A Meta-Analytic Comparison of Protein Hydrolysate and Intact Protein Effects on Postexercise Plasma Insulin and Glucagon Responses in Healthy, Trained Males

Abstract

Purpose: To conduct a meta-analysis to evaluate how protein hydrolysate and carbohydrate (CHO) mixtures compare with intact protein CHO mixtures in regards to post-exercise plasma insulin and glucagon responses in healthy endurance trained male participants. Methods: Studies were identified via the online databases PubMed, Google scholar, Cochrane, and MDPI. Investigations that measured insulin and/or glucagon via needle biopsy during recovery (with the first measurement taken ≤ 30 min post-exercise) following a standardized exercise bout (any type) with the ingestion of carbohydrate only vs. carbohydrate and protein (pro) were included in this meta-analysis. Random-effects meta-analyses (CHO+pro vs. CHO only) and subgroup analyses (CHO+hydrolyzed pro vs. CHO+intact pro) were conducted to evaluate intervention efficacy. Results: Overall, 33 trials derived from 20 articles were included in this meta-analysis. Of which 9 trials were included for insulin area under curve (AUC), 9 trials were included for muscle fractional synthesis rate (FSR), 30 trials were included for plasma glucose peaks over time, 6 trials were included for muscle glycogen synthesis rate, 8 trials were included for muscle glycogen storage, and 5 trials were included for plasma glucagon peaks over time. The ingestion of CHO+pro induced significant higher insulin peaks than the ingestion of CHO only from 30 minutes to 240 minutes postexercise (30-180 min:p < 0.001, 210-240 min: p < 0.01). The ingestion of CHO+pro also induced significantly higher insulin AUC than the ingestion of CHO only (the standard mean difference was 2.70, 95% CI 1.25–4.16, p < 0.001; I2 = 90.82%) and muscle FSR (the standard mean difference was 2.66, 95% CI 1.27–4.05, p < 0.001; I2 = 92.82%). No differences on insulin peaks over time between the ingestion of CHO+intact pro and CHO+hydrolyzed pro were found by the subgroup analyses (p > 0.05). On the other hand, although the ingestion of CHO+pro reported significantly lower plasma glucose peaks from 30 to 120 minutes postexercise (30-90 min: p < 0.001; 120 min: p < 0.01) than the ingestion of CHO only, no difference on muscle glycogen synthesis rate was found between the intervention and control group (The standard mean difference was 0.82, 95% CI (-0.41)–2.05, p > 0.05; I2 = 85.53%). Finally, no differences on glucagon peaks between the intervention and control group from 30 to 60 minutes were found (p > 0.05). Conclusion: The co-ingestion of CHO+pro should be a better strategy for recovery for endurance-type male athletes than the ingestion of CHO