Prolonged Intake of Isoflavone- and Saponin-Containing Soybean Extract (Nijiru) Supplement Enhances Circulating γ-Carboxylated Osteocalcin Concentrations in Healthy Individuals

Abstract

The effect of nijiru, which is a by-product of the processing of soybeans to make the fermented soybeans called natto, on circulating blood chemistry levels related to calcium and bone metabolism in healthy individuals was investigated. Twelve volunteers (six men and six women) were received nijiru twice a day for 60 days at a dose of 1500 mg (6 tablets) per day. The serum γ-carboxylated osteocalcin concentration was significantly increased by the intake of nijiru in both men and women to about 2-fold that in the control group. The serum calcium concentration was significantly decreased by nijiru supplementation in women, and the serum inorganic phosphorus concentration was significantly reduced in both men and women. However, the intake of, nijiru did not have a significant effect on serum glucose, nitrogen urea, albumin, free cholesterol, triglyceride, high-density lipoprotein cholesterol, and γ-glutamyltranspeptidase concentrations in men or women, indicating that liver and renal function is not affected by nijiru supplementation. The results of the present study suggest that the intake of isoflavone- and saponin-containing nijiru can stimulate the γ-carboxylation of osteocalsin, which plays an important role in bone formation and mineralization, in healthy individuals.