The intake of natto, an excellent source of vitamin K2, may reduce bone fracture risk. - GreenMedInfo Summary

Intervention studies and meta-analyses have shown that vitamin D(3) at 700-800 IU/day decreases the fracture incidence. Higher phylloquinone (vitamin K(1)) intake or "natto" intake was associated with lower fracture incidence. In contrast, current intake of vitamin D and K in Japanese is likely to be unsatisfactory for preventing fracture. The intake of fish, abundant in vitamin D(3) is encouraged. Regarding vitamin K, "natto" intake is strongly recommended, since it contains extraordinary amount of menaquinone-7. Phylloquinone in green vegetables would be efficiently absorbed when cooked with oil. Thus Japanese traditional foods seem to be appropriate for bone health.