Grass-Fed and Non-Grass-Fed Whey Protein Supplementation and High-Intensity Eccentric Exercise Do Not Affect Arterial Stiffness and Systemic Hemodynamics in Resistance-Trained Individuals

Introduction: Dairy products from pasture-raised grass-fed cows are known for their higher anti-inflammatory and antioxidant content, which may enhance vascular modulation compared to products from grain-fed cows. Given that eccentric muscle loading (EML) and the resulting exercise-induced muscle damage (EIMD) may temporarily disrupt vascular homeostasis, this study tested the hypothesis that whey protein from pasture-raised grass-fed cows (PRWP) would improve markers of vascular recovery compared to conventional whey protein (CWP) or a non-protein control (NPC). Methods: A randomized, double-blind, placebo-controlled study was used to test 39 resistance-trained participants (66% male, PRWP, n = 14; CWP, n = 12; NPC, n = 13). EIMD was induced via an eccentric barbell back squat protocol, followed by vascular assessments (peripheral/central blood pressure and carotid-femoral pulse wave velocity using applanation tonometry) at 24, 48, and 72 hours post-EML. Results: No between-group differences in blood pressure or vascular measures were observed pre-EML. However, a significant interaction was observed 48 hours post-EML, with diastolic blood pressure (DBP) elevated in the PRWP group (PRWP, 77 ± 11 mm Hg; CWP, 66 ± 9 mm Hg; NPC, 67 ± 10 mm Hg; P = 0.011). Pulse wave velocity did not differ significantly between groups (P = 0.598), visit (P = 0.753), or group-by-visit interaction (P = 0.418). No additional differences in blood pressure or vascular assessments were observed post-EML. Conclusions: Unexpectedly, PRWP increased DBP 48 hours post-EML, without any observed benefit in vascular recovery markers. Participants' training backgrounds may have reduced the sensitivity to detect EML-induced vascular disruptions.