Muscle Protein Synthesis in Response to Plant-Based Protein Isolates With and Without Added Leucine Versus Whey Protein in Young Men and Women
Changhyun Lim, Tom A.H. Janssen, Brad S. Currier, Nelani Paramanantharajah, James McKendry, Sidney Abou Sawan, Stuart M. Phillips
Abstract
Background Plant-based protein supplements often contain lower amounts of leucine and other essential amino acids (EAAs), potentially making them less effective in stimulating muscle protein synthesis (MPS) than animal-based proteins. Combining plant proteins could improve the EAA profile and more effectively support MPS. Objectives The aim of this study was to determine the effect of a novel plant-based blend protein (PBP), PBP with added leucine (PBP + Leu) to levels equivalent to whey protein isolate (WHEY) on aminoacidemia and MPS responses in young men and women. We hypothesized that PBP + Leu would stimulate MPS equivalent to WHEY, and both would be greater than PBP. Methods We employed a randomized, double-blind, crossover study consisting of 3 separate study visits to compare PBP, PBP + Leu, and WHEY. To measure MPS response to ingestion of the supplements, a primed continuous infusion of L-[ring 13 C 6 ] phenylalanine was administered for 8 h at each study visit. Skeletal muscle tissue and blood samples were collected to measure aminoacidemia and MPS. Results All protein supplements increased mixed MPS above postabsorptive levels ( P < 0.001). However, MPS increase following ingestion of PBP was less than that following ingestion of PBP + Leu ( P = 0.002) and WHEY ( P = 0.046). There were no differences in MPS between PBP + Leu and WHEY ( P = 0.052). Conclusions Consumption of PBP isolate with added leucine stimulated MPS to a similar extent as whey protein in young men and women. PBPs containing higher leucine content promote anabolism to a similar extent as animal-based proteins. This study was registered at clinicaltrials.gov as NCT05139160.