Impact of Vegan Diets on Resistance Exercise-Mediated Myofibrillar Protein Synthesis in Healthy Young Males and Females: A Randomized Controlled Trial

Background: Protein ingestion stimulates muscle protein synthesis rates (MPS) to support the turnover of skeletal muscle protein mass. However, dietary patterns consist of a variety of protein foods with different amino acid compositions consumed at multiple meal-times throughout the day. Omnivorous (OMN) and vegan (VGN) dietary patterns may differentially stimulate MPS. Moreover, the distribution and frequency of protein intake may also play an important anabolic regulatory role.

Objective: We aimed to determine the effect of OMN and VGN dietary patterns and protein distribution (balanced [B] and unbalanced [UB]) in regulating changes in daily myofibrillar protein synthesis rates during a 9-d resistance training intervention.

Design: Forty healthy, physically-active males and females (28 M, 12 F; 25 ± 4 y; BMI = 24.1 ± 2.1 kg·m-2) consumed a weight-maintenance diet providing 1.1–1.2 g·kg-1·d-1 of dietary protein from an OMN or VGN dietary pattern with UB (10, 30, 60% of daily protein at meal 1, 2, and 3, respectively) or B (20% of daily protein at 5 eating occasions) distribution. Participants completed whole-body resistance exercise three times during the controlled feeding trial while consuming deuterated water (D2O) for the measurement of daily myofibrillar protein synthesis rates.

Results: The %kcals from carbohydrate was higher (P = 0.045) in the OMN compared to VGN groups, but no other differences in dietary intakes were observed. Myofibrillar protein synthesis rates did not differ between OMN-UB (3.04 ± 1.85%·d-1), OMN-B (2.43 ± 1.21%·d-1), VGN-UB (2.52 ± 1.77%·d-1), and VGN-B (2.49 ± 1.56%·d-1) groups (all P > 0.05).

Conclusions: Our results demonstrated that the anabolic action of animal vs. vegan dietary patterns are similar. Moreover, there is no regulatory influence of distribution between the two dietary patterns on the stimulation of myofibrillar protein synthesis rates in young adults. This trial was registered with ClinicalTrials.gov (NCT04232254).