Antihypertensive Effects of Natto, a Traditional Japanese Fermented Food, in Spontaneously Hypertensive Rats

Abstract

Natto is a popular traditional Japanese food made by fermenting steamed soybeans with Bacillus subtilis natto. It has long been thought that natto is effective in preventing hypertension. But there have not been any reports demonstrating in vivo antihypertensive effects of natto. In this study, we demonstrate for the first time the antihypertensive activity of natto in vivo. We determined optimal conditions for producing natto with the highest angiotensin I converting enzyme (ACE) inhibitory activity. An ACE inhibitor partially purified from natto was orally administered as a single dose (1 mg, 10 mg, and 100 mg/kg body weight) in spontaneously hypertensive rats, and then their blood pressure was measured five times every hour after administration. The administration of the inhibitor, even at the lowest dose, resulted in a significant decrease in blood pressure 4 h after administration. Thus, the ACE inhibitor from natto appears to moderately reduce blood pressure relative to increases in dosage.