This supplement contains vitamin K2, (menaquinone-7) extracted from natto. Traditionally from Japan, natto consists of fermented soybeans and characterized by a slimy, sticky, and stringy texture. Natto contains far more vitamin K2 than any other food ever tested. About 90 percent of natto’s K2 is in MK-7 form, the type of menaquinone that has the strongest evidence for bone health.

Vitamin K is needed for proper bone formation and blood clotting. In both cases, vitamin K does this by helping the body transport calcium. Vitamin K is used by the medical community when treating an overdose of the drug warfarin, used to treat blood clots and to lower the chance of blood clots forming in the body. Also, doctors prescribe vitamin K to prevent excessive bleeding in people taking warfarin but requiring surgery.

Vitamin K2 deficiency, which causes uncontrolled bleeding, is rare, except in people with certain malabsorption diseases. However, there are reports of severe vitamin K deficiency developing in hospitalized patients who had poor food intake and were receiving an excess of antibiotics.