Are Umezu polyphenols in the Japanese plum (Prunus mume) protective against mild hypertension and oxidation? Evidence from a double-blind randomized placebo-controlled trial

Medications or lifestyle changes to prevent or improve hypertension often press considerable efforts on patients suffering from mild hypertension. Beverages including Umezu polyphenols (UP), polyphenols in Japanese plums, may help them to control their blood pressure. Healthy medical students, workers, and community dwellers who had some concerns about their blood pressure were randomized in a doubleblind manner into UP ingesting and placebo groups. The first two samples (medical students and workers) were placed in a preliminary study, and based on the results from that study, and the dose of UP for the community dwellers was determined. All three groups were followed for 5 weeks, and blood pressure, as well as biochemical markers related to hypertension and atherosclerosis and self-perceived quality-of-life outcomes, was monitored during that period. Group × time interactions on blood pressure changes were examined. For the community dwellers, blood pressure changes did not significantly differ between the UP ingesting and placebo groups. And although studies of students and workers showed subtle differences in blood pressure among the UP and placebo groups, a dose-dependent effect of UP on decreasing blood pressure could not be confirmed. On the other hand, anti-oxidative effects of UP were confirmed especially among male drinkers who were community dwellers. For the community dwellers, self-perceived physical health significantly improved in those who ingested UP. In conclusion, UP might prevent oxidation. A longer monitoring period as well as a higher dose of UP might enable us to confirm effects of UP against hypertension.