Impact of different protein sources on acute muscle protein synthesis following resistance training: a systematic review with standard and dose–response network meta-analyses

Background The combination of protein intake and resistance training (RT) plays a pivotal role in stimulating muscle protein synthesis (MPS), yet the impact of different protein sources remains an area of active investigation. Therefore, a systematic review incorporating standard and dose‒response network meta-analyses was performed.Methods Systematic literature search was conducted in PubMed, EBSCOhost (including MEDLINE, SPORTDiscus, CINAHL), and Scopus. Eligible studies included healthy adults (≥18 years) who were undergoing acute resistance exercise followed by a single protein bolus (any type or dose, except blends or enriched with anabolic agents). Muscle biopsies were required before and after RT/protein intake without additional food in between. Trials measuring hourly MPS rates via tracer techniques were included (n = 51).Results In the standard network meta-analysis (NMA), native whey (P-score = 0.81, MD = 0.05% [0.00; 0.10]), pea protein (0.77, MD = 0.05% [−0.02; 0.11]), whole egg protein (0.72, MD = 0.04% [−0.01; 0.09]), mycoprotein (0.66, MD = 0.03% [−0.02; 0.08]), and whey protein (0.58, MD = 0.02% [0.01; 0.04]) ranked highest for estimated efficacy in stimulating post-RT hourly MPS (in descending order) (only whey protein showed a statistically significant effect) with low to moderate certainty of evidence. Dose‒response NMA revealed that certain animal- (native whey and whole egg protein) and plant- (pea and mycoprotein) based protein sources to show the highest predicted MPS responses with doses of 18–25 g.Conclusions Animal- (native whey, whey, whole egg) and plant-based (pea, mycoprotein) proteins ranked similarly for estimated acute MPS stimulation when combined with RT; however, only whey protein showed a statistically significant effect, and protein sources represented by few studies should be interpreted with caution.