Japanese black vinegar Kurozu promotes lifespan and healthspan extension in Caenorhabditis elegans

Kurozu, a traditional Japanese black vinegar (JBV), is produced from steamed unpolished rice, koji, and water through saccharification, alcoholic fermentation, and acetic fermentation. These processes result in a vinegar rich in amino acids, vitamins, organic acids, and proteins. While Kurozu has demonstrated benefits, including anti-oxidative and anti-adipogenic activities, its effects on health at the organismal level remain poorly understood. This study aimed to evaluate the impact of Kurozu on healthspan of Caenorhabditis elegans (C. elegans) using the C. elegans Health lifespan Auto-monitoring System (C-HAS). Kurozu concentrated liquid (KCL) was tested at concentrations ranging from 0.005% to 0.5%. Results showed that 0.5% KCL significantly extended lifespan and healthspan, particularly when heat-killed (HK) E. coli OP50 was provided as the food source. In contrast, the lifespan- and healthspan-extending effects at 0.5% KCL were abolished when live E. coli was used as the food source. This suggests that active components in KCL may be metabolized by live bacteria, diminishing their beneficial effects. Further reproducibility tests at 0.5% and 1% KCL concentrations confirmed the healthspan-extending effects under conditions of dead bacterial feeding. This study highlights the health-promoting impact of KCL and provides new insights into its role as a functional food ingredient.