It is known that beside synthetic Angiotensin-Converting Enzyme (ACE) inhibitors also several peptides from food proteins inhibit ACE. We have identified the highly potent ACE-inhibitor IW (IC50= 0.7 mM) in infant formula with hydrolysed whey protein. IW represents the most effective ACE-inhibiting peptide which has ever been detected in food items. We studied the hypothesis that intake (for 15 weeks) of the potent inhibitory peptide IW is associated with lowering of arterial hypertension and myocardial remodelling in spontaneously hypertensive rats (SHR). Methods: SHR (n= 48) were divided into four groups with different supplements in their food pellets: placebo group without any supplement (PL), captopril (CA) group, IP group with IW (1.6 mg/d and kg BW), and a control group (CP) with intact whey protein in the food pellets. Systolic blood pressure (SBP) was monitored non-invasively via the tail cuff method. At week 15 coronary dilator reserve was determined in isolated heart preparations. Results: At the beginning SBP was similar in all groups (232 ± 5 mmHg) and increased in the typical range in the PL- and CP-groups. A significant decrease in SBP was shown for the CA- (mean:-28 ± 4 mmHg) and the HA-group (mean:-17 ± 4 mmHg). At week 15 heart mass was significant lower in HA- (92 ± 1%) and CA-group (83 ± 2%). Coronary flow reserve was improved in CA- and HA- versus CP-group. To evaluate a direct vasodilating effect of IW and Captopril isolated aortic rings were studied in the myograph. These measurements revealed the absence of a direct vasodilating effect. Conclusions: Neither IW nor Captopril showed a direct vasodilating effect. SBP was decreased after IW intake similar to that of ACE-inhibitors. Improvement of arterial hypertension is associated with myocardial remodelling. Products containing IW are a highly effective dietary supplement that may support arterial blood pressure reduction in hypertensives.