Muscle Protein Synthesis in Response to Plant-Based Protein Isolates With and Without Added Leucine Versus Whey Protein in Young Men and Women.

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-[ringC] 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 ( < 0.001). However, MPS increase following ingestion of PBP was less than that following ingestion of PBP + Leu ( = 0.002) and WHEY ( = 0.046). There were no differences in MPS between PBP + Leu and WHEY ( = 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.