Effects of Whey Protein Supplementation on Muscle Damage, Hepatic Stress, and Inflammatory Markers in Power‐ and Endurance‐Trained Athletes

ABSTRACT

This study investigated the effects of 8 weeks of whey protein supplementation (30 g/day) on biomarkers of liver function, inflammation, and muscle damage in trained power‐trained (predominantly speed‐power/anaerobic‐power disciplines) and endurance‐trained athletes, in a randomized, double‐blind, placebo‐controlled design. Fifty‐nine male athletes were stratified into power ( n  = 30) and endurance ( n  = 29) groups, then randomly assigned to a whey protein group (WG) or a placebo control group (CG). Biomarkers assessed pre‐ and post‐intervention included alanine aminotransferase (ALT), aspartate aminotransferase (AST), C‐reactive protein (CRP), and creatine kinase (CK). Significant reductions in ALT, AST, and CK were observed in both endurance‐ and power‐trained athletes after supplementation ( p  = 0.001, p  = 0.015, p  = 0.001, and p  = 0.003 respectively), indicating attenuated hepatic and muscular stress. Among the four biomarkers, only ALT displayed a statistically significant three‐way interaction (Time × Supplementation × Training modality; p  = 0.003), identifying it as the sole marker showing a genuine modality‐specific differential response to supplementation. A significant within‐group reduction in CRP was additionally observed in the supplemented power‐trained athletes ( p  = 0.039), whereas endurance athletes showed only minor, non‐significant changes; because the omnibus three‐way interaction for CRP was not significant, this finding is reported as a within‐group trend rather than evidence of a differential effect between modalities. Placebo groups demonstrated stable or increased enzyme and CRP values, particularly in endurance athletes. These findings suggest that whey protein may attenuate exercise‐induced hepatic and muscular stress across training modalities, with a modality‐specific effect on hepatic stress markers (ALT) observed in power‐trained athletes. The results highlight whey protein's potential as a nutritional aid to promote recovery and physiological adaptation, possibly mediated by antioxidant and anti‐inflammatory mechanisms. Further studies are warranted to examine long‐term outcomes and dose‐response effects across different training profiles.