, musculoskeletal health, and clinical trial coordination). Blood sampling will be performed by a registered nurse along with experienced researchers from Swinburne and La Trobe Universities. Expertise in food safety and nutritional analysis of food products will also be delivered by APDs from Swinburne and La Trobe Universities. A PhD student will coordinate day-to-day study activities. How it is delivered: face to face and will be in groups of a maximum of 2 How often and for how long: 4 sessions (about 6.5 Hours each- each delivering a different intervention of either soy beans, tempeh, natto and beef) and one screening visit (60 minutes) prior to commencement of the 4 sessions. Each of the 4 interventions (soy beans, tempeh, natto and beef) will only be served once. there is a washout period that will be 1 week inbetween each session. Where it is delivered: Metabolic lab (venous blood sampling room) and food-safe kitchen at La Trobe University, Melbourne, Australia. Adherence: • Written study day checklist will be given at screening, covering the 2-day diet prior to the test-days, alcohol and exercise restrictions and the overnight fast. • They will receive an email 48 hours before each visit repeating the key instructions in plain language. • They will be provided with a standardised evening meal prior to the testing days that they are to eat prior to 10pm. • Participants will be provided with a printed version of their 2-day diet diary after they have recorded it before the first test day, and asked to tick off each item as it is consumed for each of the 2-day periods prior to each subsequent test day. • Verbal checklists on testing days will be used to confirm no strenuous exercise, alcohol or medication deviations. • Test meals will be served under staff supervision, and monitored for complete consumption. • Researchers will remind participants to complete each VAS at the allocated time points. • Participants will remain in a comfortable lounge area throughout the testing period. • Participants will receive a reminder card for their next visit upon completion of each visit. • Participants will be provided with a $250 voucher upon completing the study (or a pro-rata amount depending on number of testing days completed) to reimburse them for their time and travel.