Limited evidence suggests that dairy whey protein may be the major dairy component that is responsible for health benefits currently associated with increased dairy consumption. Whey proteins may reduce blood pressure and improve cardiovascular health. This study evaluated the effects of whey protein supplementation on blood pressure, vascular function and inflammatory markers compared to casein and glucose (control) supplementation in overweight/obese individuals. The subjects were randomized to either whey protein, casein or glucose supplementation for 12 weeks according to a parallel design. In all, 70 men and women with a mean (+/-s.e.m.) BMI (kg/m(2)) of 31.3 +/- 0.8 completed the study. Systolic blood pressure (SBP) decreased significantly at week 6 compared to baseline in the whey and casein groups, (P = 0.028 and P = 0.020, respectively) and at week 12 (P = 0.020, and P = 0.017, respectively). Diastolic blood pressure (DBP) decreased significantly compared to baseline in the whey and casein groups (P = 0.038 and P = 0.042, respectively) at week 12. DBP decreased significantly in the whey and casein groups (P = 0.025, P = 0.038, respectively) at week 12 compared to the control group. Augmentation index (AI) was significantly lower from baseline at 12 weeks (P = 0.021) in the whey group. AI decreased significantly in the whey group at 12 weeks compared to control (P = 0.006) and casein (P = 0.006). There were no significant changes in inflammatory markers within or between groups. This study demonstrated that supplementation with whey protein improves blood pressure and vascular function in overweight and obese individuals.