A Well-Balanced Vegan Diet Does not Compromise Daily Mixed Muscle Protein Synthesis Rates when Compared with an Omnivorous Diet in Active Older Adults: A Randomized Controlled Cross-Over Trial

Background: Plant-based foods have reduced protein digestibility and frequently display unbalanced amino acid profiles. Plant-based foods are therefore considered inferior to animal-based foods in their anabolic potential. No study has assessed the anabolic potential of a vegan diet that provides a large variety of plant-based protein sources in older adults. Objectives: To investigate the effect of a 10-d vegan diet on daily mixed muscle protein synthesis (MPS) rates in comparison with an isocaloric, isonitrogenous, omnivorous diet in community-dwelling older adults. Methods: This cross-over trial assessed 34 community-dwelling older adults (72 +/- 4 y, 18 males, 16 females), who were randomly assigned to consume a 10-d controlled vegan diet, followed by a controlled omnivorous diet (60% animal protein), or vice versa. One day before the study diets, participants consumed 400 mL deuterated water, followed by daily doses of 50 mL. Subsequent plasma and muscle samples were collected during the intervention period. Physical activity levels were assessed using accelerometry. Secondary outcomes were cardiometabolic risk factors and appetite. Statistical analyses were performed using linear mixed models, and results are presented as means + standard errors. Results: Integrated MPS rates did not differ between the vegan (1.23 +/- 0.04%/d) and omnivorous (1.29 +/- 0.04%/d) diets (P = 0.2542). Plasma low-density lipoprotein (Delta 0.23 +/- 0.03, P < 0.0001), high-density lipoprotein (Delta 0.03 +/- 0.14, P = 0.0387), and total cholesterol (Delta 0.25 +/- 0.04, P < 0.0001) levels were significantly lower succeeding the vegan diet than the omnivorous diet. There were no significant differences between the omnivorous and the vegan diet in fasting plasma triglyceride, glucose and insulin levels, homeostasis model assessment of insulin resistance, and systolic and diastolic blood pressure (P > 0.05). Physical activity levels were high (12,460 +/- 4512 steps/d). Conclusions: A well-balanced vegan diet providing a variety of plant-based protein sources does not compromise daily MPS rates when compared with an isocaloric, isonitrogenous omnivorous diet in physically active, older adults.