Acute Microbial Protease Supplementation Increases Net Postprandial Plasma Amino Acid Concentrations After Pea Protein Ingestion in Healthy Adults: A Randomized, Double-Blind, Placebo-Controlled Trial

Abstract

Background: Digestibility is a primary factor in determining the quality of dietary protein. Microbial protease supplementation may be a strategy for improving protein digestion and subsequent postprandial plasma amino acid availability.

Objectives: To assess the effect of co-ingesting a microbial protease mixture with pea protein on postprandial plasma amino acid concentrations.

Design: A mixture of 3 microbial protease preparations (P3) was tested for proteolytic efficacy in an in vitro static simulation of gastrointestinal digestion. Subsequently, in a randomized, double-blind, placebo-controlled crossover trial, 24 healthy adults (27 ± 4 y; 12 females, 12 males) ingested 25 g pea protein isolate (20 g protein, 2.2 g fat) with either P3 or maltodextrin placebo (PLA). Blood samples were collected at baseline and throughout a 0‒5 h postprandial period and both the early (0-2 h) iAUC and total (0-5 h) iAUC were examined.

Results: Plasma glucose concentrations decreased in both conditions (P < 0.001), with higher concentrations after P3 ingestion compared with PLA (P < 0.001). Plasma insulin concentrations increased for both conditions (P < 0.001) with no difference between conditions (P = 0.331). Plasma total amino acid (TAA) concentrations increased over time (P < 0.001) with higher concentrations observed for P3 compared with PLA (P = 0.010) during the 0‒5 h period. There was a trend for elevated essential amino acid (EAA) concentrations for P3 compared with PLA (P = 0.099) during the 0‒5 h postprandial period but not for leucine (P = 0.282) or branched-chain amino acids (BCAA, P = 0.410). The early net exposure (0‒2 h iAUC) to amino acids (leucine, BCAA, EAA, and TAA) was higher for P3 compared with PLA (all, P < 0.05).

Conclusions: Microbial protease co-ingestion increases plasma TAA concentrations (0-5 h) and leucine, BCAA, EAA, and TAA availability in the early postprandial period (0‒2 h) compared with ingesting pea protein with placebo in healthy adults.

Keywords: anabolism; leucine; plant-based protein; protein foods.

FIGURE 1

Schematic of the experimental design for the clinical trial in this randomized, double-blind, placebo-controlled crossover study. GI, gastrointestinal; P3, mixture of 3 microbial protease preparations; PLA, placebo; VAS, visual analog scale.

FIGURE 2

Self-reported feelings of hunger (A), fullness (B), and desire to eat (C) during the postabsorptive and postprandial period. Ingestion of the mixture of 3 microbial protease preparations (P3; n = 24) or placebo (PLA; n = 24) is denoted by the vertical dotted line. Values are means ± SD. ∗Denotes significant difference from baseline (t = –5); #Denotes significant difference from immediately post-ingestion of P3 or PLA (t = 0). †Denotes significant main effect of condition (P < 0.05).

FIGURE 3

Plasma glucose (A) and insulin (B) concentrations during the postabsorptive and postprandial period. Insets show the incremental area under the curve (iAUC) over the entire (0‒5 h) postprandial period. Ingestion of the mixture of 3 microbial protease preparations (P3; n = 24) or placebo (PLA; n = 24) is denoted by the vertical dotted line. Values are means ± SD. ∗Denotes significant difference from baseline (t = –5; P < 0.05). †Denotes significant main effect of condition (P < 0.05).

FIGURE 4

Plasma total amino acid concentrations during the postabsorptive and postprandial period. Insets show the incremental area under the curve (iAUC) over the early (0‒2 h) and total (0‒5 h) postprandial periods. Ingestion of the mixture of 3 microbial protease preparations (P3; n = 24) or placebo (PLA; n = 24) is denoted by a vertical dotted line. Values are means ± SD. ∗Denotes significant difference from baseline (t = –5; P < 0.05); †Denotes significant difference between conditions (P < 0.05).

FIGURE 5

Plasma essential amino acid (A), BCAA (B), and leucine (C) concentrations during the postabsorptive and postprandial periods. Insets show the incremental area under the curve (iAUC) over the early (0‒2 h) postprandial period. Ingestion of the mixture of 3 microbial protease preparations (P3; n = 24) or placebo (PLA; n = 24) is denoted by the vertical dotted line. Values are means ± SD. ∗Denotes significant difference from baseline (t = –5; P < 0.05); †Denotes significant difference between conditions (P < 0.05).