Objectives　A previous study has examined the antihypertensive effect of the bovine casein-derived peptide Met-Lys-Pro（MKP）in vitro and in vivo. We evaluated the effect of MKP in lowering blood pressure in subjects with high-normal blood pressure and grade 1 hypertension.
Methods　In total, 65 subjects with high-normal blood pressure and grade 1 hypertension participated in a randomized, double-blind, placebo-controlled, parallel-group trial for 12 weeks. Subjects were allocated to four groups: low-dose（50μg MKP）, moderate-dose（100μg MKP）, high-dose（200μg MKP）, and placebo group.
Results　Systolic blood pressure（SBP）was significantly lower in the moderate-dose group than in the placebo group at 4 and 12 weeks. Diastolic blood pressure was significantly lower in the moderate-dose group than in the placebo group at 4, 8, and 12 weeks. In a subgroup analysis of subjects with high-normal blood pressure, SBP was significantly lower in the moderate-dose group than in the placebo group at 4 weeks. No serious adverse events related to test product ingestion were observed in any group.
Conclusions　These results suggest that MKP has a beneficial effect on lowering blood pressure in subjects with high-normal blood pressure and grade 1 hypertension.