Japanese fermented soybean food as the major determinant of the large geographic difference in circulating levels of vitamin K2: Possible implications for hip-fracture risk

Increasing evidence indicates a significant role for vitamin K in bone meta bolism and osteoporosis. In this study, we found a large geographic differe nce in serum vitamin K2 (menaquinone-7; MK-7) levels in postmenopausal wome n. Serum MK-7 concentrations were 5.26 +/- 6.13 ng/mL. (mean +/- SD) in Jap anese women ill Tokyo, 1.22 +/- 1.85 in Japanese women in Hiroshima, and 0. 37 +/- 0.20 in British women. We investigated the effect of Japanese fermen ted soybean food, natto, on serum vitamin K levels. Natto contains a large amount of MK-7 and is eaten frequently in eastern (Tokyo) but seldom in wes tern (Hiroshima) Japan. Serum concentrations of MK-7 were significantly hig her in frequent natto eaters, and natto intake resulted in a marked, sustai ned increase in serum MK-7 concentration. We analyzed the relation between the regional difference in natto intake and fracture incidence. A statistic ally significant inverse correlation was found between incidence of hip fra ctures in women and natto consumption in each prefecture throughout Japan. These findings indicate that the large geographic difference in MK-7 levels may be ascribed, at least in part, to natto intake and suggest the possibi lity that higher MK-7 level resulting from natto consumption may contribute to the relatively lower fracture risk in Japanese women. (C) Elsevier Scie nce Inc. 2001.