Background: Available data suggest that substitution of refined carbohydrate in the diet with protein and fiber may benefit blood pressure. Lupin kernel flour is high in protein and fiber and low in carbohydrate.Objective: Our objective was to determine the effects on blood pressure of a diet moderately higher in dietary protein and fiber achieved by substituting lupin kernel flour for wheat flour in bread.Design: Overweight and obese men and women (n = 88) were recruited to a 16-wk parallel-design study. Participants were randomly assigned to replace 15–20% of their usual daily energy intake with white bread (control) or lupin kernel flour–enriched bread (lupin). Measurements, including 24-h ambulatory blood pressure, were taken at baseline and 16 wk.Results: Seventy-four participants (37 per group) completed the intervention. Baseline mean (±SD) systolic/diastolic blood pressures were 122.1 ± 9.6/70.8 ± 7.2 mm Hg (control) and 120.1 ± 9.5/71.2 ± 5.9 mm Hg (lupin). For lupin relative to control, the estimated mean (95% CI) net differences in protein, fiber, and carbohydrate intakes during the intervention were 13.7 g/d (95% CI: 2.3, 25.0 g/d), 12.5 g/d (95% CI: 8.8, 16.2 g/d), and −19.9 g/d (95% CI: −45.2, 5.5 g/d), respectively. Differences in systolic blood pressure, diastolic blood pressure, pulse pressure, and heart rate were −3.0 mm Hg (95% CI: −5.6, −0.3 mm Hg; P = 0.03), 0.6 mm Hg (95% CI: −1.0, 2.2 mm Hg; P = 0.47), −3.5 mm Hg (95% CI: −5.3, −1.8 mm Hg; P <0.001), and 0.0 beats/min (95% CI: −1.7, 1.7 beats/min; P = 0.99), respectively.Conclusions: Increasing protein and fiber in bread with lupin kernel flour may be a simple dietary approach to help reduce blood pressure and cardiovascular risk. This trial was registered at the Australian New Zealand Clinical Trials Registry at http://www.anzctr.org.au/trial_view.aspx?ID=1014 as ACTRN12606000034538 on 25 January 2006.