Author(s): ALHAMWI, A., LAM, K., RUSSO, J., ABOU SAWAN, S., GARVEY, S.M., CHURCHWARD-VENNE, T.A., Institution: MCGILL UNIVERSITY, Country: CANADA, Abstract-ID: 2665

INTRODUCTION:
Dietary protein is essential for supporting growth, metabolic function, and overall health. After ingestion, protein is digested and absorbed in the gastrointestinal tract before its constituent amino acids (AA) enter systemic circulation for uptake by peripheral tissues (e.g., skeletal muscle). Biotics, (i.e., prebiotics, probiotics, postbiotics, synbiotics, and microbial enzymes), are microbe based interventions that confer a health benefit on a host. Emerging evidence suggests that biotics may enhance protein digestion and increase circulating AA concentrations. The objective of this study was to conduct a systematic review of studies evaluating the effects of biotics and protein co-ingestion on blood AA outcomes in humans.
METHODS:
This systematic review was conducted following the PRISMA guidelines and pre-registered on PROSPERO (CRD420251046023). A systematic search was conducted in 4 databases: Medline, Embase, SportDiscus, and Web of Science. Studies involving biotics and protein co-ingestion in humans were included. Primary outcomes were blood AA concentration and pharmacokinetic parameters: area under the curve (AUC), maximum concentration (Cmax), and time to maximum concentration (Tmax). Risk of bias and overall quality of evidence were assessed using the Cochrane Rob-2 and the GRADE tool, respectively.
RESULTS:
18 studies met the inclusion criteria: 6 on microbial proteases (n=153), 11 on probiotics (n=411), and 1 on postbiotics (n=16). 16 studies included young adults (18–36 y), 2 included older adults (40–75 y), and 5 incorporated resistance exercise. 4 studies on microbial protease reported increased early postprandial AUC (within 2 h) for total (TAA), essential (EAA), and branched-chain AA (BCAA) following plant or animal protein co-ingestion. 4 studies reported no difference in blood AA Cmax, whereas 2 studies reported higher Cmax for TAA and select individual AA with animal protein. 1 study reported faster Tmax for leucine in an animal-based mixed meal. All 11 probiotic studies used long-term supplementation (14-84 d) protocols. 2 probiotic studies evaluated blood AA concentrations in the post-absorptive state and reported higher basal concentrations for BCAA, EAA, TAA with animal protein. 9 probiotic studies assessed postprandial AA concentrations and pharmacokinetic parameters. Of these, 6 studies reported higher blood AUC and Cmax for EAA, BCAA, and TAA with plant or animal protein, while 3 studies found no difference on blood AA concentrations or pharmacokinetic parameters. The postbiotic study reported a higher percent increase from baseline for TAA and select individual AA and a slower Tmax for TAA.
CONCLUSION:
Overall, co-ingestion of microbial enzymes, probiotics, and postbiotics with dietary protein can enhance postprandial blood AA concentrations and select AA pharmacokinetic parameters. These findings support the notion that application of select oral biotics may represent a nutritional strategy to enhance dietary protein digestion in humans.