Central arterial compliance plays an important role in the functional abilities of the vasculature. Two active tripeptides, valine-proline-proline and isoleucine-proline-proline, were isolated from sour milk and were referred to as lactotripeptides (LTP). Because LTP appears to act as an angiotensin-converting enzyme inhibitor, it is plausible to hypothesize that LTP improves arterial compliance. We determined the effects of LTP ingestion alone or in combination with regular aerobic exercise on arterial compliance. A total of 55 postmenopausal women (50-65 yr old) were randomly divided into four groups: placebo, LTP, exercise and placebo (Ex + placebo), or exercise and LTP (Ex + LTP). LTP or placebo was administered orally for 8 wk. The exercise groups completed an 8-wk moderate aerobic exercise intervention. There were no differences in baseline arterial compliance and most other key dependent variables among the groups. Carotid arterial compliance increased significantly in the LTP (0.93 + or - 0.07 vs. 0.99 + or - 0.08 mm(2)/mmHg x 10(-1)), Ex + placebo (0.92 + or - 0.04 vs. 1.00 + or - 0.05 mm(2)/mmHg x 10(-1)), and Ex + LTP groups (0.86 + or - 0.06 vs. 1.00 + or - 0.06 mm(2)/mmHg x 10(-1)), whereas no such changes were observed in the placebo control group (0.86 + or - 0.06 vs. 0.85 + or - 0.07 mm(2)/mmHg x 10(-1)). The magnitude of increases in carotid arterial compliance was significantly greater in the Ex + LTP group (19 + or - 4%) than in other groups. The improvements in arterial compliance with LTP were associated with the corresponding reductions in arterial blood pressure and plasma angiotensin II concentrations. We concluded that LTP ingestion improves carotid arterial compliance and that the combination of LTP ingestion and regular exercise is additive and synergistic in improving arterial compliance in postmenopausal women.