Rationale: Protein from plant-based foods may be unable to stimulate protein synthesis due to a suboptimal essential amino acid content and a lower digestibility. However, a more optimal amino acid profile may be achieved by increasing portions sizes and blending multiple plant-based sources. Studies investigating the anabolic properties of vegan diets (total elimination of animal-based foods) rather than single plant-based foods in older adults are scarce. It remains unknown if a vegan diet can also affect protein synthesis rates in other musculoskeletal tissues than muscle.
Primary objective: To assess the effects of a 2-week preoperative vegan diet in comparison to an omnivorous diet on protein synthesis rates in Hoffa's fat pad, synovium, tendon, bone, ligaments, menisci, and cartilage in older adults with knee osteoarthritis undergoing total knee arthroplasty.
Secondary objective: To assess the effects of a 2-week preoperative vegan diet in comparison to an omnivorous diet on blood pressure and plasma amino acids in older adults with knee osteoarthritis undergoing total knee arthroplasty.
Study design: Multi-center, randomized, controlled trial with an intervention and a control group.
Study population: 40 older adults (60 - 80 years) with osteoarthritis of the knee undergoing total knee replacement.
Intervention: Controlled vegan diet versus controlled omnivorous diet, for a duration of 14 days.
Main study parameters/endpoints: Primary study parameters are protein synthesis rates of Hoffa's fat pad, synovium, tendon, bone, ligament, menisci, and cartilage. Secondary parameters include blood pressure and plasma amino acids.
Written informed consent;
Patients scheduled for total knee arthroplasty;
BMI between 20-32 kg/m2;
Aged 60 - 80 years;
Following a vegetarian or vegan diet or a diet that affects protein intake during the six months prior to the study;
Participating in a structured progressive exercise training program in the past three months;
Lost more than 4 kg body weight during three months prior to the study;
Chronic use of medications that affect protein metabolism (i.e. systemic corticosteroids, or prescription strength acne medications);
Parallel
Vegan diet
Dietary supplementVegan diet for 2 weeks before surgery
Omnivorous diet
Dietary supplementOmnivorous diet for 2 weeks before surgery
Change in tissue-specific protein synthesis rates
Tissue-specific protein synthesis rates in the knee using D2O dosing methodology
Change in blood pressure
Blood pressure measurement using an CE-certified ambulatory blood pressure monitor
Change in plasma amino acids
Difference in circulating concentrations between the two diets. In addition, it will be investigated if plasma amino acids can be used as a marker for dietary intake.
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