The Effect of a 2-week Preoperative Vegan Diet Versus Omnivorous Diet on the Protein Turnover in the Osteoarthritic Knee

Inclusion Criteria:

• Written informed consent;

• Patients scheduled for total knee arthroplasty;

• BMI between 20-32 kg/m2;

• Aged 60 - 80 years;

• Mentally competent, as judged by the treating physician;

Exclusion Criteria:

• Following a vegetarian or vegan diet or a diet that affects protein intake duringthe six months prior to the study;

• Participating in a structured progressive exercise training program in the pastthree 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. systemiccorticosteroids, or prescription strength acne medications);

• Being diagnosed with one of the following: diabetes mellitus, rheumatoid arthritis,peripheral artery disease Fontaine III or IV, COPD GOLD III or IV, neoadjuvantchemotherapy or radiotherapy, phenylketonuria, collagen disorders (e.g. Marfan andEhler-Danlos);

• Alcohol abuse;

• Surgical intervention to the knee in the past four weeks;

• Total parenteral nutrition at day of surgery;

• Glomerular filtration rate (GFR) <20 mL/min/1.73 m2;

• Allergic or intolerant to any product included in the diets;

• Osteoarthritis of the knee secondary to septic arthritis, osteonecrosis, fracture,osteochondritis dissecans, or malignant processes;

• Any other medical condition that may interfere with the safety of the participantsor the outcome parameters, in the investigators judgement;

• Not willing to stop nutritional supplements, with the exception of vitamin D andsupplements on medical advice.

• Investigator's uncertainty about the willingness or ability of the participant tocomply with the protocol instructions;

• Participation in other studies that may have an impact on the outcomes during thethree months before the start of the current study.